The cuticle proteins of Lucilia cuprina: Stage specificity and immunological relatedness

Abstract

Proteins extracted from larval, pupal and adult cuticles of the sheep blowfly, Lucilia cuprina, have been compared electrophoretically and immunologically. Larval, pupal and adult cuticles each possess a largely unique set of cuticle proteins. Cuticles from the three larval instars contain some shared proteins; of the nine major 3rd instar larval cuticle proteins, three appear to be present in the 1st instar and four in the 2nd instar. Immunological evidence suggests that these proteins are specific to the integument (i.e. to the epidermis plus cuticle) and are not transported to the cuticle via the haemolymph. Pupariation involves a concerted crosslinking of the major larval cuticle proteins, such that most extractable protein is rendered insoluble within 24 h of white puparium formation. Protein extracted from pupal cuticle resolves into seven major bands and that from adult cuticle into nine major bands on native polyacrylamide gels. The electrophoretic profile of proteins extracted from the pupal cuticle (which remains unsclerotized) is relatively constant throughout pupal life. In contrast, the profiles of proteins extracted from the adult cuticle (which becomes sclerotized) change markedly during development. Regional variation in pupal and adult cuticle protein composition is also found. Immunological cross-reactivity is obtained between an antiserum raised against L. cuprina larval cuticle proteins and proteins from the larval cuticle of Drosophila melanogaster.