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Ai2 1,336

206215269

10.1111/NPH.12690

Current issues in the evolutionary ecology of ant-plant symbioses.

Ant-plant symbioses involve plants that provide hollow structures specialized for housing ants and often food to ants. In return, the inhabiting ants protect plants against herbivores and sometimes provide them with nutrients. Here, we review recent advances in ant-plant symbioses, focusing on three areas. First, the nutritional ecology of plant-ants, which is based not only on plant-derived food rewards, but also on inputs from other symbiotic partners, in particular fungi and possibly bacteria. Food and protection are the most important 'currencies' exchanged between partners and they drive the nature and evolution of the relationships. Secondly, studies of conflict and cooperation in ant-plant symbioses have contributed key insights into the evolution and maintenance of mutualism, particularly how partner-mediated feedbacks affect the specificity and stability of mutualisms. There is little evidence that mutualistic ants or plants are under selection to cheat, but the costs and benefits of ant-plant interactions do vary with environmental factors, making them vulnerable to natural or anthropogenic environmental change. Thus, thirdly, ant-plant symbioses should be considered good models for investigating the effects of global change on the outcome of mutualistic interactions.

New Phytologist

67864023

10.1038/S41598-019-39583-7

Viscosin-like lipopeptides from frog skin bacteria inhibit Aspergillus fumigatus and Batrachochytrium dendrobatidis detected by imaging mass spectrometry and molecular networking

Amphibian populations worldwide have declined and in some cases become extinct due to chytridiomycosis, a pandemic disease caused by the fungus Batrachochytrium dendrobatidis; however, some species have survived these fungal epidemics. Previous studies have suggested that the resistance of these species is due to the presence of cutaneous bacteria producing antifungal metabolites. As our understanding of these metabolites is still limited, we assessed the potential of such compounds against human-relevant fungi such as Aspergillus. In this work we isolated 201 bacterial strains from fifteen samples belonging to seven frog species collected in the highlands of Panama and tested them against Aspergillus fumigatus. Among the 29 bacterial isolates that exhibited antifungal activity, Pseudomonas cichorii showed the greatest inhibition. To visualize the distribution of compounds and identify them in the inhibition zone produced by P. cichorii, we employed MALDI imaging mass spectrometry (MALDI IMS) and MS/MS molecular networking. We identified viscosin and massetolides A, F, G and H in the inhibition zone. Furthermore, viscosin was isolated and evaluated in vitro against A. fumigatus and B. dendrobatidis showing MIC values of 62.50 µg/mL and 31.25 µg/mL, respectively. This is the first report of cyclic depsipeptides with antifungal activity isolated from frog cutaneous bacteria.

Scientific Reports

28491967

10.1086/512137

Adaptive Advantages of Cooperative Courtship for Subordinate Male Lance‐Tailed Manakins

Male lance‐tailed manakins (Chiroxiphia lanceolata) cooperate in complex courtship displays, but the dominant (alpha) partner monopolizes mating opportunities. This raises the question of why subordinates (betas) cooperate. Three nonexclusive hypotheses explain the adaptive basis of helping behavior by subordinate males: cooperation may increase (1) subordinates’ immediate reproductive success, (2) the reproductive success of close relatives, or (3) subordinates’ chances of future reproduction. I demonstrated that beta males rarely sired chicks and were unrelated to their alpha partners but received delayed direct benefits from cooperation; betas had an increased probability of becoming an alpha when compared to males that had not been betas. To investigate the mechanism by which betas attain these adaptive benefits, I examined betas’ success in replacing their alpha partners both in natural turnover events and when alphas were experimentally removed. Beta males did not consistently inherit alpha roles in the same territories where they served their beta tenure, arguing that queuing for status does not fully explain the benefits of cooperation for betas. Instead, betas may be apprenticing to develop effective and appropriate displays that enhance their subsequent success as alphas. Complex social affiliations appear to mediate selective pressure for cooperation in this species.

The American Naturalist

25747841

10.1007/S00265-005-0019-6

The use of waggle dance information by honey bees throughout their foraging careers

We studied the extent to which worker honey bees acquire information from waggle dances throughout their careers as foragers. Small groups of foragers were monitored from time of orientation flights to time of death and all in-hive behaviors relating to foraging were recorded. In the context of a novice forager finding her first food source, 60% of the bees relied, at least in part, on acquiring information from waggle dances (being recruited) rather than searching independently (scouting). In the context of an experienced forager whose foraging has been interrupted, 37% of the time the bees resumed foraging by following waggle dances (being reactivated) rather than examining the food source on their own (inspecting). And in the context of an experienced forager engaged in foraging, 17% of the time the bees initiated a foraging trip by following a waggle dance. Such dance following was observed much more often after an unsuccessful than after a successful foraging trip. Successful foragers often followed dances just briefly, perhaps to confirm that the kind of flowers they had been visiting were still yielding forage. Overall, waggle dance following for food discovery accounted for 12–25% of all interactions with dancers (9% by novice foragers and 3–16% by experienced foragers) whereas dance following for reactivation and confirmation accounted for the other 75–88% (26% for reactivation and 49–62% for confirmation). We conclude that foragers make extensive use of the waggle dance not only to start work at new, unfamiliar food sources but also to resume work at old, familiar food sources.

Behavioral Ecology and Sociobiology

205064759

10.1038/47396

Marine iguanas shrink to survive El Niño

Changes in bone metabolism enable these adult lizards to reversibly alter their length.

Nature

16581286

10.1098/RSBL.2005.0350

Sensitivity to dimethyl sulphide suggests a mechanism for olfactory navigation by seabirds

Petrels, albatrosses and other procellariiform seabirds have an excellent sense of smell, and routinely navigate over the world's oceans by mechanisms that are not well understood. These birds travel thousands of kilometres to forage on ephemeral prey patches at variable locations, yet they can quickly and efficiently find their way back to their nests on remote islands to provision chicks, even with magnetic senses experimentally disrupted. Over the seemingly featureless ocean environment, local emissions of scents released by phytoplankton reflect bathymetric features such as shelf breaks and seamounts. These features suggest an odour landscape that may provide birds with orientation cues. We have previously shown that concentrated experimental deployments of one such compound, dimethyl sulphide (DMS), attracts procellariiforms at sea, suggesting that some species can use it as a foraging cue. Here we present the first physiological demonstration that an Antarctic seabird can detect DMS at biogenic levels. We further show that birds can use DMS as an orientation cue in a non-foraging context within a concentration range that they might naturally encounter over the ocean.

Biology Letters

13957870

10.1039/B505796P

Cell-cell communication in Gram-negative bacteria.

Over the last decade or so, a wealth of research has established that bacteria communicate with one another using small molecules. These signals enable the individuals in a population to coordinate their behaviour. In the case of pathogens, this behaviour may include decisions such as when to attack a host organism or form a biofilm. Consequently, such signalling systems are excellent targets for the development of new antibacterial therapies. In this review, we assess how Gram-negative bacteria use small molecules for cell-cell communication, and discuss the main approaches that have been developed to interfere with it.

Molecular BioSystems

10262345

10.1007/S11157-006-9118-8

Biodeterioration of crude oil and oil derived products: a review

Biodeterioration of crude oil and oil fuels is a serious economic and an environmental problem all over the world. It is impossible to prevent penetration of microorganisms in oil and fuels both stored in tanks or in oilfields after drilling. Both aerobic and anaerobic microorganisms tend to colonise oil pipelines and oil and fuel storage installations. Complex microbial communities consisting of both hydrocarbon oxidizing microorganisms and bacteria using the metabolites of the former form an ecological niche where they thrive. The accumulation of water at the bottom of storage tanks and in oil pipelines is a primary prerequisite for development of microorganisms in fuels and oil and their subsequent biological fouling. Ability of microorganisms to grow both in a water phase and on inter-phase of water/hydrocarbon as well as the generation of products of their metabolism worsen the physical and chemical properties of oils and fuels. This activity also increases the amount of suspended solids, leads to the formation of slimes and creates a variety of operational problems. Nowadays various test-systems are utilized for microbial monitoring in crude oils and fuels; thus allowing an express determination of both the species and the quantities of microorganisms present. To suppress microbial growth in oils and fuels, both physico-mechanical and chemical methods are applied. Among chemical methods, the preference is given to substances such as biocides, additives, the anti-freezing agents etc that do not deteriorate the quality of oil and fuels and are environmentally friendly. This review is devoted to the analysis of the present knowledge in the field of microbial fouling of crude oils and oil products. The methods utilized for monitoring of microbial contamination and prevention of their undesirable activities are also evaluated. The special focus is given to Russian scientific literature devoted to crude oil and oil products biodeterioration.

Reviews in Environmental Science and Bio\/technology

19136252

10.1016/J.CUB.2012.01.055

The function of the sawfish's saw

Summary Jawed fishes that possess an elongated rostrum use it to either sense prey or to manipulate it, but not for both. The billfish rostrum, for instance, lacks any sensory function and is used to stun prey [1], while paddlefishes use their rostrum to detect and orient towards electric fields of plankton [2]. Sturgeons search through the substrate with their electroreceptive rostrum, and engulf prey by oral suction [2]. Here, we show that juvenile freshwater sawfish Pristis microdon are active predators that use their toothed rostrum — the saw — to both sense prey-simulating electric fields and capture prey. Prey encountered in the water column is attacked with lateral swipes of the saw that can stun and/or impale it. We compare sawfish to shovelnose rays, which share a common shovelnose ray-like ancestor [3] and lack a saw.

Current Biology

14882384

10.1016/J.NEUCOM.2006.11.013

Super-lampreys and wave energy: Optimised control of artificially-evolved, simulated swimming lamprey

Propulsion in the lamprey, an eel-like fish, is governed by activity in its spinal neural network (called a central pattern generator (CPG)). This CPG is simulated, in accordance with Ekeberg's original model, and optimised alternatives are generated with genetic algorithms (GAs). A two-phase GA is adopted: (1) to evolve neuron-descriptive parameters and synaptic weights of the neural oscillator for a single lamprey segment, (2) to generate interconnections between segments. Results demonstrate that Ekeberg's prototype is not a unique solution and that simpler versions with wider operational ranges can be generated. Evolved solutions outperform the swimming capabilities of a modelled biological organism, as an initial step in understanding how to control wave power devices, with similar motion to the lamprey.

Neurocomputing

86802348

10.1046/J.1442-9993.2003.T01-1-01319.X

Effect of abiotic factors on the foraging strategy of the orb-web spider Argiope keyserlingi (Araneae: Araneidae)

Environmental conditions such as light level, background contrast and temperature might influence a spider's prey capture success and risk of predation. Thus it may often be advantageous for spiders to adjust web-building behaviour in response to variation in these environmental conditions. This hypothesis was examined in a study of the construction of webs and web decorations (conspicuous strands of silk at the hub of the web) of the orb-web spider Argiope keyserlingi. Web decorations are thought to have one or more separate functions. They may attract prey, deter predators or advertise the web to oncoming birds, thus preventing web damage. In this series of experiments, relationships between weather parameters and the construction of webs and web decorations were considered. In complementary laboratory experiments, A. keyserlingi spiders were exposed to two different light levels (700 and 90 lx), background contrasts (black and white) and temperature conditions (20 and 26°C). Of the available weather parameters, only temperature was significantly related to web decorating behaviour but not to web size. In the laboratory, temperature also influenced web-decorating behaviour, and spiders in dim light (700 lx) constructed larger webs and longer decorations. Background contrast did not significantly alter web size or web decorations. These data suggest that when prey availability is reduced at low temperatures, spiders may use web decorations to attract prey to the web. Similarly, in dim light, spiders may build more and larger decorations to increase the visual signal to approaching prey or to advertise the web to oncoming birds.

Austral Ecology

22654532

10.1242/JEB.02051

Anatomically diverse butterfly scales all produce structural colours by coherent scattering

SUMMARY The structural colours of butterflies and moths (Lepidoptera) have been attributed to a diversity of physical mechanisms, including multilayer interference, diffraction, Bragg scattering, Tyndall scattering and Rayleigh scattering. We used fibre optic spectrophotometry, transmission electron microscopy (TEM) and 2D Fourier analysis to investigate the physical mechanisms of structural colour production in twelve lepidopteran species from four families, representing all of the previously proposed anatomical and optical classes of butterfly nanostructure. The 2D Fourier analyses of TEMs of colour producing butterfly scales document that all species are appropriately nanostructured to produce visible colours by coherent scattering, i.e. differential interference and reinforcement of scattered, visible wavelengths. Previously hypothesized to produce a blue colour by incoherent, Tyndall scattering, the scales of Papilio zalmoxis are not appropriately nanostructured for incoherent scattering. Rather, available data indicate that the blue of P. zalmoxis is a fluorescent pigmentary colour. Despite their nanoscale anatomical diversity, all structurally coloured butterfly scales share a single fundamental physical color production mechanism - coherent scattering. Recognition of this commonality provides a new perspective on how the nanostructure and optical properties of structurally coloured butterfly scales evolved and diversified among and within lepidopteran clades.

The Journal of Experimental Biology

2074946

10.1098/RSPB.2002.2210

Self-organized lane formation and optimized traffic flow in army ants

We show how the movement rules of individual ants on trails can lead to a collective choice of direction and the formation of distinct traffic lanes that minimize congestion. We develop and evaluate the results of a new model with a quantitative study of the behaviour of the army ant Eciton burchelli. Colonies of this species have up to 200 000 foragers and transport more than 3000 prey items per hour over raiding columns that exceed 100 m. It is an ideal species in which to test the predictions of our model because it forms pheromone trails that are densely populated with very swift ants. The model explores the influences of turning rates and local perception on traffic flow. The behaviour of real army ants is such that they occupy the specific region of parameter space in which lanes form and traffic flow is maximized.

