Comparative study of some expanding arthropod cuticles: The relation between composition, structure and function

Abstract

The abdominal cuticles of the adult female ticks Argas (Persicargas) robertsi and Boophilus microplus, sp der Badumna insignis, tsetse fly Glossina morsitans morsitans, sheep ked Melophagus ovinus and locust Locusta migratoria migratorioides and of the fifth-instar larva of the bug Rhodnius prolixus stretch greatly, some of them quite rapidly, when they are feeding, laying eggs or carrying a developing larva or egg mass. During this expansion the epicuticle, which is convoluted, unfolds and the underlying endocuticle stretches. There is an increase in the volume of each of the cuticles on expansion. The fine structures of those cuticles which go through cycles of expansion and contraction do not become disrupted. Cuticles with acidic proteins have much higher chitin contents than those with basic proteins. Plasticization, i.e. breaking of intermolecular non-covalent bonds, precedes rapid expansion of cuticles but is unnecessary for slow expansion. The compositions of the cuticles and the properties of the proteins are discussed in relation to the expansions which take place in the cuticles.