Growth and deposition of resilin and chitin in locust rubber-like cuticle

Abstract

Because of its simplicity, rubber-like cuticle offers good opportunities for studying problems of cuticle growth and deposition. Progress in this direction should lend impetus to subsequent studies of the more intricate solid cuticle. Although differing widely in physical and chemical properties, rubber-like and solid cuticles may nevertheless be compared with regard to their units and cycles of deposition. The growth of the protein rubber resilin and chitin has been measured quantitatively in two samples of rubber-like cuticle, and the results confirmed in sections analysed stratigraphically by means of daily growth layers. The cross-linking of the peptide chains of resilin, which establishes its three-dimensional molecular network, occurs continuously with deposition, in marked contrast to the bulk-tanning processes of solid exocuticle. Chitin deposition in rubber-like cuticle is quantal in nature, each chitin lamella representing a constant weight of chitin secreted by a constant population of epidermal cells. The deposition frequency of chitin lamellae is given as a function of age. Resilin and chitin deposition are analysed at the cellular level and a new perspective of cuticle growth is briefly outlined.