Proceedings of The Royal Society B: Biological Sciences

4384411

10.1038/NATURE06062

Raptorial jaws in the throat help moray eels swallow large prey

Most bony fishes rely on suction mechanisms to capture and transport prey. Once captured, prey are carried by water movement inside the oral cavity to a second set of jaws in the throat, the pharyngeal jaws, which manipulate the prey and assist in swallowing. Moray eels display much less effective suction-feeding abilities. Given this reduction in a feeding mechanism that is widespread and highly conserved in aquatic vertebrates, it is not known how moray eels swallow large fish and cephalopods. Here we show that the moray eel (Muraena retifera) overcomes reduced suction capacity by launching raptorial pharyngeal jaws out of its throat and into its oral cavity, where the jaws grasp the struggling prey animal and transport it back to the throat and into the oesophagus. This is the first described case of a vertebrate using a second set of jaws to both restrain and transport prey, and is the only alternative to the hydraulic prey transport reported in teleost fishes. The extreme mobility of the moray pharyngeal jaws is made possible by elongation of the muscles that control the jaws, coupled with reduction of adjacent gill-arch structures. The discovery that pharyngeal jaws can reach up from behind the skull to grasp prey in the oral jaws reveals a major innovation that may have contributed to the success of moray eels as apex predators hunting within the complex matrix of coral reefs. This alternative prey transport mode is mechanically similar to the ratcheting mechanisms used in snakes—a group of terrestrial vertebrates that share striking morphological, behavioural and ecological convergence with moray eels.

Nature

20613196

10.1007/S00049-010-0059-X

Defensive and chemical characterization of the froth produced by the cercopid Aphrophora cribrata

Nymphs of the cercopid Aphrophora cribrata cover themselves with a frothy exudate while ingesting sap from their preferred host plant, the eastern white pine, Pinus strobus. Chemical analyses of froth collected from A. cribrata nymphs revealed an array of metabolites belonging to five chemical classes, including fatty acid-derived alcohols, γ-lactones and a single 1-monoacylglycerol, as well as the polyol pinitol and the polyhydroxyalkanoate, poly-3-hydroxybutyrate. Bioassays showed the natural A. cribata froth, as well as a synthetic mixture comprised of representative compound classes identified therein, to be repellent to ants but largely devoid of topical irritancy in tests with cockroaches.

Chemoecology

14260303

10.1098/RSIF.2013.0174

Entrapment of bed bugs by leaf trichomes inspires microfabrication of biomimetic surfaces

Resurgence in bed bug infestations and widespread pesticide resistance have greatly renewed interest in the development of more sustainable, environmentally friendly methods to manage bed bugs. Historically, in Eastern Europe, bed bugs were entrapped by leaves from bean plants, which were then destroyed; this purely physical entrapment was related to microscopic hooked hairs (trichomes) on the leaf surfaces. Using scanning electron microscopy and videography, we documented the capture mechanism: the physical impaling of bed bug feet (tarsi) by these trichomes. This is distinct from a Velcro-like mechanism of non-piercing entanglement, which only momentarily holds the bug without sustained capture. Struggling, trapped bed bugs are impaled by trichomes on several legs and are unable to free themselves. Only specific, mechanically vulnerable locations on the bug tarsi are pierced by the trichomes, which are located at effective heights and orientations for bed bug entrapment despite a lack of any evolutionary association. Using bean leaves as templates, we microfabricated surfaces indistinguishable in geometry from the real leaves, including the trichomes, using polymers with material properties similar to plant cell walls. These synthetic surfaces snag the bed bugs temporarily but do not hinder their locomotion as effectively as real leaves.

Journal of the Royal Society Interface

12639248

10.3389/FMICB.2015.00212

Surfactants tailored by the class Actinobacteria

Globally the change towards the establishment of a bio-based economy has resulted in an increased need for bio-based applications. This, in turn, has served as a driving force for the discovery and application of novel biosurfactants. The class Actinobacteria represents a vast group of microorganisms with the ability to produce a diverse range of secondary metabolites, including surfactants. Understanding the extensive nature of the biosurfactants produced by actinobacterial strains can assist in finding novel biosurfactants with new potential applications. This review therefore presents a comprehensive overview of the knowledge available on actinobacterial surfactants, the chemical structures that have been completely or partly elucidated, as well as the identity of the biosurfactant-producing strains. Producer strains of not yet elucidated compounds are discussed, as well as the original habitats of all the producer strains, which seems to indicate that biosurfactant production is environmentally driven. Methodology applied in the isolation, purification and structural elucidation of the different types of surface active compounds, as well as surfactant activity tests, are also discussed. Overall, actinobacterial surfactants can be summarized to include the dominantly occurring trehalose-comprising surfactants, other non-trehalose containing glycolipids, lipopeptides and the more rare actinobacterial surfactants. The lack of structural information on a large proportion of actinobacterial surfactants should be considered as a driving force to further explore the abundance and diversity of these compounds. This would allow for a better understanding of actinobacterial surface active compounds and their potential for biotechnological application.

Frontiers in Microbiology

17604026

10.1093/JXB/ERM009

Common mycorrhizal networks provide a potential pathway for the transfer of hydraulically lifted water between plants.

Plant roots may be linked by shared or common mycorrhizal networks (CMNs) that constitute pathways for the transfer of resources among plants. The potential for water transfer by such networks was examined by manipulating CMNs independently of plant roots in order to isolate the role(s) of ectomycorrhizal (EM) and arbuscular mycorrhizal fungal (AMF) networks in the plant water balance during drought (soil water potential -5.9 MPa). Fluorescent tracer dyes and deuterium-enriched water were used to follow the pathways of water transfer from coastal live oak seedlings (Quercus agrifolia Nee; colonized by EM and AMF) conducting hydraulic lift (HL) into the roots of water-stressed seedlings connected only by EM (Q. agrifolia) or AMF networks (Q. agrifolia, Eriogonum fasciculatum Benth., Salvia mellifera Greene, Keckiella antirrhinoides Benth). When connected to donor plants by hyphal linkages, deuterium was detected in the transpiration flux of receiver oak plants, and dye-labelled extraradical hyphae, rhizomorphs, mantles, and Hartig nets were observed in receiver EM oak roots, and in AMF hyphae of Salvia. Hyphal labelling was scarce in Eriogonum and Keckiella since these species are less dependent on AMF. The observed patterns of dye distribution also indicated that only a small percentage of mycorrhizal roots and extraradical hyphae were involved with water transfer among plants. Our results suggest that the movement of water by CMNs is potentially important to plant survival during drought, and that the functional ecophysiological traits of individual mycorrhizal fungi may be a component of this mechanism.

Journal of Experimental Botany

207355940

10.2307/1542821

Structural Strengthening of Urchin Skeletons by Collagenous Sutural Ligaments.

Sea urchin skeletons are strengthened by flexible collagenous ligaments that bind together rigid calcite plates at sutures. Whole skeletons without ligaments (removed by bleaching) broke at lower apically applied forces than did intact, fresh skeletons. In addition, in three-point bending tests on excised plate combinations, sutural ligaments strengthened sutures but not plates. The degree of sutural strengthening by ligaments depended on sutural position; in tensile tests, ambital and adapical sutures were strengthened more than adoral sutures. Adapical sutures, which grow fastest, were also the loosest, suggesting that strengthening by ligaments is associated with growth. In fed, growing urchins, sutures overall were looser than in unfed urchins. Looseness was demonstrated visually and by vibration analysis: bleached skeletons of unfed urchins rang at characteristic frequencies, indicating that sound traveled across tightly fitting sutures; skeletons of fed urchins damped vibrations, indicating loss of vibrational energy across looser sutures. Furthermore, bleached skeletons of fed urchins broke at lower apically applied forces than bleached skeletons of unfed urchins, indicating that the sutures of fed urchins had been held together relatively loosely by sutural ligaments. Thus, the apparently rigid dome-like skeleton of urchins sometimes transforms into a flexible, jointed membrane as sutures loosen and become flexible during growth.

The Biological Bulletin

26052962

10.1007/S11120-007-9172-2

Carbon acquisition by diatoms

Diatoms are responsible for up to 40% of primary productivity in the ocean, and complete genome sequences are available for two species. However, there are very significant gaps in our understanding of how diatoms take up and assimilate inorganic C. Diatom plastids originate from secondary endosymbiosis with a red alga and their Form ID Rubisco (ribulose-1,5-bisphosphate carboxylase-oxygenase) from horizontal gene transfer, which means that embryophyte paradigms can only give general guidance as to their C acquisition mechanisms. Although diatom Rubiscos have relatively high CO2 affinity and CO2/O2 selectivity, the low diffusion coefficient for CO2 in water has the potential to restrict the rate of photosynthesis. Diatoms growing in their natural aquatic habitats operate inorganic C concentrating mechanisms (CCMs), which provide a steady-state CO2 concentration around Rubisco higher than that in the medium. How these CCMs work is still a matter of debate. However, it is known that both CO2 and HCO3− are taken up, and an obvious but as yet unproven possibility is that active transport of these species across the plasmalemma and/or the four-membrane plastid envelope is the basis of the CCM. In one marine diatom there is evidence of C4-like biochemistry which could act as, or be part of, a CCM. Alternative mechanisms which have not been eliminated include the production of CO2 from HCO3− at low pH maintained by a H+ pump, in a compartment close to that containing Rubisco.

Photosynthesis Research

1075287

10.1126/SCIENCE.1181369

Comprehensive Mapping of Long-Range Interactions Reveals Folding Principles of the Human Genome

Chromosomal Mapping The conformation of the genome in the nucleus and contacts between both proximal and distal loci influence gene expression. In order to map genomic contacts, Lieberman-Aiden et al. (p. 289, see the cover) developed a technique to allow the detection of all interactions between genomic loci in the eukaryotic nucleus followed by deep sequencing. This technology was used to map the organization of the human genome and to examine the spatial proximity of chromosomal loci at one megabase resolution. The map suggests that the genome is partitioned into two spatial compartments that are related to local chromatin state and whose remodeling correlates with changes in the chromatin state. Chromosomes are organized in a fractal knot-free conformation that is densely packed while easily folded and unfolded. We describe Hi-C, a method that probes the three-dimensional architecture of whole genomes by coupling proximity-based ligation with massively parallel sequencing. We constructed spatial proximity maps of the human genome with Hi-C at a resolution of 1 megabase. These maps confirm the presence of chromosome territories and the spatial proximity of small, gene-rich chromosomes. We identified an additional level of genome organization that is characterized by the spatial segregation of open and closed chromatin to form two genome-wide compartments. At the megabase scale, the chromatin conformation is consistent with a fractal globule, a knot-free, polymer conformation that enables maximally dense packing while preserving the ability to easily fold and unfold any genomic locus. The fractal globule is distinct from the more commonly used globular equilibrium model. Our results demonstrate the power of Hi-C to map the dynamic conformations of whole genomes.

Science

39653214

10.2307/1543529

Egg Longevity and Time-Integrated Fertilization in a Temperate Sea Urchin (Strongylocentrotus droebachiensis)

Recent field experiments have suggested that fertilization levels in sea urchins (and other broadcast spawners that release their gametes into the water column) may often be far below 100%. However, past experiments have not considered the potentially positive combined effects of an extended period of egg longevity and the release of gametes in viscous fluids (which reduces dilution rates). In a laboratory experiment, we found that eggs of the sea urchin Strongylocentrotus droebachiensis had high viability for 2 to 3 d. Fertilization levels of eggs held in sperm-permeable egg baskets in the field and exposed to sperm slowly diffusing off a spawning male increased significantly with exposure from 15 min to 3 h. In a field survey of time-integrated fertilizations (over 24, 48, and 72 h) during natural sperm release events, eggs held in baskets accrued fertilizations over as much as 48 h and attained fairly high fertilization levels. Our results suggest that an extended period of egg longevity and the release of gametes in viscous fluids may result in higher natural fertilization levels than currently expected from short-term field experiments.

The Biological Bulletin

3084773

10.1186/1477-3155-8-12

Naturally occurring nanoparticles from English ivy: an alternative to metal-based nanoparticles for UV protection

BackgroundOver the last decade safety concerns have arisen about the use of metal-based nanoparticles in the cosmetics field. Metal-based nanoparticles have been linked to both environmental and animal toxicity in a variety of studies. Perhaps the greatest concern involves the large amounts of TiO2 nanoparticles that are used in commercial sunscreens. As an alternative to using these potentially hazardous metal-based nanoparticles, we have isolated organic nanoparticles from English ivy (Hedera helix). In this study, ivy nanoparticles were evaluated for their potential use in sunscreens based on four criteria: 1) ability to absorb and scatter ultraviolet light, 2) toxicity to mammalian cells, 3) biodegradability, and 4) potential for diffusion through skin.ResultsPurified ivy nanoparticles were first tested for their UV protective effects using a standard spectrophotometric assay. Next the cell toxicity of the ivy nanoparticles was compared to TiO2 nanoparticles using HeLa cells. The biodegradability of these nanoparticles was also determined through several digestion techniques. Finally, a mathematical model was developed to determine the potential for ivy nanoparticles to penetrate through human skin. The results indicated that the ivy nanoparticles were more efficient in blocking UV light, less toxic to mammalian cells, easily biodegradable, and had a limited potential to penetrate through human skin. When compared to TiO2 nanoparticles, the ivy nanoparticles showed decreased cell toxicity, and were easily degradable, indicating that they provided a safer alternative to these nanoparticles.ConclusionsWith the data collected from this study, we have demonstrated the great potential of ivy nanoparticles as a sunscreen protective agent, and their increased safety over commonly used metal oxide nanoparticles.

Journal of Nanobiotechnology

5851602

10.1242/JEB.160895

Solar-powered ventilation of African termite mounds

ABSTRACT How termite mounds function to facilitate climate control is still only partially understood. Recent experimental evidence in the mounds of a single species, the south Asian termite Odontotermes obesus, suggests that the daily oscillations of radiant heating associated with diurnal insolation patterns drive convective flow within them. How general this mechanism is remains unknown. To probe this, we consider the mounds of the African termite Macrotermes michaelseni, which thrives in a very different environment. By directly measuring air velocities and temperatures within the mound, we see that the overall mechanisms and patterns involved are similar to that in the south Asian species. However, there are also some notable differences between the physiology of these mounds associated with the temporal variations in radiant heating patterns and CO2 dynamics. Because of the difference between direct radiant heating driven by the position of the sun in African conditions, and the more shaded south Asian environments, we see changes in the convective flows in the two types of mounds. Furthermore, we also see that the south Asian mounds show a significant overturning of stratified gases, once a day, while the African mounds have a relatively uniform concentration of CO2. Overall, our observations show that despite these differences, termite architectures can harness periodic solar heating to drive ventilation inside them in very different environments, functioning as an external lung, with clear implications for human engineering. Highlighted Article: Termite mounds harness oscillatory solar heating to drive internal ventilation of metabolic gases, functioning as an external lung for the colony. This passive mechanism has clear implications for human engineering.

The Journal of Experimental Biology

30043369

10.1016/J.JBIOMECH.2010.02.027

Directional dependence of hydroxyapatite-collagen interactions on mechanics of collagen.

