Tactile Stimuli in the Social Behavior of Pagurus Bernhard Us (Decapoda, Paguridae)

Abstract

A series of social behavior patterns of the hermit crab Pagurus bernhardus were examined to determine the adequate stimuli for the acts. (1) Cheliped flicking, a rapid out-in movement of one or both cheliped mani, is elicited by touch on any part of the appendages exposed when a crab withdraws into its shell. Execution of flicks is inhibited both by general photic input and by a specific type of visual input (sight of a very large crab) just before ducking in its shell. (2) Dislodging-shaking, a rapid movement up and down of the whole body-shell, is elicited by placement of weight almost anywhere on the back of a crab's gastropod shell. The adequate weight is larger for larger crabs and larger for a given size crab in a heavier shell. (3) Shell fighting behavior is likely when a crab is in a shell that is either too small (in volume) or too large (in weight). Recently moulted crabs more readily lose shell fights and smaller crabs almost never win shell fights against larger crabs. (4) Male P. bernhardus can be sexually excited by contact with the exoskeleton of recently courted females. The stimulus may be chemo-tactic in nature.