Larval development ofPhyllaplysia tayloriDall, with a discussion of development in the anaspidea (opisthobranchiata: anaspidea)

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Abstract
The development of Phyllaplysia taylori Dall, an anaspid opisthobranch which occurs in the Zostera marina beds along the Pacific coast of North America, is described from development of the egg to post-metamorphosis and settlement. The developmental period within the capsule, approximately 30 days at 14.5 °C, ends with veliconch metamorphosis and direct settlement. The non-pelagic veliger simultaneously loses its velum and develops an active radula and meta- and pro-podium before hatching. Settlement immediately follows hatching and the veliconch takes up a crawling existence feeding on the substrate which may at first be the egg mass itself. Present also in the egg capsule during the entire developmental period is a spherical body, additional to the polar bodies, with a mean diameter of 49.2 µ Prior to loss of the velum this body is broken down by ciliary action and after development of the radula the particles are ingested as the pediveliger crawls in the capsule. After settlement, growth of the larval shell continues to form a visor-like hood up to 4 times the size of the larval shell. Of ten aplysiid species with known developmental type only P. taylori develops directly.