Settlement of the barnacle Balanus improvisus: the roles of dopamine and serotonin

The regulation of the settlement process in barnacles has attracted research interest due to their role as fouling organisms. The involvement of neurotransmitters in the regulation of settlement of marine invertebrate larvae has been described in several species. In this work, we reported the effects of the neurotransmitters dopamine and serotonin on the settlement of cyprids of the barnacle Balanus improvisus and described differences among cyprids of different ages. Also, we tested the effects of dopaminergic and serotonergic agonists and antagonists on settlement of cyprid larvae. We found that dopamine significantly stimulated settlement of 2- and 4-day-old cyprids, while serotonin exerted an inhibitory effect, regardless of cyprid age. The agonists and antagonists to the two neurotransmitters were not able to stimulate settlement but in general had either an inhibitory or no effect. We compared our results to those previously reported of the roles of dopamine and serotonin in the settlement of Balanus amphitrite. There appeared to be striking differences in the effects of these neurotransmitters between the two species because it has been reported that serotonin induces settlement in B. amphitrite and that dopamine inhibits it. This suggested that dopamine and serotonin play pivotal roles in settlement of barnacle but may act in different ways in the two species.