Paradoxical effect of serotonin on ciliary locomotion of the adult archiannelid worms Dinophilus gyrociliatus and D. Taeniatus (annelida: Polychaeta)

Abstract

Immunochemical detection of serotonin (5-HT) and tubulin in D. gyrociliatus and D. taeniatus revealed similar anatomical structures of ventral locomotory ciliary field and underlying 5-HT-immunoreactive nerve network in both young juvenile and adult worms. External application of 5-HT and serotonin biochemical precursor (5-HTP) resulted in increased level of 5-HT within nervous structures in both juveniles and adults. However, while 5-HT and 5-HTP increased speed of gliding locomotion in juvenile worms, the same concentration of drugs decreased significantly or did not affect locomotion of adults. Thus, 5-HT activates the gliding locomotion in juvenile Archiannelid worms similar to larvae of annelids, molluscs and flatworms which use cilia for locomotion. Altered mode of 5-HT action on the locomotion of adult Archiannelid worms indicates reorganization of the 5-HT cilia controlling system during Dinophilid maturation.