Roles of dopamine and serotonin in larval attachment of the barnacle, Balanus amphitrite.

In order to clarify the roles of neurotransmitters including serotonin and dopamine in larval settlement (attachment) and metamorphosis of the barnacle Balanus amphitrite, the effects of lisuride, which acts as both a serotonin agonist/antagonist and a dopamine agonist, were examined. Lisuride did not induce larval attachment and metamorphosis; however, it promoted only larval behavior of searching for attachment sites without actual attachment to substrata which lasted for 5 to 6 days in a dose-dependent manner. Further evidence was obtained with a range of agonists/antagonists; serotonin agonists promoted the attachment, while serotonin antagonists inhibited it. Similarly, dopamine agonists inhibited the attachment. Furthermore, mixtures of serotonin and dopamine showed similar effects to those of lisuride. These results suggested that the promotion effect on larval searching behavior was derived from a combination of activities of serotonin and dopamine. Moreover, both serotonin and dopamine were detected in cyprids by HPLC. Thus, larval attachment process is regulated by both serotonin and dopamine neurons in this species. J. Exp. Zool. 284:746-758, 1999. Copyright 1999 Wiley-Liss, Inc.