Mandibular gnathobases of marine planktonic copepods – feeding tools with complex micro- and nanoscale composite architectures

Copepods are dominant members of the marine zooplankton. Their diets often comprise large proportions of diatom taxa whose silicified frustules are mechanically stable and offer protection against grazers. Despite of this protection, many copepod species are able to efficiently break even the most stable frustule types. This ability requires specific feeding tools with mechanically adapted architectures, compositions and properties. When ingesting food, the copepods use the gnathobases of their mandibles to grab and, if necessary, crush and mince the food items. The morphology of these gnathobases is related to the diets of the copepods. Gnathobases of copepod species that mainly feed on phytoplankton feature compact and stable tooth-like structures, so-called teeth. In several copepod species these gnathobase teeth have been found to contain silica. Recent studies revealed that the siliceous teeth are complex microscale composites with silica-containing cap-like structures located on chitinous exoskeleton sockets that are connected with rubber-like bearings formed by structures with high proportions of the soft and elastic protein resilin. In addition, the silica-containing cap-like structures exhibit a nanoscale composite architecture. They contain some amorphous silica and large proportions of the crystalline silica type α-cristobalite and are pervaded by a fine chitinous fibre network that very likely serves as a scaffold during the silicification process. All these intricate composite structures are assumed to be the result of a coevolution between the copepod gnathobases and diatom frustules in an evolutionary arms race. The composites very likely increase both the performance of the siliceous teeth and their resistance to mechanical damage, and it is conceivable that their development has favoured the copepods’ dominance of the marine zooplankton observed today

Subdivision of the neotropical Prisopodinae Brunner von Wattenwyl, 1893 based on features of tarsal attachment pads (Insecta, Phasmatodea)

The euplantulae of species from all five genera of the Prisopodinae Brunner von Wattenwyl, 1893 were examined using scanning electron microscopy with the aim to reveal the significance of attachment pads regarding their phylogenetic relationships. The split into the conventional two sister groups is supported by the two-lobed structure of the euplantulae with a smooth surface in the Prisopodini and a nubby surface microstructure in the Paraprisopodini. The two lineages are well distinguishable by this feature, as well as by the shape of the euplantulae themselves. The functional importance of the attachment pad surface features is discussed

Attachment devices and the tarsal gland of the bug Coreus marginatus (Hemiptera: Coreidae)

AbstractThe present ultrastructural investigation using scanning and transmission electron microscopy as well as light and fluorescence microscopy describes in detail the attachment devices and tarsal gland of the bug Coreus marginatus (L.) (Hemiptera: Coreidae). In particular, the fine structure of pulvilli reveals a ventral surface rich with pore channels, consistent with fluid emission, and a folded dorsal surface, which could be useful to enhance the pulvillus contact area during attachment to the substrate. The detailed description of the tarsal gland cells, whose structure is coherent with an active secretory function, allows us to consider the tarsal gland as the plausible candidate for the adhesive fluid production. Scolopidia strictly adhering to the gland cells are also described. On the basis of the fine structure of the tarsal gland, we hypothesise a fluid emission mechanism based on changes of the hydraulic pressure inside the gland, due to the unguitractor tendon movements. This mechanism could provide the fluid release based on compression of the pad and capillary suction, as demonstrated in other insects. The data here reported can contribute to understanding of insect adhesive fluid production, emission and control of its transport

Finite element analysis relating shape, material properties, and dimensions of taenioglossan radular teeth with trophic specialisations in Paludomidae (Gastropoda)

Altres ajuts: CERCA Programme/Generalitat de CatalunyaThe radula, a chitinous membrane with embedded tooth rows, is the molluscan autapomorphy for feeding. The morphologies, arrangements and mechanical properties of teeth can vary between taxa, which is usually interpreted as adaptation to food. In previous studies, we proposed about trophic and other functional specialisations in taenioglossan radulae from species of African paludomid gastropods. These were based on the analysis of shape, material properties, force-resistance, and the mechanical behaviour of teeth, when interacting with an obstacle. The latter was previously simulated for one species (Spekia zonata) by the finite-element-analysis (FEA) and, for more species, observed in experiments. In the here presented work we test the previous hypotheses by applying the FEA on 3D modelled radulae, with incorporated material properties, from three additional paludomid species. These species forage either on algae attached to rocks (Lavigeria grandis), covering sand (Cleopatra johnstoni), or attached to plant surface and covering sand (Bridouxia grandidieriana). Since the analysed radulae vary greatly in their general size (e.g. width) and size of teeth between species, we additionally aimed at relating the simulated stress and strain distributions with the tooth sizes by altering the force/volume. For this purpose, we also included S. zonata again in the present study. Our FEA results show that smaller radulae are more affected by stress and strain than larger ones, when each tooth is loaded with the same force. However, the results are not fully in congruence with results from the previous breaking stress experiments, indicating that besides the parameter size, more mechanisms leading to reduced stress/strain must be present in radulae

Air-entrapping capacity in the hair coverage of Malacosoma castrensis (Lasiocampidae: Lepidoptera) caterpillar: a case study.

