Y-maze experiments on the chemotactic behaviour of the tetrabranchiate cephalopod Nautilus pompilius (Mollusca)

Abstract

In contrast to the modern cephalopods, the nautiloids use primarily the chemosensory sense to explore their environment. So far there have been few studies on sexual-selection processes in solitary-living nautiloid cephalopods, but it can be posited that conspecifics are also discovered by odour. In order to determine whether a special area of the rectum, the rectal gland, plays a role in the intraspecific communication processes of Nautilus pompilius, Y-maze experiments were performed. We tested the reaction of juvenile, early-adolescent male and female, and adult male N. pompilius to homogenates of the rectum of male and female conspecifics. As negative controls, homogenates of gills or mantle, or seawater were used. To check the set-up of the experiment, carrion was presented as a positive attractant. We demonstrated that the adult (mature) males significantly preferred the rectum homogenate containing the stimulus of females, whereas the homogenates from males and/or females had no influence on the behaviour of immature animals of both sexes. Our behavioural studies provide evidence that sexually mature male N. pompilius are attracted to females by excretions of the rectum.