Furthermore, the stiffness gradient in wing veins, generated by a stiff, sclerotised outer layer exocuticle and a soft, compliant, resilin-bearing inner layer endocuticle is assumed to reduce the overall vein stiffness and to improve the damping properties of the vein as well as to delay Brazier ovalisation and to enhance the load-bearing capacity under large deformations [79,88]. By artificially stiffening single flexible, resilin-bearing vein joints in bumblebee wings through the application of micro-splints extra-fine polyester glitter glued with cyanoacrylate , it was experimentally shown that even a single resilin-bearing joint plays an important role in overall wing flexibility and vertical aerodynamic force production .
Ma et al. Based on the distribution of resilin patches, wing veins, the occurrence of a flexible hook-mediated forewing—hindwing connection and observed wing deformations, they further suggested the existence of five flexion lines in one forewing—hindwing entity and assumed that these probably increase the cordwise flexibility and support camber formation.
In addition, Mountcastle and Combes  demonstrated that a resilin-bearing joint at the leading edge the costal break in the wings of wasps plays a major role in mitigating wing wear by flexion along this joint when the wings hit an obstacle. This mechanism is especially important for wings with wing veins extending all the way to the tip because such a design endows a wing with more spanwise rigidity than, for example, bumblebee wings that lack veins at the wing tip .
The occurrence of resilin in several broadened vein patches as well as in membranous folding lines was described for fan-like dermapteran hind wings [22,92]. These structures help folding the wing into a wing package being ten times smaller than the unfolded wing. This package can then be hidden under the short sclerotised forewings. The four-fold wing folding can be achieved without musculature activity and is assumed to be driven by elastic recoil of the anisotropically distributed resilin on either the ventral or the dorsal sides of broadened vein patches in intercalary and radiating veins, supported by the resilin-bearing radiating folds that influence the folding direction .
Unfolding of the hind wings is achieved either by wiping movements of the cerci e. Both unfolding mechanisms are supported by several wing stiffening mechanisms such as the mid-wing mechanism and the claval flexion line, which keep the wing unfolded in all species examined [22,93]. These mechanisms were found to play an important role both in the static unfolded state of the wing and during flapping flight, in which they help to inhibit an unfavorable folding of the wing .
Furthermore, the flexible resilin-bearing folding lines were found to not only serve wing folding but also act as flexion lines at which the wing flexes during flight, thereby supporting the generation of an aerodynamically favourable cambered wing profile [92,94]. In beetle wings, resilin was found to occur at the marginal joint, between veins that separate during folding, and along flexion lines in membranous areas, leading to the hypothesis that elastic energy storage by resilin can support wing unfolding also in beetle wings .
Like in dermapteran wings, in beetle wings resilin most probably delays material fatigue in highly stressed wing regions and might further play a role in wing deformation during flight . In wings of the urban bluebottle blowfly Calliphora vicina , resilin is mainly present in the proximal part of the wing, predominantly in the form of resilin-bearing patches between veins .
The occurence of resilin coincides with the proximal distribution of the maximum spanwise bending stress at the beginning of each stroke cycle and suggests that the resilin patches reduce the risk of breaking near the wing hinge due to a decrease in peak stress in the rigid wing parts .
The contact formation of insect adhesive pads on substrates depends on the ability of the pads to adapt to the surface topography. In this context, specific micro- and nanostructures can enhance the quality of the contact . In the case of attachment on rough substrates, multiple contacts, being formed by some adhesive systems, provide great advantages . The formation of multiple contacts, which contribute to an increase of the overall length of the total peeling line, is facilitated by a hierarchical organisation of the attachment structures .
It was shown that the combination of thin tape-like contact tips of hairs setae and applied shear force lead to the formation of a maximal real contact area without slippage within the contact . This indicates that material flexibility is very important for the contact formation of adhesive pads. With a minimal normal load, flexible materials can create a large contact area between the attachment structures and the substrate. However, elongated structures that are too flexible have a low mechanical stability .