The moth Malacosoma castrensis (Lasiocampidae) is commonly found along the Northern Germany coasts whose habitat is mainly represented by salt marshes subjected to sea level variations. Surprisingly, terrestrial caterpillars can withstand many hours being flooded by the seawater. The ability to withstand periods of submersion in a terrestrial insect raises the problem of respiration related to avoiding water percolation into the tracheal system. In the present study, we investigated under laboratory conditions the role of water-repellent cuticle structures in oxygen supply in caterpillars of M. castrensis submerged in water. For this purpose, air-layer stability tests using force measurements, and micromorphology of cuticle structures using SEM and fluorescence microscopy were performed. A plastron appeared when a caterpillar is under water. Plastron stability, its' gasses composition, and internal pressure were estimated. The plastron is stabilized by long and rare hairs, which are much thicker than the corresponding hairs of aquatic insects. Thick and stiff hairs with sclerotized basal and middle regions protrude into the water through plastron – water interface, while substantial regions of thin and flexible hairs are aligned along the plastron – water interface and their side walls can support pressure in plastron even below atmospheric pressure. Additional anchoring points between hair's stalk and microtrichia near to the hair base provide enhanced stiffness to the hair layer and prevent hair layer from collapse and water entering between hairs. Advancing contact angle on hairs is more than 90°, which is close to the effective contact angle for the whole caterpillar

Nanoporous monolithic microsphere arrays have anti-adhesive properties independent of humidity

Bioinspired artificial surfaces with tailored adhesive properties have attracted significant interest. While fibrillar adhesive pads mimicking gecko feet are optimized for strong reversible adhesion, monolithic microsphere arrays mimicking the slippery zone of the pitchers of carnivorous plants of the genus Nepenthes show anti-adhesive properties even against tacky counterpart surfaces. In contrast to the influence of topography, the influence of relative humidity (RH) on adhesion has been widely neglected. Some previous works deal with the influence of RH on the adhesive performance of fibrillar adhesive pads. Commonly, humidity-induced softening of the fibrils enhances adhesion. However, little is known on the influence of RH on solid anti-adhesive surfaces. We prepared polymeric nanoporous monolithic microsphere arrays (NMMAs) with microsphere diameters of a few 10 {\mu}m to test their anti-adhesive properties at RHs of 2 % and 90 %. Despite the presence of continuous nanopore systems through which the inner nanopore walls were accessible to humid air, the topography-induced anti-adhesive properties of NMMAs on tacky counterpart surfaces were retained even at RH = 90 %. This RH-independent robustness of the anti-adhesive properties of NMMAs significantly contrasts the adhesion enhancement by humidity-induced softening on nanoporous fibrillar adhesive pads made of the same material

Sexual Dimorphism in the Attachment Ability of Leptinotarsa decemlineata Say (Coleoptera, Chrysomelidae) on Rough Substrata