Bone is a biological nanocomposite composed primarily of collagen and hydroxyapatite. The collagen molecules self-assemble to from a structure known as a fibril that comprises of about 85-95% of the total bone protein. In a fibril, the molecular level interactions at the interface between molecular collagen and hydroxyapatite nanocrystals have a significant role on its mechanical response. In this study, we have used molecular dynamics and steered molecular dynamics to study directional dependence of deformation response of collagen with respect to the hydroxyapatite surface. We have also studied mechanical response of collagen in the proximity of (0001) and (101 0) surfaces of hydroxyapatite. Our simulations indicate that the mechanics of collagen pulled in different directions with respect to hydroxyapatite is significantly different. Similar results were obtained for collagen pulled in the proximity of different crystallographic surfaces of hydroxyapatite.

Journal of Biomechanics

29901266

10.1007/S11692-009-9069-4

The Ancient Chemistry of Avoiding Risks of Predation and Disease

Illness, death, and costs of immunity and injury strongly select for avoidance of predators or contagion. Ants, cockroaches, and collembola recognize their dead using unsaturated fatty acids (e.g., oleic or linoleic acid) as “necromone” cues. Ants, bees, and termites remove dead from their nests (necrophoric behavior) whereas semi-social species seal off corpses or simply avoid their dead or injured (necrophobic behavior). Alarm and avoidance responses to exudates from injured conspecifics are widespread. This involves diverse pheromones, complex chemistry and learning. We hypothesized that necromones are a phylogenetically ancient class of related signals and predicted that terrestrial Isopoda (that strongly aggregate and lack known dispersants) would avoid body fluids and corpses using fatty acid “necromones.” Isopods were repelled by crushed conspecifics (blood), intact corpses, and alcohol extracts of bodies. As predicted, the repellent fraction contained oleic and linoleic acids and authentic standards repelled several isopod species. We further predicted a priori that social caterpillars (lacking known dispersants) would be repelled by their own body fluids and unsaturated fatty acids. Both tent caterpillars and fall webworms avoided branches treated with conspecific body fluid. Oleic and linoleic acids were also strongly avoided by both species. Necromone signaling appears widespread and likely traces to aquatic ancestors pre-dating the divergence of the Crustacea and Hexapoda at least 420 million years ago.

Evolutionary Biology-new York

205525340

10.1111/J.1462-2920.2009.01948.X

Degradation of alkanes by bacteria.

Pollution of soil and water environments by crude oil has been, and is still today, an important problem. Crude oil is a complex mixture of thousands of compounds. Among them, alkanes constitute the major fraction. Alkanes are saturated hydrocarbons of different sizes and structures. Although they are chemically very inert, most of them can be efficiently degraded by several microorganisms. This review summarizes current knowledge on how microorganisms degrade alkanes, focusing on the biochemical pathways used and on how the expression of pathway genes is regulated and integrated within cell physiology.

Environmental Microbiology

18533264

10.1579/0044-7447-32.6.389

Reserves, Resilience and Dynamic Landscapes

Abstract In a world increasingly modified by human activities, the conservation of biodiversity is essential as insurance to maintain resilient ecosystems and ensure a sustainable flow of ecosystem goods and services to society. However, existing reserves and national parks are unlikely to incorporate the long-term and large-scale dynamics of ecosystems. Hence, conservation strategies have to actively incorporate the large areas of land that are managed for human use. For ecosystems to reorganize after large-scale natural and human-induced disturbances, spatial resilience in the form of ecological memory is a prerequisite. The ecological memory is composed of the species, interactions and structures that make ecosystem reorganization possible, and its components may be found within disturbed patches as well in the surrounding land-scape. Present static reserves should be complemented with dynamic reserves, such as ecological fallows and dynamic successional reserves, that are part of ecosystem management mimicking natural disturbance regimes at the landscape level.

AMBIO: A Journal of the Human Environment

4336747

10.1038/NATURE05733

How swifts control their glide performance with morphing wings

Gliding birds continually change the shape and size of their wings, presumably to exploit the profound effect of wing morphology on aerodynamic performance. That birds should adjust wing sweep to suit glide speed has been predicted qualitatively by analytical glide models, which extrapolated the wing’s performance envelope from aerodynamic theory. Here we describe the aerodynamic and structural performance of actual swift wings, as measured in a wind tunnel, and on this basis build a semi-empirical glide model. By measuring inside and outside swifts’ behavioural envelope, we show that choosing the most suitable sweep can halve sink speed or triple turning rate. Extended wings are superior for slow glides and turns; swept wings are superior for fast glides and turns. This superiority is due to better aerodynamic performance—with the exception of fast turns. Swept wings are less effective at generating lift while turning at high speeds, but can bear the extreme loads. Finally, our glide model predicts that cost-effective gliding occurs at speeds of 8–10 m s-1, whereas agility-related figures of merit peak at 15–25 m s-1. In fact, swifts spend the night (‘roost’) in flight at 8–10 m s-1 (ref. 11), thus our model can explain this choice for a resting behaviour. Morphing not only adjusts birds’ wing performance to the task at hand, but could also control the flight of future aircraft.

Nature

2995049

10.1242/JEB.00680

Hot bees in empty broodnest cells: heating from within

SUMMARY Honeybee colonies maintain brood nest temperatures of 33–36°C. We investigated brood nest thermoregulation at the level of individual worker behaviour and the transfer of heat from workers to the brood. Worker bees contribute to the regulation of brood nest temperature by producing heat while sitting motionless on the caps of brood cells. We report here an additional, newly observed heating strategy where heating bees enter empty cells between sealed brood cells and remain there motionless for periods of up to 45 min. Individually marked worker bees on the surface of sealed brood cells maintained thorax temperatures (Tth) between 32.2±1.0°C and 38.1±2.5°C (mean ± s.d.; N=20 bees) with alternating warming and cooling periods. Most of the observed bees made one or several long-duration visits (>2 min) to empty cells within the sealed brood area. Tth at the time bees entered a cell [Tth(entry)] was 34.1–42.5°C (N=40). In 83% of these cell visits, Tth(entry) was higher (up to 5.9°C; mean 2.5±1.5°C; N=33) than the mean Tth of the same bee. High values of Tth(entry) resulted from preceding heating activity on the comb surface and from warm-ups just prior to cell visits during which Tth increased by up to +9.6°C. Bees inside empty cells had mean Tth values of 32.7±0.1°C (resting bees) to 40.6±0.7°C (heat-producing bees) during long-duration cell visits without performing any visible work. Heating behaviour inside cells resembles heating behaviour on the brood cap surface in that the bees appear to be inactive, but repeated warmings and coolings occur and Tth does not fall below the optimum brood temperature. Bees staying still inside empty cells for several minutes have previously been considered to be `resting bees'. We find, however, that the heating bees can be distinguished from the resting bees not only by their higher body temperatures but also by the continuous, rapid respiratory movements of their abdomens. By contrast, abdominal pumping movements in resting bees are discontinuous and interrupted by long pauses. Heat transfer to the brood from individual bees on the comb surface and from bees inside empty cells was simulated under controlled conditions. Heating on the comb surface causes a strong superficial warming of the brood cap by up to 3°C within 30 min. Heat transfer is 1.9–2.6 times more efficient when the thorax is in touch with the brood cap than when it is not. Heating inside empty cells raises the brood temperature of adjacent cells by up to 2.5°C within 30 min. Heat flow through the comb was detectable up to three brood cells away from the heated thorax.

The Journal of Experimental Biology

16670564

10.1073/PNAS.1018740108

Bat wing sensors support flight control

Bats are the only mammals capable of powered flight, and they perform impressive aerial maneuvers like tight turns, hovering, and perching upside down. The bat wing contains five digits, and its specialized membrane is covered with stiff, microscopically small, domed hairs. We provide here unique empirical evidence that the tactile receptors associated with these hairs are involved in sensorimotor flight control by providing aerodynamic feedback. We found that neurons in bat primary somatosensory cortex respond with directional sensitivity to stimulation of the wing hairs with low-speed airflow. Wing hairs mostly preferred reversed airflow, which occurs under flight conditions when the airflow separates and vortices form. This finding suggests that the hairs act as an array of sensors to monitor flight speed and/or airflow conditions that indicate stall. Depilation of different functional regions of the bats’ wing membrane altered the flight behavior in obstacle avoidance tasks by reducing aerial maneuverability, as indicated by decreased turning angles and increased flight speed.

Proceedings of the National Academy of Sciences of the United States of America

207169569

10.1242/JEB.051581

Cross-linking by protein oxidation in the rapidly setting gel-based glues of slugs

SUMMARY The terrestrial slug Arion subfuscus secretes a glue that is a dilute gel with remarkable adhesive and cohesive strength. The function of this glue depends on metals, raising the possibility that metal-catalyzed oxidation plays a role. The extent and time course of protein oxidation was measured by immunoblotting to detect the resulting carbonyl groups. Several proteins, particularly one with a relative molecular mass (Mr) of 165×103, were heavily oxidized. Of the proteins known to distinguish the glue from non-adhesive mucus, only specific size variants were oxidized. The oxidation appears to occur within the first few seconds of secretion. Although carbonyls were detected by 2,4-dinitrophenylhydrazine (DNPH) in denatured proteins, they were not easily detected in the native state. The presence of reversible cross-links derived from carbonyls was tested for by treatment with sodium borohydride, which would reduce uncross-linked carbonyls to alcohols, but stabilize imine bonds formed by carbonyls and thus lead to less soluble complexes. Consistent with imine bond formation, sodium borohydride led to a 20–35% decrease in the amount of soluble protein with a Mr of 40–165 (×103) without changing the carbonyl content per protein. In contrast, the nucleophile hydroxylamine, which would competitively disrupt imine bonds, increased protein solubility in the glue. Finally, the primary amine groups on a protein with a Mr of 15×103 were not accessible to acid anhydrides. The results suggest that cross-links between aldehydes and primary amines contribute to the cohesive strength of the glue.

The Journal of Experimental Biology

87189397

10.1086/PHYSZOOL.56.2.30156051

Blood Flow to Appendages and the Control of Heat Exchange in American Alligators

Small American alligators (200-400 g) were heated and cooled from 20 to 35 to 20 C in a temperature-controlled wind tunnel. Blood flow to the limbs and tail was periodically occluded, using remotely controlled occlusion cuffs. When blood flow in all appendages was occluded, the rate of heating was significantly reduced from that when blood flow was unrestricted. The rate of cooling was not significantly affected by occlusion of blood flow in all appendages, however. Blood flow to appendages, rather than a generalized perfusion of the skin, appears to be primarily responsible for the differences in the rates of heating and cooling in alligators.

Physiological and Biochemical Zoology

84994874

10.1016/J.FLORA.2010.01.006

Desert geophytes under dew and fog: The “curly-whirlies” of Namaqualand (South Africa)

Abstract In the semidesert of Namaqualand and adjacent regions of the former Cape Province, South Africa, there occurs an assemblage of geophytes belonging to eight monocot families and some Oxalis species that exhibit special morphological adaptations of their aerial parts to harvest and absorb water from dew and fog, the main source of moisture in this region. Most of them pass their vegetative phase in winter. Leaves and in some cases axes, display a circinate, helical, tortuose, or serpentine shape and/or their margins are undulate or crispate, or (and) are provided with a ciliate or fimbriate pilosity of uncommon appearance. These morphomes, rare elsewhere among monocotyledons, promote an increased deposit of dew and fog by enlargement of surfaces and edges, keeping at the same time the overall size of the leaves restricted. They improve the water budget of these plants in three ways: (1) remnant water on the aerial parts retards the transpiration stress at day-time; (2) although special organs for direct absorption seem to be absent, field and laboratory tests show, that considerable uptake of water occurs but in quantities not exceeding that capacity found in many non-desert plants; (3) the water harvest of the leaves dripping to the soil and reaching the root zone, where it is stored in tubers, bulbs, corms and rhizomes, appears to be the main contribution. Experiments using artificial, directional fog and metal models imitating the natural profiles demonstrate that a surplus of water in efficiency rates of 0.1–66% is collected by the various surface types compared to a standard model with a non-sculptured (plain) frontal surface of the same size. The higher rates are sufficient to moisten the underlying soil down to the rhizosphere. The circumference of roots and storage organs probably does not exceed the area shadowed by the foliage. Namaqualand geophytes with such morphologies apparently form a novel desert biotype: as mesophytes they represent a distinguished strategy besides that of succulents and other xerophytes.

Flora

23282128

10.1016/J.ZOOL.2011.03.002

Biomechanics on the half shell: functional performance influences patterns of morphological variation in the emydid turtle carapace.

This study uses the carapace of emydid turtles to address hypothesized differences between terrestrial and aquatic species. Geometric morphometrics are used to quantify shell shape, and performance is estimated for two shell functions: shell strength and hydrodynamics. Aquatic turtle shells differ in shape from terrestrial turtle shells and are characterized by lower frontal areas and presumably lower drag. Terrestrial turtle shells are stronger than those of aquatic turtles; many-to-one mapping of morphology to function does not entirely mitigate a functional trade-off between mechanical strength and hydrodynamic performance. Furthermore, areas of morphospace characterized by exceptionally poor performance in either of the functions are not occupied by any emydid species. Though aquatic and terrestrial species show no significant differences in the rate of morphological evolution, aquatic species show a higher lineage density, indicative of a greater amount of convergence in their evolutionary history. The techniques employed in this study, including the modeling of theoretical shapes to assess performance in unoccupied areas of morphospace, suggest a framework for future studies of morphological variation.

Zoology

93792501

10.1016/S0927-0248(02)00412-9

New materials for solar thermal storage—solid/liquid transitions in fatty acid esters

Abstract Solid/liquid transitions were studied by DSC measurements in the following fatty acid esters: methyl stearate, methyl palmitate, cetyl stearate, cetyl palmitate and their binary mixtures. Four systems, with phase transition temperature close to room temperature and with high enthalpy of transition and low hysteresis, were selected for further studies relevant to passive solar thermal storage. The selected systems were: methyl palmitate and the eutectic mixtures of methyl stearate–methyl palmitate, methyl stearte–cetyl palmitate and methyl stearate–cetyl stearate. The samples, studied in 50 thermal cycles with programmed heating/cooling in the temperature range −10–60°C remained stable. The studies of the samples, having been stored at room temperature, were repeated after an interval of 18 months. The results showed that the relevant thermophysical properties did not change. The commercial building materials (gypsum, bricks) were impregnated homogeneously with the selected molten esters by simple immersion. DSC studies showed that up to ≈30 mass% of esters can be adsorbed in the building materials. The thermal energy available for storage as latent heat of melting amounts to 60 kJ/kg of the composite material.

