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

Numerical Modeling of the Collective Behavior of Scarab Beetles Transporting Dung Balls and Competing for Them on Complex Terrain

To avoid competition for the same food resource, scarab beetles form dung ball and roll it away from the dung pile. They randomly choose direction which they strictly follow. According to previous results, the dynamic behavior of the beetle rolling dung ball is essentially defined by the complexity of the surface. The typical real surface is combined from a universal scale invariant (fractal) component and another component having a well-defined characteristic scale. If the transported dung ball has a size comparable with the dimensions of peculiarities of the surface, it strongly influences the motion trajectory. On the flat terrain and at the absence of competitors, beetles manage to roll the ball along a nearly perfect straight path. However, even if the beetle is alone, on a more realistic terrain, the motion is more complex. The motion becomes much more complicated in the realistic situation, when the beetles complete for the balls. In this study, a numerical model is developed which combines 1) attraction of the beetles to the dung, (2) production of the balls of different sizes depending on the size/fitness of the animals, 3) the ball transportation on complex terrains, and 4) the competition between the beetles for already existing balls. A strong correlation between typical radius of the ball and the size of the relief minimums and the results of the competitions, as well as possible optimal strategies of the beetle behavior are found

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

Functional morphology of cirri in the barnacle Amphibalanus improvisus (crustacea: Balanidae)

Barnacles rely heavily on their mobile cirri for food capture because of the sessile lifestyle. These filamentous food capturing devices are extended into the water current and perform undulating movements. Cuticular structures with corresponding musculature work together, to allow these highly repetitive movements. This paper studies the interplay between structure and function of the cirri using scanning electron microscopy (SEM), microcomputed tomography (µCT) and high-speed video recordings (HSV) in Amphibalanus improvisus. Barnacles use the external cuticle structures (denticles and setae) for efficient grooming, food capturing, and providing support for the muscular system responsible for movement control. Entanglement of the cirri during extension is probably avoided through an interlocking of the serrate setae on cirri IV–VI, creating a “zipper-like” effect, which was recorded here using the HSV. We analyzed the muscular arrangement using µCT and found a new flexor muscle in both the endo- and exopod of cirrus II. Supported by the intrinsic cirral muscles, the new flexor muscles may provide variable movements of the anterior cirri (cirri I–III), which is important for further food handling. Our results provide a foundation for further comparative studies of the feeding apparatus of barnacles and for possible implications in the area of bio-inspired robotics

Conflicting Requirements for Transparency and Mechanical Stability in the Compound Eyes of Desert Locusts

Compound eyes of insects should be both thin and transparent to allow light to pass through, and at the same time mechanically stable to serve as exoskeleton. These conflicting requirements make the corneal cuticle an interesting example for studying cuticle biomechanics as well as for designing composite materials that seek similar properties. Here, scanning electron microscopy, confocal laser scanning microscopy, and nanoindentation are combined to investigate the microstructure, material composition, and material properties of the corneal cuticle of desert locust Schistocerca gregaria. The results suggest that a fully helicoidal architecture and large proportion of resilin in the corneal cuticle are likely to be adaptations for light transmission. Even though the corneal cuticle is resilin-rich, its elastic modulus is at least three times higher than that previously reported for other resilin-rich cuticles. This is likely due to the specific microstructure of the corneal cuticle with densely packed layers. This study presents one of a series of studies, in which multidisciplinary approaches are used to understand the link between the structure, material, property, and function in insect cuticle

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

WingSegment: A Computer Vision‐Based Hybrid Approach for Insect Wing Image Segmentation and 3D Printing

This article introduces WingSegment, a MATLAB app-designed tool employing a hybrid approach of computer vision and graph theory for precise insect wing image segmentation. WingSegment detects cells, junctions, Pterostigma, and venation patterns, measuring geometric features and generating Voronoi patterns. The tool utilizes region-growing, thinning, and Dijkstra's algorithms for boundary detection, junction identification, and vein path extraction. It provides histograms and box plots of geometric features, facilitating comprehensive wing analysis. WingSegment's efficiency is validated through comparisons with established tools and manual measurements, demonstrating accurate results. The tool further enables exporting detected boundaries as FreeCAD macro files for 3D modeling and printing, supporting finite element analysis. Beyond advancing insect wing morphology understanding, WingSegment holds broader implications for diverse planar structures, including leaves and geocells. This tool not only enhances automated geometric analysis and 3D model generation in insect wing studies but also contributes to the broader advancement of analysis, 3D printing, and modeling technologies across various planar structures

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