Abstracts Biological Sciences

The larval histories of four porcellanid anomurans (Crustacea, Decapoda) from Oregon

by Sue Lewayne Gonor

Complete larval histories, consisting of a prezoeal stage, two zoeal stages and one megalopal stage,are described for four species of porcellanid anomurans. Larvae of three species were reared from embryos through the megalopa stage in the laboratory. Larvae of the fourth species were collected from the plankton and reared to subsequent stages in the laboratory. The identity of these larvae was verified on the basis of prezoeae and subsequent zoeae released from a single female in the laboratory. Various combinations of salinity and temperature were used in cultures to determine "ideal" levels of these physical factors for larval rearing in the laboratory. This revealed two points; the larvae are viable in the laboratory only under conditions of high salinity, and temperature distinctly influences viability and rate of larval development. Throughout the rearing experiments observations were made on four aspects of larval behavior, Basic respiratory movements were found to be similar in prezoeal and zoeal stages becoming only slightly more complex in the megalopa larva, Cleaning behavior, unobserved in prezoeae, was simple in the zoeal stages and became exceedlingly complex in the megalopa stage. Feeding habits and diet ranged from nonexistence in the prezoea to carnivorous in both zoeal stages and climaxed in the megalopa with herbivorous filter feeding. Locomotory behavior showed a similar pattern of increasing complexity beginning with sporadic abdominal flexion in the prezoea, progres sing to maxilliped swimming in the zoeal stages and climaxing in the megalopa larva with pleopodal swimming, pereiopodal walking and later swimming by abdominal clapping. Species studied here include Pachycheles rudis, Pachycheles pubescens, Petrolisthes eriomerus, and Petrolisthes cinctipes.