Solar Energy Materials and Solar Cells

23751560

10.1111/J.1469-8137.2005.01618.X

Baobab trees (Adansonia) in Madagascar use stored water to flush new leaves but not to support stomatal opening before the rainy season.

Baobab trees (Adansonia, Bombacaceae) are widely thought to store water in their stems for use when water availability is low. We tested this hypothesis by assessing the role of stored water during the dry season in three baobab species in Madagascar. In the dry season, leaves are present only during and after leaf flush. We quantified the relative contributions of stem and soil water during this period through measures of stem water content, sap flow and stomatal conductance. Rates of sap flow at the base of the trunk were near zero, indicating that leaf flushing was almost entirely dependent on stem water. Stem water content declined by up to 12% during this period, yet stomatal conductance and branch sap flow rates remained very low. Stem water reserves were used to support new leaf growth and cuticular transpiration, but not to support stomatal opening before the rainy season. Stomatal opening coincided with the onset of sap flow at the base of the trunk and occurred only after significant rainfall.

New Phytologist

2903109

10.1111/J.1469-8137.2009.02854.X

Leaves in the lowest and highest winds: temperature, force and shape.

Climatic extremes can be as significant as averages in setting the conditions for successful organismal function and in determining the distribution of different forms. For lightweight, flexible structures such as leaves, even extremes lasting a few seconds can matter. The present review considers two extreme situations that may pose existential risks. Broad leaves heat rapidly when ambient air flows drop below c. 0.5 m s(-1). Devices implicated in minimizing heating include: reduction in size, lobing, and adjustments of orientation to improve convective cooling; low near-infrared absorptivity; and thickening for short-term heat storage. Different features become relevant when storm gusts threaten to tear leaves and uproot trees with leaf-level winds of 20 m s(-1) or more. Both individual leaves and clusters may curl into low-drag, stable cones and cylinders, facilitated by particular blade shapes, petioles that twist readily, and sufficient low-speed instability to initiate reconfiguration. While such factors may have implications in many areas, remarkably little relevant experimental work has addressed them.

New Phytologist

1591399

10.1644/08-MAMM-A-108.1

Home Ranges, Movement, and Den Use in Long-Beaked Echidnas, Zaglossus Bartoni, from Papua New Guinea

Abstract Long-beaked echidnas (Zaglossus), which are endemic to New Guinea, are the largest and least-studied of the 3 extant genera of monotremes. Zaglossus is listed as endangered by the World Conservation Union and data regarding the natural history of long-beaked echidnas are critical to efforts to protect these animals. However, no detailed studies of the ecology of this genus have been published. From 2000 to 2005, I captured 22 Zaglossus bartoni in the Crater Mountain Wildlife Management Area in Simbu Province, Papua New Guinea. Mean body masses for these animals were 6.5 kg ± 1.4 SD (n = 15, range: 4.2–9.1 kg) for adults and 4.3 ± 7.4 kg (n = 6, range: 3.2–5.1 kg) for juveniles. Eleven of the adults captured were followed via radiotelemetry for 1–12 months. The home ranges for these individuals varied in size from 10 to 168 ha. Home-range size was not correlated with body mass, age, or sex. Long-beaked echidna dens were most commonly located in underground burrows, although individual echidnas favored different types of den sites. Mean burrow length was 2.7 m ± 1.8 SD (n = 5, range: 1.3–4.9 m) and mean den depth was 0.48 m ± 7.8 SD (n = 5, range: 0.42–0.57 m) below the soil surface. Animals were never found foraging in daylight. Although no animals were found with eggs or young in the pouch, 1 individual was lactating when captured in April 2002 and again in April 2005. The data generated by this study provide valuable insights into echidna biology that will facilitate efforts to conserve populations of these unusual mammals.

Journal of Mammalogy

1266462

10.1016/J.CUB.2007.07.002

Microtubule Polymerization: One Step at a Time

The dynamic assembly of microtubules is a key factor in many of their functions in the cell and recent experiments give new insight into this process at the molecular level.

Current Biology

83896675

10.1126/SCIENCE.290.5500.2231A

Fighting Bacterial Fire With Bacterial Fire

MICROBIOLOGYWork presented last week at the annual meeting of the American Society for Cell Biology in San Francisco suggests that applying a harmless bacterium or its products to surgical wounds may thwart infections by the dangerous pathogen Staphylococcus aureus , a major cause of hospital-acquired infections. Although physicians have previously pitted one bacterium against another to prevent infections of the intestinal and genitourinary tracts, this is the first attempt to use a friendly microbe to prevent infection of surgical wounds, say experts. The findings also point to a possible mechanism for this "bacterial interference." They suggest that a protein secreted by the harmless bacterium prevents the pathogen from getting a foothold in injured tissue.

Science

664040

10.1098/RSPB.2011.2238

Morphological and kinematic basis of the hummingbird flight stroke: scaling of flight muscle transmission ratio

Hummingbirds (Trochilidae) are widely known for their insect-like flight strokes characterized by high wing beat frequency, small muscle strains and a highly supinated wing orientation during upstroke that allows for lift production in both halves of the stroke cycle. Here, we show that hummingbirds achieve these functional traits within the limits imposed by a vertebrate endoskeleton and muscle physiology by accentuating a wing inversion mechanism found in other birds and using long-axis rotational movement of the humerus. In hummingbirds, long-axis rotation of the humerus creates additional wing translational movement, supplementing that produced by the humeral elevation and depression movements of a typical avian flight stroke. This adaptation increases the wing-to-muscle-transmission ratio, and is emblematic of a widespread scaling trend among flying animals whereby wing-to-muscle-transmission ratio varies inversely with mass, allowing animals of vastly different sizes to accommodate aerodynamic, biomechanical and physiological constraints on muscle-powered flapping flight.

Proceedings of The Royal Society B: Biological Sciences

10096941

10.1016/J.TOXICON.2009.03.006

Cnidocyst structure and the biomechanics of discharge.

The cnidocyst is the defining organelle of the cnidarians, used for capture of prey and defense. It consists of a cylindrical capsule, which releases a long tubule upon triggering. Cnidocysts develop inside a giant post-Golgi vesicle by a sequential accumulation of proteins from the Golgi apparatus. Traditionally three types of cnidocysts are distinguished: nematocysts, spirocysts, and ptychocysts. Here we focus on nematocysts, the prototypic cnidocyst and by far most diverse group of cnidocysts in this phylum. The mature nematocyst capsule comprises a collagenous polymer with remarkable biophysical properties, able to withstand an osmotic pressure of 150 bar. Release of the capsule and discharge is probably initiated by classical exocytosis. High-speed studies revealed the kinetics of discharge to be as short as 700 ns, generating an acceleration of 5,400,000 x g and a pressure of 7.7 GPa at the site of impact of the spines onto the prey. Thus nematocysts comprise a powerful molecular spring mechanism releasing energy stored in the wall polymer in the nanosecond time range. During the last few years, genomic, biochemical and structural studies have helped to unravel the molecular composition of the nematocyst supra-structure. Here we summarize these findings and present an integrative view of mechanical and molecular aspects that have shaped the nematocyst during evolution.

Toxicon

84611191

10.1139/B72-179

Abscission and dehiscence in the squirting cucumber, Ecballium elaterium. Regulation by ethylene

When treated with ethylene, mature fruits of the squirting cucumber (Ecballium elaterium (L.) A. Rich) abscind and dehisce prematurely. Abscission of male flowers is also accelerated by ethylene. Visible signs of senescence, a rise in ethylene production, and reduced carbon dioxide production always precede abscission or dehiscence in untreated fruits and flowers. The amounts of diffusible cellulase increase in tissues on both sides of the fruit abscission zone after exposure to ethylene. Anatomical features of this abscission zone are described.The leaves of Ecballium do not abscind although the blade and petiole produce large amounts of ethylene at senescence, nor do they separate when ethylene is supplied. Ethylene treatment of attached fruit peduncles accelerates their rate of elongation in the growing zone below the apical hook. The regulation of growth and abscission in these organs is discussed.

Botany

1179814

10.1098/RSIF.2011.0059

The effect of individual variation on the structure and function of interaction networks in harvester ants

Social insects exhibit coordinated behaviour without central control. Local interactions among individuals determine their behaviour and regulate the activity of the colony. Harvester ants are recruited for outside work, using networks of brief antennal contacts, in the nest chamber closest to the nest exit: the entrance chamber. Here, we combine empirical observations, image analysis and computer simulations to investigate the structure and function of the interaction network in the entrance chamber. Ant interactions were distributed heterogeneously in the chamber, with an interaction hot-spot at the entrance leading further into the nest. The distribution of the total interactions per ant followed a right-skewed distribution, indicating the presence of highly connected individuals. Numbers of ant encounters observed positively correlated with the duration of observation. Individuals varied in interaction frequency, even after accounting for the duration of observation. An ant's interaction frequency was explained by its path shape and location within the entrance chamber. Computer simulations demonstrate that variation among individuals in connectivity accelerates information flow to an extent equivalent to an increase in the total number of interactions. Individual variation in connectivity, arising from variation among ants in location and spatial behaviour, creates interaction centres, which may expedite information flow.

Journal of the Royal Society Interface

139047715

10.1080/15376490590928598

Mechanisms in Failure Prevention of Bio-Materials and Bio-Structures

Abstract Nature is replete with examples of layered-structure materials that are evolved through billions of years to provide high performance. Insect elytra (a portion of the exoskeleton) have evoked worldwide research attention and are believed to serve as fuselages and wings of natural aircraft. This work focuses on the relationship between structure, mechanical behavior, and failure mechanisms of the elytra. We report a failure-mode-optimization (FMO) mechanism that can explain elytra's mechanical behaviors. We show initial evidence that this mechanism makes bio-structures of low-strength materials strong and ductile that can effectively resist shear forces and crack growth. A bio-inspired design of a joint by using the FMO mechanism has been proved by experiments to have a potential to increase the interface shear strength as high as about 2.5 times. The FMO mechanism, which is based on the new concept of property-structure synergetic coupling proposed in this work, offer some thoughts to deal with the notoriously difficult problem of interface strength and to reduce catastrophic failure events.

Mechanics of Advanced Materials and Structures

7419692

10.1038/NMAT858

Molecular nanosprings in spider capture-silk threads

Spider capture silk is a natural material that outperforms almost any synthetic material in its combination of strength and elasticity. The structure of this remarkable material is still largely unknown, because spider-silk proteins have not been crystallized. Capture silk is the sticky spiral in the webs of orb-weaving spiders. Here we are investigating specifically the capture spiral threads from Araneus, an ecribellate orb-weaving spider. The major protein of these threads is flagelliform protein, a variety of silk fibroin. We present models for molecular and supramolecular structures of flagelliform protein, derived from amino acid sequences, force spectroscopy (molecular pulling) and stretching of bulk capture web. Pulling on molecules in capture-silk fibres from Araneus has revealed rupture peaks due to sacrificial bonds, characteristic of other self-healing biomaterials. The overall force changes are exponential for both capture-silk molecules and intact strands of capture silk.

Nature Materials

17074649

10.1242/JEB.01892

Comparative overwintering physiology of Alaska and Indiana populations of the beetle Cucujus clavipes (Fabricius): roles of antifreeze proteins, polyols, dehydration and diapause

SUMMARY The beetle Cucujus clavipes is found in North America over a broad latitudinal range from North Carolina (latitude ∼35°N) to near tree line in the Brooks Range in Alaska (latitude, ∼67°30′ N). The cold adaptations of populations from northern Indiana (∼41°45′ N) and Alaska were compared and, as expected, the supercooling points (the temperatures at which they froze) of these freeze-avoiding insects were significantly lower in Alaska insects. Both populations produce glycerol, but the concentrations in Alaska larvae were much higher than in Indiana insects (∼2.2 and 0.5 mol l–1, respectively). In addition, both populations produce antifreeze proteins. Interestingly, in the autumn both populations have the same approximate level of hemolymph thermal hysteresis, indicative of antifreeze protein activity, suggesting that they synthesize similar amounts of antifreeze protein. A major difference is that the Alaska larvae undergo extreme dehydration in winter wherein water content decreases from 63–65% body water (1.70–1.85 g H2O g–1 dry mass) in summer to 28–40% body water (0.40–0.68 g H2O g–1 dry mass) in winter. These 2.5–4.6-fold reductions in body water greatly increase the concentrations of antifreeze in the Alaska insects. Glycerol concentrations would increase to 7–10 mol l–1 while thermal hysteresis increased to nearly 13°C (the highest ever measured in any organism) in concentrated hemolymph. By contrast, Indiana larvae do not desiccate in winter. The Alaska population also undergoes a diapause while insects from Indiana do not. The result of these, and likely additional, adaptations is that while the mean winter supercooling points of Indiana larvae were approximately –23°C, those of Alaska larvae were –35 to– 42°C, and at certain times Alaska C. clavipes did not freeze when cooled to –80°C.

The Journal of Experimental Biology

120772884

10.1088/1367-2630/10/3/033014

Diffractive hygrochromic effect in the cuticle of the hercules beetle Dynastes hercules

The elytra from dry specimens of the hercules beetle, Dynastes hercules appear khaki-green in a dry atmosphere and turn black passively under high humidity levels. New scanning electron images, spectrophotometric measurements and physical modelling are used to unveil the mechanism of this colouration switch. The visible dry-state greenish colouration originates from a widely open porous layer located 3 μm below the cuticle surface. The structure of this layer is three-dimensional, with a network of filamentary strings, arranged in layers parallel to the cuticle surface and stiffening an array of strong cylindrical pillars oriented normal to the surface. Unexpectedly, diffraction plays a significant role in the broadband colouration of the cuticle in the dry state. The backscattering caused by this layer disappears when water infiltrates the structure and weakens the refractive index differences.

New Journal of Physics

45267885

10.1016/J.TPLANTS.2006.07.002

Gamma-aminobutyrate: defense against invertebrate pests?

