Meeting Abstract

P2.2  Sunday, Jan. 5 15:30  The hairy hermit crab, Pagurus hirsutiusculus, differs from other species of intertidal hermit crabs in shell selection, escape behavior, and reactions to predators CHAVEZ, S.D.*; MERZ, R.A.; Cerritos College, Norwalk, California; Swarthmore College, Pennsylvania samicat11@gmail.com

Intertidal hermit crabs of Puget Sound include Pagurus hirsutiusculus, P. granosimanus, and P. beringanus. Both P. granosimanus and P. beringanus individuals were found in shells about four times their body weight while P. hirsutiusculus were typically in shells slightly lighter than body weight; except for gravid females that carried shells nearly twice their body weight. Unlike P. granosimanus and P. beringanus, which always retreat into their shells when picked up, 73% of P. hirsutiusculus (n=126) abandon their shells. Gravid female P. hirsutiusculus were less likely to display this behavior – only about 23% abandoned their shells. P. hirsutiusculus is an especially active hermit crab; after being startled by a controlled thump on its holding tank a crab would recover normal behavior in about 6 sec.; P. granosimanus took twice as long. When placed in water that had previously contained rapidly moving, visual and chemosensitive predators (either Cancer productus or C. magister), P. hirsutiusculus displayed the same or a slower recovery from the startle stimulus while the behavior of P. granosimanus remained unchanged and relatively slow. In contrast, hermit crabs exposed to water that had contained the slow moving, chemosensitive predatory starfish Pycnopodia helianthoides either retained their high recovery rate (P. hirsutiusculus) or increased it (P. granosimanus). These findings suggest that P. hirsutiusculus is a “shell minimalist” selecting small, relatively lighter shells that it readily abandons, relying on quick escape behavior in the presence of slow moving predators. These behaviors are modified in gravid females or in the presence of rapidly moving visual predators.