Investigations into the Settlement and Attachment of Biofouling Marine Invertebrates

Abstract

Abstract : Bugula neritina is a sessile marine bryozoan with a pelagic larval stage. Larvae frequently settle on boat hulls, facilitating the introduction of . neritina to bays and estuaries worldwide. Adrenergic agonists, such as noradrenaline, inhibit larval settlement in a variety of marine invertebrate species, including B. neritina. Light also inhibits B. neritina larval settlement, yet the underlying mechanisms by which light and adrenergic compounds exert their effects on larvae are largely unknown. Octopamine is considered the invertebrate analog of noradrenaline, and may be involved in larval settlement pathways. In this study, we observed the effects of noradrenaline and the adrenergic antagonist phentolamine on larval settlement, and found that high concentrations of noradrenaline inhibited larval attachment and increased larval swimming behavior. High concentrations of phentolamine increased larval attachment and decreased larval swimming behavior. We used fluorescent labeling and microscopy to localize sensory system components, and found that larvae possess adrenergic-like receptors and octopamine-like immunoreactivity. We also exposed larvae to phentolamine in both dark and light conditions, and found that light inhibited larval attachment, but phentolamine blocked those inhibitory effects. Based on these results, we put forth putative sensory pathway that explains the effects of both light and adrenergic compounds on B. neritina larval settlement behavior. This study sheds light on previously unknown larval sensory mechanisms and may aid in the development of effective, non-toxic biofouling control strategies.