Coral preference behaviour by planktotrophic larvae of Spirobranchus giganteus corniculatus (Serpulidae: Polychaeta)

Abstract

Planktonic larvae of the serpulid polychaete Spirobranchus giganteus, an obligate associate of live coral, were tested for preferences for materials diffusing from natural substrates. Choices offered were Acropora prolifera, a very abundant coral on the Heron Island reef flat; Palauastraea ramosa, a less abundant coral, dead coral rubble and a glass tube as a control. Larval life is approximately 12 days. The larvae tested were 1–4 days old. Adults of S. giganteus occur commonly on A. prolifera and much less frequently on P. ramosa. Experiments were designed to prevent contact between larvae and substrate. Larvae preferred A. prolifera over P. ramosa, rubble and the control. There was no preference expressed between the control and P. ramosa or the control and rubble. A preference by young S. giganteus larvae for a substance diffusing from coral, acting together with a known positive phototaxis, may be adaptive in that it may help to maintain larvae in surface waters over the reef and in the vicinity of a specific coral until they are old enough to settle.