Gamma-aminobutyrate (GABA) is a ubiquitous four-carbon, non-protein amino acid. In plants, stress-induced GABA accumulation is well documented. However, the role(s) of GABA accumulation is contentious. In this Opinion article, we argue that wounding due to herbivory and crawling by insect larvae causes rapid GABA accumulation via the disruption of cellular compartmentation and the release of the acidic vacuolar contents to the cytosol. The activity of glutamate decarboxylase, the cytosolic enzyme responsible for GABA synthesis, has an acidic pH optimum. Subsequent GABA ingestion has a plant defense function by directly acting on GABA-regulated invertebrate neuromuscular junctions. Plants with an enhanced GABA-producing capacity reduce herbivory by invertebrate pests. These findings suggest that GABA accumulation is a rapidly deployed, local resistance mechanism that constitutes a first line of defense in deterring herbivory.

Trends in Plant Science

84073865

10.1139/B80-193

Light transmission in window-leaved plants

Window-leaved plants are succulent plants which possess areas of clear epidermis on their leaves. The underlying water storage tissue is transparent to allow light penetration to the internal chlorenchyma. The most highly evolved window-leaved plants with the most transparent tissue grow completely underground in desert regions. Only the rounded leaf tips are level with the soil surface and directly exposed to incident light. Light transmission curves were measured using live windows of five species of plants from three families (Liliaceae, Piperaceae, Mesembryanthemaceae). These results suggest that subterranean window leaves may be limited to a relatively short effective maximum length because of light absorption by the tissues involved. Scanning electron micrographs (SEM) of these plants show considerable differences in surface structure which may help to modulate incident light. Comparisons with related Mesembryanthemaceae illustrate that a complex series of adaptations have been developed to allow un...

Botany

12975364

10.1086/340126

Lactobacillus fermentum RC-14 inhibits Staphylococcus aureus infection of surgical implants in rats.

Staphylococcus aureus is a common cause of community and hospital-acquired infections. Moreover, the clinical impact of S. aureus is on the rise because of the global increase in the incidence of multidrug-resistant strains and its growing prevalence as a major cause of surgical infections. As a result, there is a pressing need to identify new antistaphylococcal agents and preventative strategies that will help in the management of these types of infections. This report describes the successful use of a probiotic, Lactobacillus fermentum RC-14, and its secreted biosurfactant to inhibit surgical implant infections caused by S. aureus. L. fermentum RC-14 and its secreted biosurfactant both significantly inhibited S. aureus infection and bacteria adherence to surgical implants.

The Journal of Infectious Diseases

7850333

10.2307/1368982

A test of whether economy or nutrition determines fecal sac ingestion in nesting corvids

Parent birds of many species eat the fecal sacs produced by their nestlings. Two hypotheses have been proposed to explain why the parents ingest, rather than simply remove the sacs. (1) The parental nutrition hypothesis proposes that the parent benefits energetically or nutritionally from ingesting the sacs (Morton 1979, Gluck 1988); and (2) the economic disposal hypothesis postulates that parents incur some costs from eating waste products, but the cost of eating them is less than the benefits gained from being allowed to remain at the nest (Hurd et al. 1991). Behavioral data on nesting Florida Scrub Jays (Aphelocoma c. coerulescens) and American Crows (Corvus brachyrhynchos) support the parental nutrition, and not the economic disposal hypothesis. In both species, when two parents were present at the production of fecal sacs, the most nutritionally stressed parent, the female, ate significantly more sacs than her mate. On occasions where one adult left the nest immediately after fecal sac production and one remained, the departing adult was not more likely to dispose of the sac in either species. In neither species was a departing adult more likely to carry of a fecal sac than eat it

The Condor

86252465

10.1111/J.1469-8137.1978.TB02285.X

THE ANT‐PLANTS MYRMECODIA AND HYDNOPHYTUM (RUBIACEAE), AND THE RELATIONSHIPS BETWEEN THEIR MORPHOLOGY, ANT OCCUPANTS, PHYSIOLOGY AND ECOLOGY

SUMMARY The history of investigation of the ant-plants is briefly reviewed and the external morphology of the plants described. Within Papua New Guinea ant-plants are abundant in open-canopied environments and less common but more diverse in rain forest. They also occur terrestrially above 2400 m. Initial tuber development was found to be similar that described by Treub (1883). Later cavities are formed by successive, increasingly complex phellogens. In certain Myrmecodia spp. later cavities are differentiated into regions with distinct surface characteristics, shapes and positions. Cavities in Hydnophytum are simpler in shape but sometimes differentiated in other ways. The anatomy of the cavity surfaces, especially the putative absorption sites ('warts') is described. The ant Iridomyrmex cordatus, which is common in ant-plants in other regions, is found in ant-plants in open habitats in Papua New Guinea, but is replaced by I. cf. scrutator in rain forest and above 2000 m. Two fungi, known also from ant-plants in Java (Miehe, 1911a), occur in the cavities of ant-plants throughout Papua New Guinea. Arthrocladium sp. Papend. grows on cavity surfaces where ant faecal material is present and the other (an unidentified Monilialine fungus) is parasitic on smooth, clean surfaces. The former is most common and the latter almost confined to Myrmecodia spp. occupied by Iridomyrmex cordatus. Experiments suggested that both Hydnophytum under artificial conditions and Myrmecodia under field conditions grow better in the presence than absence of Iridomyrmex cordatus and that the stimulus might be that of minerals supplied by the ants. Radioisotopes in both organic and inorganic compounds fed to I. cordatus were deposited preferentially by the ants on the warted cavity surfaces where ant faecal material was present, and were absorbed by the plants. In the discussion it is argued that the plant/ant relationship has had a considerable influence on both the ecology and evolution of the plants, but that this varies in different species.

New Phytologist

85425546

10.1017/S0266467498000364

The mound-building termite Macrotermes michaelseni as an ecosystem engineer

Many organisms create or alter resource flows that affect the com- position and spatial arrangement of current and future organismal diversity. The phenomenon called ecosystem engineering is considered with a case study of the mound building termite Macrotermes michaelseni. It is argued that this species acts as an ecosystem engineer across a range of spatial scales, from alteration of local infiltration rates to the creation of landscape mosaics, and that its impacts accrue because of the initiation of biophysical processes that often include feedback mech- anisms. These changes to resource flows are likely to persist for long periods and constrain the biological structure of the habitat. The value of ecosystem engineer- ing is discussed as a holistic way of understanding the complexity of tropical ecology.

Journal of Tropical Ecology

84672914

10.1046/J.1461-0248.2001.00218.X

The exploitation of mutualisms

Mutualisms (interspecific cooperative interactions) are ubiquitously exploited by organisms that obtain the benefits mutualists offer, while delivering no benefits in return. The natural history of these exploiters is well-described, but relatively little effort has yet been devoted to analysing their ecological or evolutionary significance for mutualism. Exploitation is not a unitary phenomenon, but a set of loosely related phenomena: exploiters may follow mixed strategies or pure strategies at either the species or individual level, may or may not be derived from mutualists, and may or may not inflict significant costs on mutualisms. The evolutionary implications of these different forms of exploitation, especially the threats they pose to the stability of mutualism, have as yet been minimally explored. Studies of this issue are usually framed in terms of a “temptation to defect” that generates a destabilizing conflict of interest between partners. I argue that this idea is in fact rather inappropriate for interpreting most observed forms of exploitation in mutualisms. I suggest several alternative and testable ideas for how mutualism can persist in the face of exploitation.

Ecology Letters

1637480

10.1242/JEB.02063

Respiration by buried echidnas Tachyglossus aculeatus

SUMMARY Short-beaked echidnas have an impressive ability to submerge completely into soil or sand and remain there, cryptic, for long periods. This poses questions about how they manage their respiration, cut off from a free flow of gases. We measured the gradient in oxygen partial pressure (PO2) away from the snouts of buried echidnas and oxygen consumption (V̇O2) in five individuals under similar conditions, in two substrates with different air-filled porosities (fa). A theoretical diffusion model indicated that diffusion alone was insufficient to account for the flux of oxygen required to meet measured rates of V̇O2. However, it was noticed that echidnas often showed periodic movements of the anterior part of the body, as if such movements were a deliberate effort to flush the tidal air space surrounding their nostrils. These `flushing movements' were subsequently found to temporarily increase the levels of interstitial oxygen in the soil around the head region. Flushing movements were more frequent while V̇O2 was higher during the burrowing process, and also in substrate with lower fa. We conclude that oxygen supply to buried echidnas is maintained by diffusion through the soil augmented by periodic flushing movements, which ventilate the tidal airspace that surrounds the nostrils.

The Journal of Experimental Biology

53186365

10.1006/ANBE.1994.1088

Bill sweeping in the spoonbill, Platalea leucordia: evidence for a hydrodynamic function

Abstract Abstract. Spoonbills (Aves: Platalea spp., Ciconiiformes) characteristically feed by wading in shallow water and rhythmically sweeping their submerged and partially opened bills in an arc. This bill sweeping contrasts with the direct grasp, strike or stab employed by related species (storks, Ciconiidae; herons, Ardeidae) for similar prey (crustaceans, fish). A related feature of spoonbills is the shape of the bill: both upper and lower mandibles are dorso-ventrally flattened, the upper mandible being convex in cross section while the lower is tucked in, to result in an almost flat surface. The bill is wide throughout and broadens at the distal end. The hypothesis presented here is that spoonbills use their broad, flattened bills and lateral sweeping to shed a vortex off the tip of the bill that results in hydrodynamic suction on the bottom, which disturbs and moves prey. To achieve this the bill is used as a hydrofoil. The analysis predicts, and experimental results show that (1) in feeding, the tip of the bill is kept close to the bottom, (2) there is an inverse relationship between bill immersion depth and sweeping speed, and (3) bill sweeping over submerged prey results in the prey being lifted into the water column. This is the first reported case of an avian bill being used as a hydrofoil.

Animal Behaviour

25397253

10.1086/651593

Differential Response to Circularly Polarized Light by the Jewel Scarab Beetle Chrysina gloriosa

Circularly polarized light is rare in the terrestrial environment, and cuticular reflections from scarab beetles are one of the few natural sources. Chrysina gloriosa LeConte 1854, a scarab beetle found in montane juniper forests of the extreme southwestern United States and northern Mexico, are camouflaged in juniper foliage; however, when viewed with right circularly polarizing filters, the beetles exhibit a stark black contrast. Given the polarization‐specific changes in the appearance of C. gloriosa, we hypothesized that C. gloriosa can detect circularly polarized light. We tested for phototactic response and differential flight orientation of C. gloriosa toward different light stimuli. Chrysina gloriosa exhibited (a) positive phototaxis, (b) differential flight orientation between linear and circularly polarized light stimuli of equal intensities, and (c) discrimination between circularly polarized and unpolarized lights of different intensities consistent with a model of circular polarization sensitivity based on a quarter‐wave plate. These results demonstrate that C. gloriosa beetles respond differentially to circularly polarized light. In contrast, Chrysina woodi Horn 1885, a close relative with reduced circularly polarized reflection, exhibited no phototactic discrimination between linear and circularly polarized light. Circularly polarized sensitivity may allow C. gloriosa to perceive and communicate with conspecifics that remain cryptic to predators, reducing indirect costs of communication.

The American Naturalist

137681245

10.1007/BF03399488

Locomotion of Gymnarchus niloticus : Experiment and kinematics

In addition to forward undulatory swimming, Gymnarchus niloticus can swim via undulations of the dorsal fin while the body axis remains straight; furthermore, it swims forward and backward in a similar way, which indicates that the undulation of the dorsal fin can simultaneously provide bidirectional propulsive and maneuvering forces with the help of the tail fin. A high-resolution Charge-Coupled Device (CCD) imaging camera system is used to record kinematics of steady swimming as well as maneuvering in G. niloticus. Based on experimental data, this paper discusses the kinematics (cruising speed, wave speed, cycle frequency, amplitude, lateral displacement) of forward as well as backward swimming and maneuvering.During forward swimming, the propulsive force is generated mainly by undulations of the dorsal fin while the body axis remains straight. The kinematic parameters (wave speed, wavelength, cycle frequency, amplitude) have statistically significant correlations with cruising speed. In addition, the yaw at the head is minimal during steady swimming. From experimental data, the maximal lateral displacement of head is not more than 1% of the body length, while the maximal lateral displacement of the whole body is not more than 5% of the body length. Another important feature is that G. niloticus swims backwards using an undulatory mechanism that resembles the forward undulatory swimming mechanism. In backward swimming, the increase of lateral displacement of the head is comparatively significant; the amplitude profiles of the propulsive wave along the dorsal fin are significantly different from those in forward swimming. When G. niloticus does fast maneuvering, its body is first bent into either a C shape or an S shape, then it is rapidly unwound in a travelling wave fashion. It rarely maneuvers without the help of the tail fin and body bending.

Journal of Bionic Engineering

6709383

10.1088/1748-3182/2/4/S01

Insects did it first: a micropatterned adhesive tape for robotic applications.

Based on the structural and experimental studies of more than 300 insect species from different lineages, we have developed and characterized a bioinspired polymer material with the ability of multiple glue-free bonding and debonding. The material surface is covered with a pattern of microstructures, which resembles the geometry of tenent hairs previously described from the feet of flies, beetles, earwigs and other insects. The tape with such a microstructure pattern demonstrates at least two times higher pull-off force per unit apparent contact area compared to the flat polymer. Additionally, the tape is less sensitive to contamination by dust particles than a commercially available pressure-sensitive adhesive tape. Even if the 'insect tape' is contaminated, it can be washed with a soap solution in water, in order to completely recover its adhesive properties. We have successfully applied the tape to the 120 g wall-climbing robot Mini-Whegs. Furthermore, the tape can be used for multiple adhering of objects to glass surfaces or as a protective tape for sensitive glass surfaces of optical quality. Another area of potential applications is gripping and manipulation of objects with smooth surfaces.

Bioinspiration & Biomimetics

4333455

10.1038/325146A0

Antifreeze activity of Antarctic fish glycoprotein and a synthetic polymer

Antifreeze glycoproteins (AFGPs) and proteins isolated from the sera of some polar fish species and overwintering insects are able to depress the freezing temperature of the aqueous body fluids (and of water) by means of a non-col ligative mechanism1,2. All previous measurements of the antifreeze effect have been performed on bulk samples under conditions where ice nucleation would be catalysed by participate impurities, giving limited and indeterminate degrees of undercooling. We report the first measurements of homogeneous (spontaneous) ice nucleation rates in deeply under-cooled (<233 K) solutions of AFGP and polyvinyl pyrrolidone (PVP), a well-characterized polymer which finds use as a cryoprotectant. Antifreeze activity is said3 to derive from the sorption of AFGP molecules on the active growth sites of ice crystals, preventing normal growth and inducing unusual crystal habits. We have performed experiments on the inhibition of ice crystal growth in solutions containing AFGP and PVP under standardized conditions, and find that the homogeneous nucleation and crystallization rates are sensitive to low concentrations of both substances, but AFGP is remarkably effective at inhibiting ice crystal growth.

