Cuticle Biology

We are interested in several topics, most were addressed by Bernard Moussian who is now at the University of Nizza. We are also active in the Royal Entomological Society’s Special Interest Group Arthropod Cuticle for who Klaus is a speaker.

1) Resilin, Copulatory Wounding and Sexual Coevolution

In sexual conflict, female defence against males is generally assumed to be resistance leading to trait exaggeration but not trait diversification. For the first time, we document tolerance in sexual conflict, a defence mechanism known from interspecific conflicts, exists in sexual conflict. We examined the traumatic insemination of female bed bugs, where males penetrate the cuticle during every mating, a textbook example of sexual conflict. Confocal laser scanning microscopy revealed large proportions of the soft and elastic protein resilin in the cuticle of the spermalege, the female defence organ. Reduced tissue damage and haemolymph loss were identified as adaptive female benefits from resilin. These did not arise from resistance because microindentation showed that the penetration force necessary to breach the cuticle was significantly lower at the resilin-rich spermalege than at other cuticle sites. Furthermore, a male survival analysis indicated that the spermalege did not impose antagonistic selection on males. Our findings suggest that the specific spermalege material composition evolved to tolerate the traumatic cuticle penetration. They demonstrate the importance of tolerance in sexual conflict and genitalia evolution, extend fundamental coevolution and speciation models and contribute to explaining the evolution of complexity.

See our paper.

2) The Ecology of the Insect Cuticle

The cuticle is the organ that contacts the environment. The chemistry, physiology and  structure of the cuticle are optimised to allow appropriate communication with environmental parameters. Different parts of the body are covered by different types of cuticle. The wings, for instance, are composed of a stiff but flexible cuticle, whereas the antennal cuticle is porous. To understand insect biology including behaviour, it is important to study the mechanical and physical properties of the cuticle that ultimately are the result of distinct molecular mechanisms deployed during insect development.

3) Chitin Synthesis

Chitin is considered as the defining molecule of Arthropod cuticle. It is a polysaccharide produced by the membrane-inserted chitin synthase that shows decent homologies to the plant cellulose synthase and the vertebrate hyaluronic acid synthase. Using the fruit fly Drosophila melanogaster, we have worked on the function of the chitin synthase in building the larval cuticle. Our analyses indicate that chitin is an essential scaffold element in the insect cuticle that contributes to the correct stratification of the cuticle. Its significance for the physical properties like elasticity and stiffness of the cuticle is under investigation.

In the last decade, several factors have been identified and characterised that assist chitin syntheses in chitin synthesis and/or chitin organisation. Knickkopf (Knk), for instance, is a membrane-anchored protein that is needed for chitin organisation into laminae.

4) Chitin and Chitosan Degradation

Most of this topic revolves around Reda’s PhD project who will be characterising the activity of chintin-degrading enzymes and its applicability to regulated chitosan break- down.

5) Injection Devices

More details coming soon. Here is just a brief thought to test how equivalent a spider fang (right) is with the bedbug’s copulatory dagger (left).

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