Shell-Exchange Behavior in a Hermit-Crab-Like Tanaidacean (Crustacea: Malacostraca)

This study describes shell-exchange behavior in the hermit-crab-like tanaidacean Macrolabrum sp. (Pagurapseudidae: Pagurapseudinae) under captive conditions. I observed one shell exchange by Macrolabrum sp., the behavioral sequence of which was as follows: a shell-carrying tanaidacean 1) grasped the edge of the aperture of an empty gastropod shell with its right cheliped; 2) inspected the condition inside the shell four times by inserting the anterior portion of its body into the shell; and 3) moved into the shell, posterior end (pleotelson) first. The elapsed time from the initial grasping of the empty shell to completing the move into it was 2 min 20 sec. In contrast to a Pagurapseudes tanaidacean and hermit crabs, the individual of Macrolabrum sp. did not examine the external surface of the shell during the single shell exchange observed.