Nature

947293

10.1159/000328223

Are Wet-Induced Wrinkled Fingers Primate Rain Treads?

Wet fingers and toes eventually wrinkle, and this is commonly attributed by lay opinion to local osmotic reactions. However, nearly a century ago surgeons observed that no wrinkling occurs if a nerve to the finger has been cut. Here we provide evidence that, rather than being an accidental side effect of wetness, wet-induced wrinkles have been selected to enhance grip in wet conditions. We show that their morphology has the signature properties of drainage networks, enabling efficient removal of water from the gripped surface.

Brain Behavior and Evolution

6421401

10.1098/RSTA.2010.0201

Shark-skin surfaces for fluid-drag reduction in turbulent flow: a review

The skin of fast-swimming sharks exhibits riblet structures aligned in the direction of flow that are known to reduce skin friction drag in the turbulent-flow regime. Structures have been fabricated for study and application that replicate and improve upon the natural shape of the shark-skin riblets, providing a maximum drag reduction of nearly 10 per cent. Mechanisms of fluid drag in turbulent flow and riblet-drag reduction theories from experiment and simulation are discussed. A review of riblet-performance studies is given, and optimal riblet geometries are defined. A survey of studies experimenting with riblet-topped shark-scale replicas is also given. A method for selecting optimal riblet dimensions based on fluid-flow characteristics is detailed, and current manufacturing techniques are outlined. Due to the presence of small amounts of mucus on the skin of a shark, it is expected that the localized application of hydrophobic materials will alter the flow field around the riblets in some way beneficial to the goals of increased drag reduction.

Philosophical Transactions of the Royal Society A

13568710

10.1371/JOURNAL.PONE.0000675

Auditory Spatial Acuity Approximates the Resolving Power of Space-Specific Neurons

The relationship between neuronal acuity and behavioral performance was assessed in the barn owl (Tyto alba), a nocturnal raptor renowned for its ability to localize sounds and for the topographic representation of auditory space found in the midbrain. We measured discrimination of sound-source separation using a newly developed procedure involving the habituation and recovery of the pupillary dilation response. The smallest discriminable change of source location was found to be about two times finer in azimuth than in elevation. Recordings from neurons in its midbrain space map revealed that their spatial tuning, like the spatial discrimination behavior, was also better in azimuth than in elevation by a factor of about two. Because the PDR behavioral assay is mediated by the same circuitry whether discrimination is assessed in azimuth or in elevation, this difference in vertical and horizontal acuity is likely to reflect a true difference in sensory resolution, without additional confounding effects of differences in motor performance in the two dimensions. Our results, therefore, are consistent with the hypothesis that the acuity of the midbrain space map determines auditory spatial discrimination.

PLOS ONE

362375

10.1098/RSTA.2009.0003

Actuation systems in plants as prototypes for bioinspired devices

Plants have evolved a multitude of mechanisms to actuate organ movement. The osmotic influx and efflux of water in living cells can cause a rapid movement of organs in a predetermined direction. Even dead tissue can be actuated by a swelling or drying of the plant cell walls. The deformation of the organ is controlled at different levels of tissue hierarchy by geometrical constraints at the micrometre level (e.g. cell shape and size) and cell wall polymer composition at the nanoscale (e.g. cellulose fibril orientation). This paper reviews different mechanisms of organ movement in plants and highlights recent research in the field. Particular attention is paid to systems that are activated without any metabolism. The design principles of such systems may be particularly useful for a biomimetic translation into active technical composites and moving devices.

Philosophical Transactions of the Royal Society A

14346727

10.3762/BJNANO.5.8

Friction behavior of a microstructured polymer surface inspired by snake skin

Summary The aim of this study was to understand the influence of microstructures found on ventral scales of the biological model, Lampropeltis getula californiae, the California King Snake, on the friction behavior. For this purpose, we compared snake-inspired anisotropic microstructured surfaces to other microstructured surfaces with isotropic and anisotropic geometry. To exclude that the friction measurements were influenced by physico-chemical variations, all friction measurements were performed on the same epoxy polymer. For frictional measurements a microtribometer was used. Original data were processed by fast Fourier transformation (FFT) with a zero frequency related to the average friction and other peaks resulting from periodic stick-slip behavior. The data showed that the specific ventral surface ornamentation of snakes does not only reduce the frictional coefficient and generate anisotropic frictional properties, but also reduces stick-slip vibrations during sliding, which might be an adaptation to reduce wear. Based on this extensive comparative study of different microstructured polymer samples, it was experimentally demonstrated that the friction-induced stick-slip behavior does not solely depend on the frictional coefficient of the contact pair.

Beilstein Journal of Nanotechnology

46917893

10.1002/(SICI)1097-4687(199905)240:2<101::AID-JMOR2>3.0.CO;2-7

Ultrastructure of the thoracic dorso‐medial field (TDM) in the elytra‐to‐body arresting mechanism in Tenebrionid Beetles (Coleoptera: Tenebrionidae)

Beetles with flying ability lock their elytra (forewings) to the thorax or/and abdomen using complex locking devices. These structures are often supplemented with microtrichia fields of the inner surface of the elytra and adjacent parts of the pterothorax. The present study provides information about the ultrastructure of microtrichia of the dorso‐medial fields of the thorax (TDM) in tenebrionid beetles (Tribolium castaneum, Zophobas rugipes). Epidermal cells located under the TDM field contain large electron‐lucent vesicles connected to rough endoplasmic reticulum. Microtrichia and underlying cuticle of the TDM have a high density of pore channels, which are responsible for transport of an epidermal secretion onto the TDM surface. In order to show the presence of the secretion on the cuticle surface, TDM fields of air‐dried specimens were compared with those in specimens after two treatments, such as (1) dehydration in ethanol and acetone, and (2) dental‐wax‐cast technique applied to living beetles. This revealed the presence of the nonvolatile film on the intact microtrichial surface. Possible functions of this film are suggested to be (1) the increase of adhesive forces in the contact area and (2) providing soft coupling and release of two corresponding parts of the elytra‐locking device. J. Morphol. 240:101–113, 1999. © 1999 Wiley‐Liss, Inc.

Journal of Morphology

24977941

10.1093/AOB/MCJ011

Anatomical significance of the hygrochastic movement in Anastatica hierochuntica.

BACKGROUND AND AIMS Unlike the dispersal mechanisms of many desert plants, the whole dead skeleton of Anastatica hierochuntica is involved in seed dispersal and preservation. This process depends on the hygrochastic nature of the lignified conducting tissue that bends when dry and straightens under wet conditions. An anatomical interpretation of this mechanical movement was investigated. METHODS An anatomical study of the stem was conducted on the juvenile plants raised under different water treatments and on the branch-orders of adult A. hierochuntica size-classes. KEY RESULTS In the juvenile stem of A. hierochuntica, the area of cortex, conducting tissue and pith increased with water availability. However, the hydraulic conductance decreased, resulting in a better withdrawal of water in water-stressed plants. The anatomical investigation of the hygrochastic mechanism revealed an asymmetric distribution of the cortical tissues, with the conducting tissues of the stem of juvenile and adult plants being larger in the lower side. The hydraulic conductance was better in the basal and middle branch-orders than the terminal ones, permitting better conductance of water to the subsequent branch-orders. CONCLUSIONS The lignified conducting tissue of the whole stem, having a hygrochastic nature, controls the movement of the branches. The greater amount of conducting tissue associated with a higher density of wide xylem vessels was observed in the lower side of the stem as compared with the upper side. Consequently, the conducting tissue in the lower side of the stem was suggested to be more effective in the opening process of the curled dry branches through better and more rapid conductance of water. Alternatively, due to the few narrow xylem vessels in the upper side of the stem, it was likely that the conducting tissue in the upper side is more effective in the closing process by providing more rapid drying. The mechanical rise of water and the related hygrochastic efficiency were maximized in the basal and middle branch-orders that are mostly involved in the mechanical movement.

Annals of Botany

53024166

10.1242/JEB.192492

Food dissemination in ants: robustness of the trophallactic network against resource quality

ABSTRACT Insect societies are often composed of many individuals, achieving collective decisions that depend on environmental and colonial characteristics. For example, ants are able to focus their foraging effort on the most rewarding food source. While this phenomenon is well known, the link between the food source quality and the intranidal food dissemination networks and its dynamics has been neglected. Here, we analysed the global dynamics of food dissemination in Camponotus cruentatus workers, after feeding on a low (0.1 mol l−1) or on a high (1 mol l−1) sucrose concentration food source. We also analysed the trophallaxis activity at the individual level and built the complete network of trophallaxis. The results reveal that the dynamics of food dissemination and the structure of the trophallaxis network are robust and independent of the food concentration. We discuss these results in the light of recent advances in the study of efficiency in food management in ants. Summary: Ants show a robust network of food dissemination that is not dependent on the quality of the food.

The Journal of Experimental Biology

5117094

10.1002/JEZ.708

Cold-blooded snipers: thermal independence of ballistic tongue projection in the salamander Hydromantes platycephalus.

Plethodontid salamanders of the genus Hydromantes capture prey using the most extreme tongue projection among salamanders, and can shoot the tongue a distance of 80% of body length in less than 20 msec. The tongue skeleton is projected from the body via an elastic-recoil mechanism that decouples muscle contraction from tongue projection, amplifying muscle power tenfold. We tested the hypothesis that the elastic-recoil mechanism also endows tongue projection with low thermal dependence by examining the kinematics and dynamics of tongue projection in Hydromantes platycephalus over a range of body temperatures (2-24°C). We found that H. platycephalus maintained tongue-projection performance over the tested temperature range and that tongue projection showed thermal independence (Q(10) values of 0.94-1.04) of all performance parameters including projection distance, average velocity, and peak instantaneous values of velocity, acceleration, and power. Nonelastic, muscle-powered tongue retraction, in contrast, responded to temperature changes significantly differently than elastic tongue projection; performance parameters of retraction displayed thermal dependence typical of muscle-powered movement (Q(10) values of 1.63-4.97). These results reveal that the elastic-recoil mechanism liberates tongue projection from the effects of temperature on muscle contractile rates. We suggest that relative thermal independence is a general characteristic of elastic-recoil mechanisms and may promote the evolution of these mechanisms in ectothermic animals.

Journal of Experimental Zoology

39038637

10.1098/RSTA.2011.0502

Biofouling: lessons from nature

Biofouling is generally undesirable for many applications. An overview of the medical, marine and industrial fields susceptible to fouling is presented. Two types of fouling include biofouling from organism colonization and inorganic fouling from non-living particles. Nature offers many solutions to control fouling through various physical and chemical control mechanisms. Examples include low drag, low adhesion, wettability (water repellency and attraction), microtexture, grooming, sloughing, various miscellaneous behaviours and chemical secretions. A survey of nature's flora and fauna was taken in order to discover new antifouling methods that could be mimicked for engineering applications. Antifouling methods currently employed, ranging from coatings to cleaning techniques, are described. New antifouling methods will presumably incorporate a combination of physical and chemical controls.

Philosophical Transactions of the Royal Society A

11477061

10.1371/JOURNAL.PONE.0000937

A Visual Pathway Links Brain Structures Active during Magnetic Compass Orientation in Migratory Birds

The magnetic compass of migratory birds has been suggested to be light-dependent. Retinal cryptochrome-expressing neurons and a forebrain region, “Cluster N”, show high neuronal activity when night-migratory songbirds perform magnetic compass orientation. By combining neuronal tracing with behavioral experiments leading to sensory-driven gene expression of the neuronal activity marker ZENK during magnetic compass orientation, we demonstrate a functional neuronal connection between the retinal neurons and Cluster N via the visual thalamus. Thus, the two areas of the central nervous system being most active during magnetic compass orientation are part of an ascending visual processing stream, the thalamofugal pathway. Furthermore, Cluster N seems to be a specialized part of the visual wulst. These findings strongly support the hypothesis that migratory birds use their visual system to perceive the reference compass direction of the geomagnetic field and that migratory birds “see” the reference compass direction provided by the geomagnetic field.

PLOS ONE

1238870

10.1093/JXB/ERI022

Plasticity in light reactions of photosynthesis for energy production and photoprotection.

Plant photosynthesis channels some of the most highly reactive intermediates in biology, in a way that captures a large fraction of their energy to power the plant. A viable photosynthetic apparatus must not only be efficient and robust machinery, but also well integrated into the plant's biochemical and physiological networks. This requires flexibility in its responses to the dramatically changing environmental conditions and biochemical demands. First, the output of the energy-storing light reactions must match the demands of plant metabolism. Second, regulation of the antenna must be flexible to allow responses to diverse challenges that could result in excess light capture and subsequent photoinhibition. Evidence is presented for the interplay of two types of mechanistic flexibility, one that modulates the relative sensitivity of antenna down-regulation to electron flow, and the other, which primarily modulates the output ratio of ATP/NADPH, but also contributes to down-regulation.

Journal of Experimental Botany

3399817

10.1016/J.PARINT.2007.09.009

Hemozoin: oil versus water.

Because the quinolines inhibit heme crystallization within the malaria parasite much work has focused on mechanism of formation and inhibition of hemozoin. Here we review the recent evidence for heme crystallization within lipids in diverse parasites and the new implications of a lipid site of crystallization for drug targeting. Within leukocytes hemozoin can generate toxic radical lipid metabolites, which may alter immune function or reduce deformability of uninfected erythrocytes.

