|Budget Amount *help
¥1,600,000 (Direct Cost : ¥1,600,000)
Fiscal Year 2000 : ¥700,000 (Direct Cost : ¥700,000)
Fiscal Year 1999 : ¥900,000 (Direct Cost : ¥900,000)
Various chemical signals involved in larval metamorphosis and settlement of macrofouling organisms were examined for serpulid polychaete Hydroides ezoensis. We isolated and indentified a new monoacyl glycerol, 1-(4Z, 7Z, 10Z, 13Z, 16Z, 19Z)-docosahexaenoyl-glycerol as a metamorphosis inducing substance of larvae of H.ezoensis form MeOH extract of adult tube clumps of the same species. This result indicates that this substance attributes the gregarious settlement exhibited by this species. Various related compounds such as free fatty acids or their glycerids were also examined for their abilities to induce larval metamorphosis of H.ezoensis. In FFA's, only unsaturated FFA's induced larval metamorphosis and the metamorphosis-inducing activities depend on the presence and the number of unsaturated bonds of FFA's. Glycerids exhibited higher activities than FFA's.
Among artificial metamorphosis inducer, L-3,4-dihydroxyphenylalanine (L-DOPA) and neurotransmitter epinephrine induced larval metamorphosis in H.ezoensis.Enantiomer of L-DOPA, D-DOPA, which is inactive in vertebrates, also induced larval metamorphosis in lower degree. This result indicates the possibility that dopamine-receptor of different type from that of vertebrates may be involved in larval metamorphosis in H.ezoensis.Among several agonists of epinephrine tested, any specific agonists of α_1, α_2, or β type receptor exhibited clear results. This result indicates the possibility that adrenaline-receptor of different type from that of vertebrates may be involved in larval metamorphosis in H.ezoenssis.
Excess K^+ and Ca^<2+> ion in seawater also induced larval metamorphosis in dose dependently. Decrease of Ca^<2+> in seawater blocked the induction of larval metamorphosis by L-DOPA, indicating that induction of larval metamorphosis induced by excess Ca^<2+> may locate lower stream of cascades than that of L-DOPA.