LARVAL STRATEGIES OF NUDIBRANCH MOLLUSKS - SIMILAR MEANS TO THE SAME END

Growth, development and metamorphosis of the planktotrophic larvae of Onchidoris bilamellata (L.) were followed in the laboratory at a range of culture temperatures and on a variety of microalgal diets. Successful culture of the nudibranch larvae at 5-degrees-C (approximating field temperatures) indicated developmental periods in agreement with previous estimations. Thus, predictions of the coincident timing of settlement and metamorphosis of O. bilamellata and the prey (Semibalanus balanoides (L.)) barnacles in the field are upheld. In this respect Todd & Doyle's (1981) "settlement-timing" hypothesis-as an explanation for the observed larval strategy of O. bilamellata-appears tenable. However, juveniles were observed to subsist on detritus for several weeks prior to their ability to prey upon S. balanoides. This precludes the validity of inferring a close matching of predator and prey settlement in explaining the specific larval strategy. In the light of other published data on larval/post-larval development, growth and feeding an alternative hypothesis, concerned with selective 'opportunities' in the evolution of nudibranch larval strategies, is outlined.