The role of chemical signals in the spawning induction of polychaete worms and other marine invertebrates

Extracts of gonad, body fluid and spawning water (into which gametes have been released by the process of spawning) were tested for the presence of spawning-inducing activity (SIA) on both sexes of the polychaetes Nereis succinea (Frey and Leuckhart) and Platynereis dumerilii (Audouin and Milne-Edwards). Gonadal and body fluid extracts from Asterias rubens (L.) and Echinus esculentus (L.) (echinoderms), Arenicola marina (L.) (polychaete), Clupea harengus (L.) (teleost) and body fluid and spawning water of Nereis virens (Sars) (polychaete) all exhibit SIA on male N. succinea. C. harengus extract from male gonads also had SIA on male P. dumerilii. Phytoplankton monoculture extracts were also tested. The cryptomonad (Rhodomonas baltica) (Karsten) had SIA on male P. dumerilii, and the diatom Phaeodactylum tricornutum (Bohlin) had some activity on Mytilus edulis (L.). The active fraction of R. baltica is chromatographically similar to uric acid (the natural sperm-release pheromone produced by females of P. dumerilii) [Nature 382 (1996) 214], but has a different retention time and UV absorbance spectra on reverse phase HPLC. Conspecific extracts of spawning water and gonadal material did not have SIA on the same and opposite sex in A. marina and N. virens. The role of chemical signals in marine invertebrates is discussed in relation to their mode of spawning.