L-TRYPTOPHAN AND RELATED-COMPOUNDS INDUCE LARVAL SETTLEMENT OF THE BARNACLE BALANUS AMPHITRITE DARWIN

Effects of L-tryptophan and related compounds on larval settlement of barnacle Balanus amphitrite Darwin were examined. The settlement rate of young cyprids increased in proportion to L-tryptophan concentration (1.8 x 10(-5) M to 5.6 x 10(-4) M). The inducing effect of serotonin (5-hydroxytryptamine; 5-HT) on larval settlement was similar to that o f L-tryptophan at the concentration range of 3.4 x 10(-7) M to 1.1 x 1 0(-5) M. When 5-HT was applied to old cyprids, however, no inducing ef fect of larval settlement was observed. On the other hand, reserpin, a depleting agent of neuroactive amines such as 5-HT in mammals, showed inhibitory activity on settlement of old cyprids at the concentration of 10(-7) M.