Secretory activity in the oviductal epithelium of the stick insectCarausius morosus(Insecta, Phasmatodea)

Abstract

Abstract The oviduct of the stick insect Carausius morosus was examined ultrastructurally with a view to studying the secretory activity of the oviductal epithelium. Data presented in this study show that the oviduct in stick insects consists of a monolayered epithelium of columnar cells. On the luminal side, these cells are bordered by large clumps of secretory products. On the basal side, the oviductal cells are surrounded by a multilayered muscular sheath. At the ultrastructural level, secretory products appear to consist of electron dense, oblong granules resulting from self‐assembled rod‐shaped subunits. Within the granules, subunits are clustered in a parallel fashion so as to appear periodical in sections. Secretory activity in oviductal cells entails clustering of vesicles and tubular profiles along the cortical cytoplasm, followed by extracellular release of their contents at the apical plasma membrane. Injection of [35S]‐methionine into egg laying females resulted into labelling of all major protein fractions electrophoretically resolvable in the oviduct. Three major protein fractions became heavily labelled over the exposure time tested (from 4 to 96 h) in this study. These oviductal protein fractions were electroeluted from SDS‐gels and used to raise polyclonal antibodies in rabbits. These procedures allowed us to identify a 40 KD polypep‐tide as a major component of the secretory products bordering the oviductal cells. Results are interpreted and discussed in relation to the secretory potential of the stick insect oviduct for egg laying.