For example, if insect setae are too soft, they can buckle and collapse, and so-called clusterisation or condensation can take place [,]. As a result of this, the functional advantages achieved through multiple adhesive contacts can be strongly reduced .
Accordingly, the composition and the properties of the material of insect adhesive setae represent an optimisation problem. There is evidence that during the evolution gradients of the thickness and the mechanical properties of the setae have developed as a solution of this problem. The presence of thickness gradients, revealed by scanning electron microscopy, is well-known for various insect adhesive setae . The material of the setal tip contains large proportions of resilin, while the base of the seta consists mainly of sclerotised chitinous material.
Between the tip and the base, a pronounced material composition gradient was revealed by CLSM. This gradient is reflected by a pronounced gradient of the material properties: the setal tip is rather soft, whereas the setal base is relatively stiff. Both gradients were hypothesised to represent an evolutionary optimisation that increases the attachment performance of the adhesive pads when they attach to rough surfaces due to an efficient adaptation of the soft and flexible setal tips to the substrate and a simultaneous prevention of setal clusterisation by means of the stiffer setal bases .
Tarsal liquids produced by beetles are assumed to contribute to the adhesion efficiency of adhesive pads in the form of capillary interactions and cleaning effects. With regard to the resilin-dominated setal tips, an additional function is conceivable.
As described above, resilin is only soft and flexible when it is hydrated. Accordingly, to keep the contribution of the large resilin proportions in the setal tips to the attachment performance of the adhesive pads on a high level, the hydration of the resilin must be maintained. It is imaginable that this is achieved by slowly evaporating tarsal liquids covering the setae and thereby keeping the resilin in the setal tips hydrated . The presence of material gradients has also been demonstrated for smooth attachment devices of insects .
Interestingly, the gradients revealed in smooth adhesive pads of locusts and bush crickets differ from those existing in the adhesive tarsal setae described above. The smooth pads contain a relatively soft core, which is covered by a stiffer layer. Accordingly, the direction of the material gradient is opposite to that in the adhesive tarsal setae, which can be well explained by the different pad architecture. Smooth pads feature branching fibres rods that form foam-like structures. The spaces between the solid structures are filled with fluid.
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Due to this construction principle, the pads are kept in shape. The fibres are terminated by a relatively stiff superficial layer that keeps the positions of the relatively long and thin fibres and thereby the distance between the fibre tips constant [23,]. Both pads possess a flexible resilin-containing exocuticle with fibrils that are fused into relatively large rods oriented in an angle to the surface.
However, slight differences in the pad architecture exist. Adhesive pads of L. The lower adhesive properties of L. The superficial layer is assumed to also protect the pad from desiccation as indicated by experiments showing that cut-off adhesive pads of T. Consequently, the material gradient provides a combination of conformability to the surface roughness of the substrate The compliant material of the pad contributes to the efficient contact formation with the substrate. Such pad architectures likely depend on the preferred environment of each species and are the result of trade-offs between different factors such as evaporation rate, stiffness, stability and adhesion.
- Functional diversity of resilin in Arthropoda.
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Figure 6: Material structure and properties of orthopteran adhesive pads euplantulae. A, B Great green bush-cricket Tettigonia viridissima. C, D Migratory locust Locusta migratoria. A, C Scanning electron micrographs showing frozen, fractured, substituted, dehydrated and critical point dried pads. B, D Wide-field fluorescence micrographs showing frozen-cut pads. E Desiccation dynamics of tarsi and pieces of tibiae cut off the body in both species.
In F and G, the ends of the boxes define the 25th and 75th percentiles, the lines indicate the medians, and the error bars define the 10th and 90th percentiles. A—G Adapted with permission from  , copyright Springer. A, B Great green bu The first mouthpart-related structures containing resilin were already mentioned shortly after the description of resilin. In the respective studies, resilin was found in the salivary and feeding pumps of assassin bugs  cited in  , . Later, the findings were confirmed and complemented by additional information about the resilin distribution .