Leptinotarsa decemlineata lebt oligophag ausschließlich auf Vertretern der Solanaceae, insbesondere Solanum spp. (Radcliffe 1982). Die herbivore Spezies ist fähig, erfolgreich auf den unbehaarten, behaarten und glandulär behaarten Blattoberflächen der Nachtschattengewächse zu haften, sich fortzubewegen und zu leben. Dazu verhelfen paarige Krallen und Hafthaarkissen an den Tarsen (Rivnay 1928). Das ausgesprochen gute Haftvermögen und die Substratanpassungsfähigkeit haariger Haftsysteme von Insekten sind für verschiedene Vertreter der Diptera und Coleoptera experimentell belegt (siehe Review von Gorb 2001). Stork (1980 a, b) beobachtete insbesondere bei Käfern der Familien Chrysomelidae und Coccinellidae einen ausgeprägten Sexualdimorphismus der tarsalen Hafthaare. Schanz (1953) beschreibt für L. decemlineata drei verschiedene Hafthaartypen: (1) Haare mit sich asymmetrisch verjüngenden Spitzen, (2) spatelförmige Gebilde und (3) Haare mit Haftsohlen, welche nur die Männchen besitzen. Hinsichtlich der geschlechterspezifischen Unterschiede der Haftkraft auf verschieden rauen Oberflächen existieren bislang wenige quantitative Nachweise. Pelletier & Smilowitz (1987) wiesen für Männchen von L. decemlineata in Inversionsexperimenten ein außerordentliches Haftvermögen auf Glas- und Kunststoffoberflächen nach, wobei sie dessen Gründe in den maskulin-spezifischen Hafthaaren mit scheibenförmig verbreiterten Enden vermuteten. Die Fähigkeit der Männchen, an glatten Oberflächen besonders gut zu haften, wurde als eine Anpassung an die Haftung auf den glatten Oberflächen der Weibchenelytren während der Kopulation erklärt. Die meisten natürlichen Oberflächen (insbesondere Pflanzenoberflächen) sind jedoch rau. Somit besteht die Frage, ob beide Geschlechter auch eine unterschiedliche Spezialisierung der Haftsysteme für die Haftung auf rauen Substraten besitzen. Um den Einfluss unterschiedlicher Oberflächenrauhigkeiten auf die Haftsystemfunktionalität der Weibchen und Männchen von L. decemlineata zu prüfen, wurden in der vorliegenden Studie Kraftmessungen mit einzelnen Individuen auf Oberflächen mit exakt definierter Rauheit durchgeführt.The remarkable attachment ability and the adaptability to different substrates of insects‘ hairy attachment systems have been experimentally demonstrated in representatives of Diptera and Coleoptera. Many representatives from the family Chrysomelidae exhibit a distinctive sexual dimorphism in the structure of adhesive tarsal hairs. Differences in attachment ability between sexes have been previously reported for smooth substrata. In L. decemlineata, a very strong attachment ability on smooth glass and plastic surfaces has been described in males, and explained by the action of specialised mushroom-like tarsal hairs. The present study demonstrates the influence of different surface roughnesses on the attachment forces of L. decemlineata males and females. The maximum attachment force of individual beetles was measured on epoxy resin surfaces (0-12 μm surface roughness) using a centrifugal force tester. On the smooth surface, no considerable differences between males and females were found, whereas, on rough surfaces, adherence of females was significantly stronger, up to twice that of males. The results indicate that the main functional trait of the adhesive system of females is its stronger specialization to rough plant surfaces

METHODS OF THE PATTERN FORMATION IN NUMERICAL MODELING OF BIOLOGICAL PROBLEMS

Evolution of different systems can be described in terms of their relaxation to the minimums of some effective potential relief. This observation leads us to face us with a question how to generate corresponding potential patterns which describe adequately various physical and biological systems. In this review, we present a number of different ways of generating such potentials demanded by the problems of different kinds. For example, we reproduce such a generation in the framework of a simple theory of phase transitions, automatic blocking of the growing phase nucleation and universal large scale structure. Being frozen at late stages of their evolution they form majority of meta-stable structures which we observe in real world. Counting on above-mentioned universality of naturally-generated fractal structures and their further utilization in numerical simulations of biological problems, we reproduce also formal algorithms of generation of such structures based on random deposition technique and Fourier-transform approaches

Assessing Tolerance to the Hydrodynamic Exposure of Posidonia oceanica Seedlings Anchored to Rocky Substrates

Among a suite of abiotic and biotic factors, the hydrodynamic regime strongly influences the success of seagrass recruitment through sexual propagules. Uprooting of propagules by drag forces exerted by currents and waves is one of the main causes for the failed establishment and the consequent recruitment. Substrate type and stability play a key role in determining the success of colonization through sexual propagules, as seedling establishment probabilities proved to be significantly higher on rocky bottoms than on unstable unconsolidated substrates. In this research, the current and wave flow intensity that Posidonia oceanica seedlings anchored to rocky substrates can withstand before uprooting were evaluated and the influence of substrate complexity on seedling anchorage success and anchorage strength was investigated. P. oceanica seedlings withstood the current velocity of 70 cm s–1 and increased orbital flow velocities up to 25 cm s–1. Seedling adhesion strength ranged from 3.92 to 29.42 N. Results of the present study corroborate the hypothesis that substrate complexity at scales relevant to the size of propagules is a crucial feature for P. oceanica seedling establishment. The intensity of unidirectional and oscillatory flow that seedlings can withstand without being dislodged assessed in this study support the hypothesis that P. oceanica sexual propagules, once adhered to a consolidated substrate, are able to tolerate high hydrodynamic stress. The results of the present study contribute to re-evaluation of the habitat requirements of P. oceanica, assessing the range of hydrodynamic conditions that this species can tolerate during the early stages of its life history