CHEMICAL LANGUAGES IN LARVAL SETTLEMENT O F MARINE ORGANISMS - SETTLEMENT INHIBITING SUBSTANCES AGAINST BARNACLES, AND SETTLEMENT INDUCING SUBSTANCES IN ASCIDIANS

For understanding the interactions between marine organisms, me focuse d on larval settlement (attachment and metamorphosis) of sessile marin e organisms, where chemical substances (chemical signals) play importa nt roles. Here we report firstly the settlement inhibiting substances against barnacles (Balanus amphitrite). More than 300 marine invertebr ates were screened for antifouling activity, and more than 60 antifoul ing compounds including almost 30 new ones were obtained. Some of thes e compounds [especially with isocyanide, isothiocyanate, and/or formam ide group(s)] show strong antifouling activity without toxicity at the very low concentrations. Secondly, we report the metamorphosis induci ng substances for ascidians (mainly Halocynthia roretzi). Almost 40 co mpounds which induce/promote larval metamorphosis were obtained from m arine organisms. The real cue for metamorphosis has been isolated from conspecific conditioned water and identified as lumichrome.