In these pumps, which enable the bugs to suck relatively large amounts of blood in a short time period and to inject proteolytic enzymes into prey or assaulters or to spit on the latter, the resilin-containing structures function as elastic spring antagonists to muscles. A similar function was described for resilin-containing structures present in the maxillipeds of decapod crustaceans . The movements of the flagella of these mouthparts influence the water flow through the gills as well as over chemoreceptors located on the head, and thereby they importantly contribute to active chemoreception and to signalling by distributing urine odours.
Each of the flagella is abducted by the contraction of a single muscle. Due to this abduction, a structure that contains relatively large resilin proportions and is located in the joint between the flagellum und the exopodite of the maxilliped is bent.
After relaxation of the muscle, this elastic structure recovers its original shape and moves the flagellum back to its resting position. In general, due to its very pronounced elasticity and fatigue resistance, resilin appears to be a very suitable material for exoskeleton structures that are typically intensively deformed for a rather large number of times during the lifetime of the organisms. A butterfly proboscis, for example, is tightly and spirally coiled when it is in its resting position .
For the uptake of food, hemolymph is pumped into the proboscis resulting in the generation of hydrostatic pressure that completely uncoils the proboscis  and strongly changes the shape of certain proboscis elements. During this process, dorsal parts of the proboscis are compressed.
These parts contain relatively large proportions of resilin and act as springs that cause the recoiling of the proboscis when the hydrostatic pressure is removed . A remarkable resilin-containing adhesive prey-capture device, which is formed by the elongated labium, exists in rove beetles of the genus Stenus Staphylinidae.
This prey-capture apparatus can be protruded towards a prey within a few milliseconds. When sticky pads modified paraglossae , which are located at the distal end of the prementum, adhere to the prey, the labium is withdrawn immediately, and thereby the prey is transported to the mouth region of the beetle where it can be seized with the mandibles . The sticky pads feature a surface that is subdivided into numerous terminally branched outgrowths. During the prey capture, these surface structures are completely covered by an adhesive secretion that is produced in special glands located in the head capsule and makes the sticky pads a hairy, hierarchically structured and wet adhesive system.
Similar to the insect tarsal adhesive pads mentioned above, softness and compliance of the pad cuticle contribute to the generation of strong adhesive forces by the pads. The cuticle material of certain parts of the sticky pads contains large proportions of resilin providing flexibility and elasticity and enabling the pads to efficiently adapt to the surface of the prey items . Copepods are tiny crustaceans that inhabit nearly all aquatic habitats worldwide and are particularly abundant in the marine water column where they contribute large proportions of the zooplankton [,].
The diet of many of the marine planktonic species comprises relatively large fractions of diatoms i. Copepods use the gnathobases of their mandibles to grab and mince food particles. To be able to efficiently digest the diatom cells, the copepods must crack the frustules before the ingestion of the cells. The gnathobases possess tooth-like structures called teeth in the following at their distal ends .
In copepod species feeding on large amounts of diatoms, these teeth are rather compact and consist of complex composites that combine diverse structures and materials with a wide range of properties. Recently, the morphology and material composition of the gnathobases of two copepod species have been analysed and described in great detail [29,30]. Each of these teeth possesses a chitinous socket, which is covered by a cap-like structure with a large resilin proportion.
On top, another cap-like structure that is composed of silica is located. All other gnathobase teeth are smaller, contain no silica, are mainly chitinous and have tips with large resilin proportions. It is assumed that the large silica-containing teeth are used for feeding on diatoms. The silica makes these teeth stiffer and more mechanically stable and thereby more efficient in cracking the diatom frustules.
In case the diatom frustules are too stable and the pressure acting on the tips of the siliceous teeth exceeds the breaking stress level causing an increased risk of crack formation in and breakage of the teeth, the soft and elastic resilin-containing structures are supposed to function as flexible bearings that can be compressed and thereby reduce stress concentrations in the tooth material and increase the resistance of the teeth to mechanical damages.
Additional structures with large resilin proportions, located in the central and proximal parts of the gnathobases, are assumed to have a damping function that makes the whole gnathobases resilient and further reduces the risk of mechanical damage of the teeth. The smaller gnathobase teeth of C. In this context, the grip of the tooth tips is suggested to be increased by the soft and elastic resilin making the grabbing process more efficient. Figure 7: Morphology and material composition of mandibular gnathobases of copepods.
