Settlement behavior of cyphonautes larvae of the bryozoan Membranipora membranacea in response to two algal substrata

Settlement is an important process in the biphasic life histories of many marine invertebrates. Little is known regarding the fine-scale behavioral mechanisms for finding and attaching to a suitable substratum, particularly under conditions that may impose a potential challenge, such as flow. In this study, we examined the settlement behavior of cyphonautes larvae of the bryozoan, Membranipora membranacea, in response to two different algal substrata. Larvae showed a strong preference for settling on the kelp Nereocystis luetkeana over the red alga Mazzaella splendens. We then tested whether the behavioral mechanisms used by larvae to attach to these algae differed when presented with the challenge of flowing water during settlement. We found that larvae exhibited different behaviors on the two species of algae in flowing water. Larvae were more often observed in direct contact with the preferred alga (N. luetkeana) exhibiting fine-scale active search behaviors. On the less preferred alga (M. splendens), larvae were less frequently observed in direct contact with the alga, and appeared to be exhibiting broad-scale passive search behaviors along the surface of the blade. Our results suggest that cyphonautes larvae alter their behavior in response to their preferred settlement habitat.