Observations on development,larval growth and metamorphosis of four species of aplysiidae (gastropoda: Opisthobranchia) in laboratory culture

The development of simple, reliable techniques for the laboratory culture of aplysiid gastropods through their complete life cycle, has enabled us to study the larval biology, metamorphosis, and early juvenile development of these animals. Egg masses, duration of the embryonic phase, veligers, and larval growth and development are described for four species of Hawaiian Aplysiidae, namely, Aplysia dactylomela Rang, Aplysia Juliana Quoy and Gaimard, Dolabella auricularia (Lightfoot) and Stylocheilus longicauda (Quoy and Gaimard). Metamorphosis and early juvenile development of A. Juliana are described in detail with additional comments on these processes in the other three species. Length of the embryonic phase and size of the veliger at hatching are a function of the size of the uncleaved egg. All four species develop planktotrophically and have ≈ 30-day larval phases. In each species the larval phase includes a period of rapid shell growth to a species-specific size followed by a non-growth period during which other morphological developments occur to culminate in metamorphic competence. The larvae of each species metamorphose preferentially on a particular species of benthic algae. The events of metamorphosis require 2 to 4 days for completion and transform the planktonic filter-feeding larva into a benthic, radular-feeding juvenile. Postlarval development includes growth of the shell, parapodia, oral tentacles, rhinophores, anal siphon, and structures of the mantle cavity.