Confocal laser scanning micrographs showing gnathobase structures of A—E a female of the copepod species Centropages hamatus and F, G a female of the copepod species Rhincalanus gigas. A—C, F, G Maximum intensity projections. A, F Distribution of resilin. B Chitinous exoskeleton red and resilin-dominated structures blue. C—E, G Chitinous exoskeleton red, orange , resilin-dominated structures blue, light blue, turquoise and silica-containing structures green.
A—E Adapted with permission from . F, G Adapted with permission from  , copyright Elsevier. Confocal laser scanning The gnathobases of the calanoid copepod Rhincalanus gigas , a species whose diet mainly consists of diatoms, are characterised by five relatively large and compact teeth that possess a combination of different materials comparable to that of the silica-containing teeth of C. Each of these teeth has a silica-containing cap-like structure, which is located on a chitinous socket. At the base of the socket, the gnathobase exoskeleton features large proportions of resilin.
Like in the silica-containing teeth of C. In general, the complex composite systems in the gnathobase teeth are assumed to have co-evolved within an evolutionary arms race together with the diatom frustules . The mating of bed bugs represents a famous example of sexual conflict. During every successful mating event, the cuticle of the ventral side of the abdomen of the female is penetrated by the male with a cannula-like intromittent organ, and the male injects sperm and accessory gland fluids directly into the abdomen where the sperm migrate to the ovaries [,].
This traumatic insemination imposes survival costs on the females  but the females cannot avoid mating . As a result of this sexual conflict, a female organ, the so-called spermalege, has evolved. In addition, evidence for a significantly reduced tissue damage and hemolymph loss was obtained for piercings of the spermalege cuticle compared with piercings of the other cuticle sites .
The results suggest that the material composition of the spermalege cuticle has evolved as a tolerance trait that reduces the mating costs of both the female and the male: due to the softness of resilin the penetration is easier for the male and causes less wounding of the female, and after the withdrawal of the intromittent organ the elasticity of resilin causes a sealing of the puncture reducing the hemolymph loss and the risk of bacterial infection. Figure 8: Material composition and properties of the ventral abdominal cuticle of females of the common bed bug Cimex lectularius.
A Abdomen overview scanning electron micrograph. B Section of A indicating the locations of the spermalege S and three other cuticle areas called AS, M and AM, and penetration forces mean ranks and standard errors determined for these four cuticle sites.
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C—L Confocal laser scanning micrographs maximum intensity projections showing overlays of different autofluorescences exhibited by the exoskeletons. Blue colours indicate large proportions of resilin. C, D Autofluorescence composition of the cuticle in the left C and right D abdomen parts. The cuticle at M and AM consists mainly of sclerotised chitinous material, indicated by the dominance of autofluorescence shown in red, while the presence of large proportions of autofluorescence shown in green in the cuticle at AS indicates that the respective material consists mainly of weakly or non-sclerotised chitinous material.
I—L Autofluorescence composition of the cuticle at the spermaleges of different one-week-old females, indicating variation of the extent of the resilin-dominated spermalege structures between females. Figure reproduced with permission from . Figure 8: Material composition and properties of the ventral abdominal cuticle of females of the common bed b Hair plate sensilla and campaniform sensilla are typical mechanoreceptors that are common in insect exoskeletons . These receptors possess so-called joint membranes and cap membranes that are composed of large proportions of resilin [10,,].
The base of each hair is surrounded by a joint membrane that, due to its resilin-dominated material composition, is soft and flexible and allows movement and bending of the hair shaft resulting in a stimulation of the receptor. Because the long hairs project beyond and below the pulvilli of the pretarsus, they touch the substrate shortly before the pulvilli and likely have the function to indicate the upcoming contact between the pulvilli and the substrate. The cerci of crickets feature cercal filiform hairs associated with campaniform sensilla [,]. Figure 9: Resilin in mechanoreceptors.
