(full paper is archived in the Miller Library)
Title: The behavior, distribution and life cycle of the pea crab Pinnotheres pugettensis in relation to its ascidian host Styela montereyensis
Student Author(s): Peters, Richard
Faculty Advisor(s): Abbott, Donald P.
Location: Final Papers Biology 175H
Date: June 1980
Keywords: symbiosis at the seashore
Abstract: The commensal pea crab Pinnotheres pugettensis inhabits about 33% of the subtidal population of its ascidian host, Stylea montereyensis, in southern Monterey Bay, California. No pea crabs were found in intertidal S. montereyensis. Of 247 tunicates dissected 62 contained one crab, four held two crabs and one tunicate contained three crabs. There was never more than one adult female P. pugettensis per tunicate. The crabs live in the anterior third of the atrial cavity of the tunicate, and feed by reaching into the pharyngeal cavity, through a small well-healed hole situated dorsally in the pharyngeal wall, and taking pieces of the rope of mucus and trapped food particles rolled up by the ascidian dorsal lamina. We saw no evidence of filter feeding by adult P. pugettensis. Eggs hatch as advanced zoeae, which molt to a second zoeal stage in 10-12 days, to a megalops at 20-24 days, and to the first juvenile instar at 28-30 days. Adult males are dark brown and hard shelled, and generally smaller than the translucent and soft shelled adult females.