Meeting Abstract

P1-49   -   Settlement preferences and post-settlement cannibalism in the sea star Asterias forbesi Davis, ARK*; McAlister, JS; Allen, JD; William and Mary, Williamsburg, VA; College of the Holy Cross, Worcester, MA; William and Mary, Williamsburg, VA arkalytiakdavi@email.wm.edu

Many marine invertebrates exhibit a biphasic life history; fertilization and larval development occur in the plankton, while juveniles and adults inhabit the benthos. The shift from the plankton to the benthos involves attachment to a substrate by a competent larva, metamorphosis, and subsequent survival on the benthos as a microscopic juvenile. The transition from larva to juvenile and the immediate post-settlement period is difficult to study in the field and its ecology is poorly understood. We performed experiments to assess the larval settlement preferences the sea star Asterias forbesi and found competent A. forbesi larvae exhibited strong substrate specificity. Shells of the blue mussel, Mytilus edulis, were most preferred, though settlement was also evident on encrusting coralline algae and Irish sea moss. Little settlement occurred on biofouled rocks, and none was observed when no cue was given. Interestingly, larvae readily settled on the shells of dead M. edulis, but avoided settling on live juvenile mussels, a potential food source. Patterns of post-settlement cannibalism were also examined. Recently settled, relatively large, A. forbesi were provided smaller juveniles of two types, distinguished by fluorochrome staining. In one set of experiments, focal A. forbesi selected between siblings and unrelated juveniles. In other trials, focal juveniles were offered a choice between unrelated juvenile conspecifics and congeners of Asterias rubens. Within species, cannibalism was not affected by relatedness, but A. forbesi demonstrated a preference to cannibalize A. rubens over conspecifics. Our results indicate that larval A. forbesi strongly prefer to settle on available M. edulis, and that this specific settlement preference may facilitate high rates of cannibalism in high recruitment years.