Parasitology International

55388467

10.1098/RSTB.1998.0313

Vertical jumping in Galago senegalensis: the quest for an obligate mechanical power amplifier

Bushbabies ( Galago senegalensis ) are renowned for their phenomenal jumping capacity. It was postulated that mechanical power amplification must be involved. Dynamic analysis of the vertical jumps performed by two bushbabies confirms the need for a power amplifier. Inverse dynamics coupled to a geometric musculo–skeletal model were used to elucidate the precise nature of the mechanism powering maximal vertical jumps. Most of the power required for jumping is delivered by the vastus muscle–tendon systems (knee extensor). Comparison with the external joint–powers revealed, however, an important power transport from this extensor (about 65%) to the ankle and the midfoot via the bi–articular calf muscles. Peak power output likely implies elastic recoil of the complex aponeurotic system of the vastus muscle. Patterns of changes in length and tension of the muscle–tendon complex during different phases of the jump were found which provide strong evidence for substantial power amplification (times 15). It is argued here that the multiple internal connective tissue sheets and attachment structures of the well–developed bundles of the vastus muscle become increasingly stretched during preparatory crouching and throughout the extension phase, except for the last 13 ms of the push–off (i.e. when power requirements peak). Then, tension in the knee extensors abruptly falls from its maximum, allowing the necessary fast recoil of the tensed tendon structures to occur.

Philosophical Transactions of the Royal Society B

11345205

10.1371/JOURNAL.PONE.0003446

Functional Dorsoventral Symmetry in Relation to Lift-Based Swimming in the Ocean Sunfish Mola mola

The largest (up to 2 tons) and a globally distributed teleost—the ocean sunfish Mola mola—is commonly regarded as a planktonic fish because of its unusual shape including absence of caudal fin. This common view was recently questioned because the horizontal movements of the ocean sunfish tracked by acoustic telemetry were independent of ocean currents. However, direct information regarding their locomotor performance under natural conditions is still lacking. By using multi-sensor tags, we show that sunfish indeed swam continuously with frequent vertical movements at speeds of 0.4–0.7 m s–1, which is similar to the records of other large fishes such as salmons, marlins, and pelagic sharks. The acceleration data revealed that they stroked their dorsal and anal fins synchronously (dominant frequency, 0.3–0.6 Hz) to generate a lift-based thrust, as penguins do using two symmetrical flippers. Morphological studies of sunfish (mass, 2–959 kg) showed that the dorsal and anal fins had similar external (symmetrical shape and identical area) and internal (identical locomotory muscle mass) features; however, the muscle shape differed markedly. We conclude that ocean sunfish have functional dorsoventral symmetry with regards to the non-homologous dorsal and anal fins that act as a pair of vertical hydrofoils. Although sunfish lack a swimbladder, we found that they are neutrally buoyant independent of depth because of their subcutaneous gelatinous tissue that has low density and is incompressible. Efficient lift-based swimming in conjunction with neutral buoyancy enables sunfish to travel long distances both horizontally and vertically.

PLOS ONE

85924764

10.1016/S0006-3495(01)76093-6

Modeling Pseudomonas syringae Ice-Nucleation Protein as aβ-Helical Protein

Antifreeze proteins (AFPs) inhibit the growth of ice, whereas ice-nucleation proteins (INPs) promote its formation. Although the structures of several AFPs are known, the structure of INP has been modeled thus far because of the difficulty in determining membrane protein structures. Here, we present a novel model of an INP structure from Pseudomonas syringae based on comparison with two newly determined insect AFP structures. The results suggest that both this class of AFPs and INPs may have a similar beta-helical fold and that they could interact with water through the repetitive TXT motif. By theoretical arguments, we show that the distinguishing feature between an ice inhibitor and an ice nucleator lies in the size of the ice-interacting surface. For INPs, the larger surface area acts as a template that is larger than the critical ice embryo surface area required for growth. In contrast, AFPs are small enough so that they bind to ice and inhibit further growth without acting as a nucleator.

Biophysical Journal

25571137

10.1073/PNAS.0904304106

Divergent investment strategies of Acacia myrmecophytes and the coexistence of mutualists and exploiters

Ant-plant interactions represent a diversity of strategies, from exploitative to mutualistic, and how these strategies evolve is poorly understood. Here, we link physiological, ecological, and phylogenetic approaches to study the evolution and coexistence of strategies in the Acacia–Pseudomyrmex system. Host plant species represented 2 different strategies. High-reward hosts produced significantly more extrafloral nectar (EFN), food bodies, and nesting space than low-reward hosts, even when being inhabited by the same species of ant mutualist. High-reward hosts were more effectively defended against herbivores and exploited to a lower extent by nondefending ants than low-reward hosts. At the phenotypic level, secretion of EFN and ant activity were positively correlated and a mutualistic ant species induced nectar secretion, whereas a nondefending exploiter did not. All of these mechanisms contribute to the stable association of high-reward hosts with defending ant species. However, exploiter ants are less dependent on the host-derived rewards and can colonize considerable proportions of the low-reward hosts. Mapping these strategies onto phylogenetic trees demonstrated that the low-reward hosts represent the derived clade within a monophyletic group of obligate ant plants and that the observed exploiter ant species evolved their strategy without having a mutualistic ancestor. We conclude that both types of host strategies coexist because of variable net outcomes of different investment–payoff regimes and that the effects of exploiters on the outcome of mutualisms can, thus, increase the diversity within the taxa involved.

Proceedings of the National Academy of Sciences of the United States of America

15419778

10.1111/J.1463-5224.2004.00318.X

Comparative morphology of the tapetum lucidum (among selected species).

OBJECTIVES The phenomenon of 'eye-shine' is seen in a variety of animal species, and is generally thought to be related to the presence of an intraocular reflecting structure, the tapetum lucidum. The tapetum lucidum is a biologic reflector system that is a common feature in the eyes of vertebrates. It normally functions to provide the light-sensitive retinal cells with a second opportunity for photon-photoreceptor stimulation, thereby enhancing visual sensitivity at low light levels. The tapetum lucidum is presented here according to a classification based on the location, as well as the composition, of this reflective layer. Finally, the physical and chemical properties, as well as the origins of the different tapeta lucida, are discussed and compared. METHODS The anatomic and biochemical aspects of the tapetum lucidum in various vertebrates are examined. Morphologic observations were made from paraffin and plastic embedded specimens. Specimens were treated with traditional stains and observed by light and transmission electron microscopy. RESULTS Some species (primates, squirrels, birds, red kangaroo and pig) do not have this structure and they usually are diurnal animals. In vertebrates, the tapetum lucidum exhibits diverse structure, organization and composition. Therefore, the retinal tapetum (teleosts, crocodilians, marsupials, fruit bat), the choroidal guanine tapetum (elasmobranchs), the choroidal tapetum cellulosum (carnivores, rodents, cetacea), and the choroidal tapetum fibrosum (cow, sheep, goat, horse) are described. CONCLUSIONS The tapetum lucidum represents a remarkable example of neural cell and tissue specialization as an adaptation to a dim light environment and, despite these differences, all tapetal variants act to increase retinal sensitivity by reflecting light back through the photoreceptor layer. These variations regarding both its location and structure, as well as the choice of reflective material, may represent selective visual adaptations associated with their feeding behavior, in response to the use of specific wavelengths and amount of reflectance required.

Veterinary Ophthalmology

86287544

10.1641/0006-3568(2006)56[570:TIONCA]2.0.CO;2

The Implications of Niche Construction and Ecosystem Engineering for Conservation Biology

Abstract Although strategies to conserve biodiversity (e.g., the establishment of reserves and the management of flagship, umbrella, indicator, and keystone species) are valuable, they entail practical and conceptual difficulties. A focus on niche construction and ecosystem engineering, however, could provide new insights and methods for conservation biology. Many organisms modulate the availability of resources to other species by causing state changes in biotic or abiotic materials (ecosystem engineering), in the process frequently changing the selection to which the ecosystem engineers and other organisms are exposed (niche construction). We describe growing evidence that organisms have significant nontrophic impacts on ecosystem structure, function, and biodiversity, and outline established means of identifying key species involved in niche construction. On the basis of this engineering perspective, we propose a number of measures that could be employed to enhance conservation efforts.

BioScience

42220708

10.1016/0300-9629(86)90699-7

Freeze tolerance and intolerance as strategies of winter survival in terrestrially-hibernating amphibians.

The ability to tolerate extracellular freezing as an adaptation for winter survival was tested in seven species of terrestrially-hibernating amphibians found in eastern Canada. All species had only moderate supercooling abilities, with whole animal supercooling points of -1.5 to -3 degrees C. Two salamander species, Plethodon cinereus and Ambystoma laterale, and the toad, Bufo americanus, were freezing intolerant and were killed when frozen for 24 hr at temperatures just below their supercooling points. The major winter strategy of these animals appears to behavioural avoidance of subzero temperatures. Four species of frogs Rana sylvatica, Hyla versicolor, Hyla crucifer and Pseudacris triseriata, survived extracellular freezing at moderate subzero temperatures (-2 to -4 degrees C) for periods of time ranging up to 2 weeks. All four frog species accumulated low molecular weight carbohydrates as cryoprotectants, glycerol being the major cryoprotectant in adult H. versicolor, while immature adults of this species as well as the other three species all produced high levels of glucose as the cryoprotectant.

Comparative Biochemistry and Physiology Part A: Physiology

206523397

10.1126/SCIENCE.1181766

Cryo-EM Model of the Bullet-Shaped Vesicular Stomatitis Virus

VSV in 3D Rhabdoviruses are a family of negative-stranded RNA viruses that includes rabies virus, which have a characteristic bullet shape. Though structures of individual rhabdovirus proteins have been reported, how these are organized into a bullet shape has remained unclear. Now, Ge et al. (p. 689) report a cryo-electron microscopy structure of a model rhabdovirus, vesicular stomatitis virus. The structural data and examination of mutants allows modeling of virion assembly. The structure of a negative-strand RNA virus suggests how bullet-shaped rhabdoviruses assemble. Vesicular stomatitis virus (VSV) is a bullet-shaped rhabdovirus and a model system of negative-strand RNA viruses. Through direct visualization by means of cryo–electron microscopy, we show that each virion contains two nested, left-handed helices: an outer helix of matrix protein M and an inner helix of nucleoprotein N and RNA. M has a hub domain with four contact sites that link to neighboring M and N subunits, providing rigidity by clamping adjacent turns of the nucleocapsid. Side-by-side interactions between neighboring N subunits are critical for the nucleocapsid to form a bullet shape, and structure-based mutagenesis results support this description. Together, our data suggest a mechanism of VSV assembly in which the nucleocapsid spirals from the tip to become the helical trunk, both subsequently framed and rigidified by the M layer.

Science

17632933

10.1016/J.NEURON.2010.11.006

Deconstruction for Reconstruction: The Role of Proteolysis in Neural Plasticity and Disease

The brain changes in response to experience and altered environment. This neural plasticity is largely mediated by morphological and functional modification of synapses, a process that depends on both synthesis and degradation of proteins. It is now clear that regulated proteolysis plays a critical role in the remodeling of synapses, learning and memory, and neurodevelopment. Here, we highlight the mechanisms and functions of proteolysis in synaptic plasticity and discuss its alteration in disease states.

Neuron

13187871

10.1098/RSPB.2015.2200

Macroevolutionary assembly of ant/plant symbioses: Pseudomyrmex ants and their ant-housing plants in the Neotropics

Symbioses include some of the clearest cases of coevolution, but their origin, loss or reassembly with different partners can rarely be inferred. Here we use ant/plant symbioses involving three plant clades to investigate the evolution of symbioses. We generated phylogenies for the big-eyed arboreal ants (Pseudomyrmecinae), including 72% of their 286 species, as well as for five of their plant host groups, in each case sampling more than 61% of the species. We show that the ant-housing Vachellia (Mimosoideae) clade and its ants co-diversified for the past 5 Ma, with some species additionally colonized by younger plant-nesting ant species, some parasitic. An apparent co-radiation of ants and Tachigali (Caesalpinioideae) was followed by waves of colonization by the same ant clade, and subsequent occupation by a younger ant group. Wide crown and stem age differences between the ant-housing genus Triplaris (Polygonaceae) and its obligate ant inhabitants, and stochastic trait mapping, indicate that its domatium evolved earlier than the ants now occupying it, suggesting previous symbioses that dissolved. Parasitic ant species evolved from generalists, not from mutualists, and are younger than the mutualistic systems they parasitize. Our study illuminates the macroevolutionary assembly of ant/plant symbioses, which has been highly dynamic, even in very specialized systems.

Proceedings of The Royal Society B: Biological Sciences

36493946

10.1098/RSIF.2006.0135

Wet but not slippery: boundary friction in tree frog adhesive toe pads

Tree frogs are remarkable for their capacity to cling to smooth surfaces using large toe pads. The adhesive skin of tree frog toe pads is characterized by peg-studded hexagonal cells separated by deep channels into which mucus glands open. The pads are completely wetted with watery mucus, which led previous authors to suggest that attachment is solely due to capillary and viscous forces generated by the fluid-filled joint between the pad and the substrate. Here, we present evidence from single-toe force measurements, laser tweezer microrheometry of pad mucus and interference reflection microscopy of the contact zone in Litoria caerulea, that tree frog attachment forces are significantly enhanced by close contacts and boundary friction between the pad epidermis and the substrate, facilitated by the highly regular pad microstructure.

Journal of the Royal Society Interface

123543676

10.1364/JOSA.50.001005

Iridescent Colors of Hummingbird Feathers

The reflectance spectra of iridescent hummingbird feathers were measured spectrophotometrically for many species, and the structure of the iridescent parts of such feathers investigated by electron microscopy. In the direction normal to the iridescent feather surfaces the structure is found to be periodic in optical dimensions. It consists of stacks of 7–15 elliptical platelets of a material with refractive index ~2, each containing a structurally reinforced air gap. To interpret the reflectance spectra in terms of the surface structures, a theory is given of reflection coefficients of stratified media with analytic refractive-index variations. The theory is applied to the iridescence of hummingbird feathers and accounts quantitatively for the iridescent colors as interference colors by reflection from the observed feather structures.

Journal of the Optical Society of America

87453347

10.2307/1438539

On the Utility of the Saw of the Sawfish

cheeks and opercles silvery, the latter with bluish reflections; snout entirely transparent except at tip where there is some duskiness that extends a short way backward on sides. The colors have changed very little but there is no longer any silver on the opercles, which are black due to the black lining of the gill-cavity showing through the transparent bones. The specimen agrees with the excellent description of the type in all characters not mentioned above.