A—F Confocal laser scanning micrographs showing overlays of different autofluorescences exhibited by the exoskeletons. A Dorsal view of the pretarsus of a third leg of a female drone fly Eristalis tenax. The arrow highlights a hair plate sensillum. C Larger view of the hair plate sensillum highlighted in B. F Cercal filiform hair CFH and associated campaniform sensilla highlighted by small arrows on a cercus of a female house cricket Acheta domesticus.
A—C, F Maximum intensity projections. Figure reproduced with permission from  , copyright John Wiley and Sons. A—F Confocal laser scanning micrographs showing overlays of differen While other exoskeleton components are typically micro- and nano-structured, coloured and pigmented and, therefore, not suitable as material for optical elements, the pronounced transparency, the colourlessness and the amorphousness make resilin a perfect material for the construction of optical systems.
Figure Resilin in compound eyes. Confocal laser scanning micrographs maximum intensity projections depicting overlays of different autofluorescences exhibited by the exoskeleton. Blue structures contain large proportions of resilin. A Lateral view of the head of a male green lacewing Chrysoperla carnea. B Frontal view of the head of a pharaoh ant Monomorium pharaonis worker. C Lateral view of the head of a beetle of the genus Circocerus. Confocal laser scanning micrographs maximum intensity projections depic Exoskeleton structures with large proportions of resilin are common among arthropods.
This review demonstrates the broad range of resilin functions in various exoskeleton structures. Resilin facilitates flexibility and compliance, elastic energy storage, elastic recovery, fatigue and damage reduction, sealing and transparency and thereby makes the respective exoskeleton systems rather effective. Due to its remarkable combination of different properties, resilin is a highly efficient multi-functional protein. In addition, together with other compounds and materials, it often forms complex and powerful composites that combine the properties and benefits of the single components and are capable of performing rather specific and challenging functions.
These characteristics have very likely been the reason for the evolution of the large functional diversity of resilin-containing exoskeleton structures in arthropods.sehugdinadju.tk
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Stanislav N. Gorb and Thomas Speck. Gorb and Alexander E. Felix J. Epidemiological consequences of the ecological physiology of ticks. Sarah E. Appel - Vice chair: Colin M. Congratulations to Jonathan Voise for his prize as the best presentation in the session. See the publication page for his work. Congratulations as well to Teresita Insausti , who has a photo of a spider- crab published in the calendar edited by the Society for Experimental Biology! Read an Editorial Review on Amazon.
McCauley was with us for 6 months on 'Le Studium Chaire d'excellence'. He will work with J. Casas and others on different problems in population dynamics and integrative physiology, from understanding the biotic integrity of the Loire river, to multitrophic interactions on alpine insects to particle tracking in Daphnia.
David Giron recently got his Leding Research Habilitation entitled: A multidimensional dynamic approach to the nutritional ecology of insects: from host- parasitoid to plant- insect interactions. Back up. Laurence, from the Agrocampus Ouest of Rennes, will be doing her research training with us.
Florence is from the Master2 Insect Tours and will be doing her research training with us as well. Casas and including D. The Perry Adkisson Award was conceived to promote excellence in faculty research in the diverse sub- disciplines of Entomology. Activities of the Group. Not available. The Casas Group - People from left to right: To be listed.
Sex Ratio in the Group - This did fluctuate drastically over the years, between some 0. Various Past Events :. Orians Congratulations to Jonathan Voise for his prize as the best presentation in the session biomechanics at the annual meeting of the SEB in glasgow Extensive collection of femtolitre pad secretion droplets in the beetle Leptinotarsa decemlineata allows nanolitre microrheology.
Slippery pores: anti-adhesive effect of nanoporous substrates on the beetle attachment system. Elena V. Temporary stay at various environmental humidities affects attachment ability of Colorado potato beetles Leptinotarsa decemlineata Coleoptera, Chrysomelidae Dagmar Voigt , Jan Schuppert , Steffen Dattinger , Stanislav N. Division of labour and sex differences between fibrillar, tarsal adhesive pads in beetles: effective elastic modulus and attachment performance.
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