Comparison of adhesive organ of Idiosepius sp. and Euprymna scolopes

Histological, histochemical and ultrastructural methods were applied to elucidate the nature of the secretion in the epithelial cells of three Idiosepius species (I. biserialis, I. paradoxus and I. pygmaeus). Previous analysis of the adhesive organ of Euprymna scolopes by Singley (1982) reveals that adhesion and de-adhesion is caused by a duo-gland adhesive system. The epithelium of Idiosepius was studied to elucidate its morphology and the nature of its secretion. The current results show that the adhesive organ of Idiosepius consists of three different glandular cells and two non-secretory cell types. Histochemical results indicate that each glandular cell type contains sugar, associated with proteins. The nature of the secretory products suggests that all cell types are responsible for adhesion. Acid proteins were not found in the adhesive organ of Idiosepius. A duo-gland adhesive system as in Euprymna scolopes can therefore be excluded for Idiosepius. Idiosepius presumably uses the "Stefan-type" of adhesion. This form of adhesion involves the presence of two flat surfaces with a thin film of liquid in between. The different adhesive substances and mechanisms are discussed in relation to habitat choice and behaviour.