Copeia

10371214

10.1098/RSBL.2010.0167

The lantern shark's light switch: turning shallow water crypsis into midwater camouflage

Bioluminescence is a common feature in the permanent darkness of the deep-sea. In fishes, light is emitted by organs containing either photogenic cells (intrinsic photophores), which are under direct nervous control, or symbiotic luminous bacteria (symbiotic photophores), whose light is controlled by secondary means such as mechanical occlusion or physiological suppression. The intrinsic photophores of the lantern shark Etmopterus spinax were recently shown as an exception to this rule since they appear to be under hormonal control. Here, we show that hormones operate what amounts to a unique light switch, by acting on a chromatophore iris, which regulates light emission by pigment translocation. This result strongly suggests that this shark's luminescence control originates from the mechanism for physiological colour change found in shallow water sharks that also involves hormonally controlled chromatophores: the lantern shark would have turned the initial shallow water crypsis mechanism into a midwater luminous camouflage, more efficient in the deep-sea environment.

Biology Letters

34397388

10.2307/1543542

Adaptable Defense: A Nudibranch Mucus Inhibits Nematocyst Discharge and Changes With Prey Type

Nudibranchs that feed on cnidarians must defend themselves from the prey’s nematocysts or risk their own injury or death. While a nudibranch’s mucus has been thought to protect the animal from nematocyst discharge, an inhibition of discharge by nudibranch mucus has never been shown. The current study investigated whether mucus from the aeolid nudibranch Aeolidia papillosa would inhibit nematocyst discharge from four species of sea anemone prey. Sea anemone tentacles were contacted with mucus-coated gelatin probes, and nematocyst discharge was quantified and compared with control probes of gelatin only. Mucus from A. papillosa inhibited the discharge of nematocysts from sea anemone tentacles. This inhibition was specifically limited to the anemone species on which the nudibranch had been feeding. When the prey species was changed, the mucus changed within 2 weeks to inhibit the nematocyst discharge of the new prey species. The nudibranchs apparently produce the inhibitory mucus rather than simply becoming coated in anemone mucus during feeding. Because of the intimate association between most aeolid nudibranchs and their prey, an adaptable mucus protection could have a significant impact on the behavior, distribution, and life history of the nudibranchs.

The Biological Bulletin

2336043

10.1073/PNAS.12.3.207

The Physiological Principle of Minimum Work: I. The Vascular System and the Cost of Blood Volume.

Proceedings of the National Academy of Sciences of the United States of America

37772687

10.1007/BF00692371

Effect of blood removal and infusion on gull salt gland secretion

Summary1.The effect of blood removal and addition on salt gland secretion was studied in freshwater and seawater acclimated gulls,Larus glaucescens.2.In contrast to published reports that blood removal decreased and blood infusion increased salt gland secretion in ducks, neither blood removal nor addition had an effect on concentration or volume of salt gland secretion in gulls.

Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology

9404472

10.1086/316751

Thermoregulation by Kangaroos from Mesic and Arid Habitats: Influence of Temperature on Routes of Heat Loss in Eastern Grey Kangaroos (Macropus giganteus) and Red Kangaroos (Macropus rufus)

We examined thermoregulation in red kangaroos (Macropus rufus) from deserts and in eastern grey kangaroos (Macropus giganteus) from mesic forests/woodlands. Desert kangaroos have complex evaporative heat loss mechanisms, but the relative importance of these mechanisms is unclear. Little is known of the abilities of grey kangaroos. Our detailed study of these kangaroos' thermoregulatory responses at air temperatures (Ta) from −5° to 45°C showed that, while some differences occur, their abilities are fundamentally similar. Both species show the basic marsupial characteristics of relatively low basal metabolism and body temperature (Tb). Within the thermoneutral zone, Tb was \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$36.3^{\circ }\pm 0.1^{\circ }$$ \end{document} C ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $$\overline{X}\pm \mathrm{SE}\,$$ \end{document} ) in both species, and except for a small rise at Ta 45°C, Tb was stable over a wide range of Ta. Metabolic heat production was 25% higher in red kangaroos at Ta −5°C. At the highest Ta (45°C), both species relied on evaporative heat loss (EHL) to maintain Tb; both panting and licking were used. The eastern grey kangaroo utilised panting (76% of EHL) as the principal mode of EHL, and while this was so for red kangaroos, cutaneous evaporative heat loss (CEHL) was significant (40% of EHL). CEHL appeared to be mainly licking, as evidenced from surface temperatures. Both species utilised peripheral vascular adjustments to control heat flow, as indicated by changes in dry conductance (Cdry). At lower temperatures, Cdry was minimal, but it increased significantly at Ta just below Tb (33°C); in these conditions, the Cdry of red kangaroos was significantly higher than that of eastern grey kangaroos, indicating a greater reliance on dry heat loss. Under conditions where heat flows into the body from the environment (Ta 45°C), there was peripheral vasoconstriction to reduce this inflow; Cdry decreased significantly from the values seen at 33°C in both kangaroos. The results indicated that, while both species have excellent thermoregulatory abilities, the desert red kangaroos may cope better with more extreme temperatures, given that they respond to Ta 45°C with lower respiratory evaporation than do the eastern grey kangaroos.

Physiological and Biochemical Zoology

16751007

10.1038/SREP08495

Defoliation of interior Douglas-fir elicits carbon transfer and stress signalling to ponderosa pine neighbors through ectomycorrhizal networks

Extensive regions of interior Douglas-fir (Pseudotsuga menziesii var. glauca, IDF) forests in North America are being damaged by drought and western spruce budworm (Choristoneura occidentalis). This damage is resulting from warmer and drier summers associated with climate change. To test whether defoliated IDF can directly transfer resources to ponderosa pine (Pinus ponderosae) regenerating nearby, thus aiding in forest recovery, we examined photosynthetic carbon transfer and defense enzyme response. We grew pairs of ectomycorrhizal IDF ‘donor’ and ponderosa pine ‘receiver’ seedlings in pots and isolated transfer pathways by comparing 35 μm, 0.5 μm and no mesh treatments; we then stressed IDF donors either through manual defoliation or infestation by the budworm. We found that manual defoliation of IDF donors led to transfer of photosynthetic carbon to neighboring receivers through mycorrhizal networks, but not through soil or root pathways. Both manual and insect defoliation of donors led to increased activity of peroxidase, polyphenol oxidase and superoxide dismutase in the ponderosa pine receivers, via a mechanism primarily dependent on the mycorrhizal network. These findings indicate that IDF can transfer resources and stress signals to interspecific neighbors, suggesting ectomycorrhizal networks can serve as agents of interspecific communication facilitating recovery and succession of forests after disturbance.

Scientific Reports

136935606

10.1016/S1672-6529(11)60018-8

Mechanism of infrared detection and transduction by beetle Melanophila Acuminata

The Melanophila acuminata beetle is attracted to forest fires via a pair of infrared sensory organs composed of sensilla. Our histological work showed that each sensillum contains lipid layers surrounding a protein layer and a unique polysaccharide base that is associated with a neuron to each sensillum. Infrared microscopy showed that the protein region maximally absorbs infrared radiation at 3 μm wavelength and at 10 μm, which corresponds to the known radiation produced by forest fires at 3 μm. Mathematical calculations showed that the physical properties of the sensilla are such that the expected temperature rise is insufficient for transduction of the infrared signal through mechanical means or as a thermal receptor as previously thought; hence the protein plays the pivotal role in perception of single photons and transmission of the signal within the sensilla.

Journal of Bionic Engineering

27954855

10.1007/BF01632816

Functional morphology and movements of the proboscis of Lepidoptera (Insecta)

SummaryThe mouthparts of Lepidoptera were investigated in a number of species by morphological and cinematographical methods. Both the galeae (which compose the proboscis) and the basal maxillary components (stipites) were studied in the resting position, in motion, and during feeding. In the resting position the proboscis is coiled so tightly that the surfaces of the consecutive coils are in close contact and the outermost coil touches the ventral side of the head. Cuticular processes of the galeal wall interlock between the coils in this position. In the investigated species they occur on the galeal wall and on the ventral side of the head in varying number and distribution. By the extension of the basal galeal joint, the coiled proboscis is released from its resting position and is elevated continuously. It uncoils in 3–5 steps which effect the entire length simultaneously. Each uncoiling step occurs synchronously with a compression of the stipital tubes on either side of the body. These compression movements pump hemolymph into the galeae. In all investigated Lepidoptera the uncoiled proboscis shows a distinct downward bend at a certain point which is also detectable in anaesthetized or freshly killed animals in some species. This feeding position and the movements of the uncoiled proboscis are similar in all species despite the intrinsic galeal muscles being variously arranged in the galeal lumen in different Lepidoptera. When comparing cross-sections through corresponding regions of coiled and uncoiled proboscises, the curvatures of the dorsal galeal walls remain unchanged. Coiling of the proboscis starts at the tip and progresses to the base. After coiling the proboscis tightly beneath the head, the diameter of the spiral widens due to its elastic properties until the proboscis props itself against the ventral side of the head. This elastic effect combined with the interlocking cuticular processes seems to be responsible for the resting position of the proboscis.

Zoomorphology

16566726

10.1093/ICB/ICL030

Revisiting synchronous gamete release by fucoid algae in the intertidal zone: fertilization success and beyond?

In the marine environment, both external fertilization and settlement are critical processes linking adult and early juvenile life-history phases. The success of both processes can be tightly linked in organisms lacking a larval dispersive phase. This review focuses on synchronous gamete release (= spawning) in fucoid algae. These brown macroalgae are important components of temperate intertidal ecosystems in many parts of the world, and achieve synchronous gamete release by integrating various environmental signals. Photosynthesis-dependent sensing of boundary-layer inorganic carbon fluxes, as well as blue light and green light signals, possibly perceived via a chloroplast-located photoreceptor(s), are integrated into pathways that restrict gamete release to periods of low water motion. Avoidance of turbulent and/or high flow conditions in the intertidal zone allows high levels of fertilization success in this group. Temporal patterns and synchrony of spawning in natural populations are reviewed. Most species/populations have a more or less semilunar periodicity, although phase differences occur both between and within species at different geographical locations, raising the possibility that tidal and diurnal cues are more important than semilunar cues in entraining the response. The ecological and evolutionary role(s) of synchronous spawning in the intertidal zone are considered, particularly with regard to hybridization/reproductive isolation in species complexes, and reproductive versus recruitment assurance in the intertidal zone, where synchronous spawning during calm periods may be important for recruitment assurance in addition to fertilization success. Ways in which the roles of spawning synchrony could be tested in closely related species with contrasting mating systems (outcrossing versus selfing) are discussed.

Integrative and Comparative Biology

46327206

10.1016/J.GENE.2015.12.061

Epithelial sodium channel (ENaC) family: Phylogeny, structure-function, tissue distribution, and associated inherited diseases.

The epithelial sodium channel (ENaC) is composed of three homologous subunits and allows the flow of Na(+) ions across high resistance epithelia, maintaining body salt and water homeostasis. ENaC dependent reabsorption of Na(+) in the kidney tubules regulates extracellular fluid (ECF) volume and blood pressure by modulating osmolarity. In multi-ciliated cells, ENaC is located in cilia and plays an essential role in the regulation of epithelial surface liquid volume necessary for cilial transport of mucus and gametes in the respiratory and reproductive tracts respectively. The subunits that form ENaC (named as alpha, beta, gamma and delta, encoded by genes SCNN1A, SCNN1B, SCNN1G, and SCNN1D) are members of the ENaC/Degenerin superfamily. The earliest appearance of ENaC orthologs is in the genomes of the most ancient vertebrate taxon, Cyclostomata (jawless vertebrates) including lampreys, followed by earliest representatives of Gnathostomata (jawed vertebrates) including cartilaginous sharks. Among Euteleostomi (bony vertebrates), Actinopterygii (ray finned-fishes) branch has lost ENaC genes. Yet, most animals in the Sarcopterygii (lobe-finned fish) branch including Tetrapoda, amphibians and amniotes (lizards, crocodiles, birds, and mammals), have four ENaC paralogs. We compared the sequences of ENaC orthologs from 20 species and established criteria for the identification of ENaC orthologs and paralogs, and their distinction from other members of the ENaC/Degenerin superfamily, especially ASIC family. Differences between ENaCs and ASICs are summarized in view of their physiological functions and tissue distributions. Structural motifs that are conserved throughout vertebrate ENaCs are highlighted. We also present a comparative overview of the genotype-phenotype relationships in inherited diseases associated with ENaC mutations, including multisystem pseudohypoaldosteronism (PHA1B), Liddle syndrome, cystic fibrosis-like disease and essential hypertension.

Gene

20792900

10.1016/J.CEB.2012.09.006

Microtubule catastrophe and rescue.

Microtubules are long cylindrical polymers composed of tubulin subunits. In cells, microtubules play an essential role in architecture and motility. For example, microtubules give shape to cells, serve as intracellular transport tracks, and act as key elements in important cellular structures such as axonemes and mitotic spindles. To accomplish these varied functions, networks of microtubules in cells are very dynamic, continuously remodeling through stochastic length fluctuations at the ends of individual microtubules. The dynamic behavior at the end of an individual microtubule is termed 'dynamic instability'. This behavior manifests itself by periods of persistent microtubule growth interrupted by occasional switching to rapid shrinkage (called microtubule 'catastrophe'), and then by switching back from shrinkage to growth (called microtubule 'rescue'). In this review, we summarize recent findings which provide new insights into the mechanisms of microtubule catastrophe and rescue, and discuss the impact of these findings in regards to the role of microtubule dynamics inside of cells.

Current Opinion in Cell Biology

11692334

10.1016/S0005-2728(01)00203-1

Energy transfer and trapping in photosystem I.

The primary processes in all photosynthetic systems involve the absorption of energy from (sun) light by chromophores in a light harvesting antenna, and the subsequent transfer of this energy to a reaction centre (RC) site where the energy is `trapped' by means of a stable charge separation. Photosystem (PS) I is one of two such photosystems in oxygenic photosynthesis. When co-operating with PS II it uses the energy of light to transfer electrons from plastocyanin or soluble cytochrome c6 to ferredoxin and eventually to NADP‡. In an alternative pathway, the electrons from ferredoxin are transferred back to plastocyanin via the cytochrome b6f complex. This cyclic electron transport, which does not require the input of free energy by PS II, results in a transmembrane electrochemical gradient that can be used to produce ATP. In plants and green algae the PS I complex consists of two separable functional units: the PS I core, and the light harvesting complex (LHC) I peripheral antenna. The PS I complex in cyanobacteria does not possess the peripheral LHCI antenna, but since the PS I core complexes of cyanobacteria bear a large resemblance to the core complex of plants, a direct comparison of the energy transfer and trapping properties of these complexes is justi¢ed [1,2].

Biochimica et Biophysica Acta