DISTRIBUTION, REPRODUCTION AND SHELL UTILIZATION PATTERNS IN 3 SPECIES OF INTERTIDAL HERMIT-CRABS ON A ROCKY SHORE ON THE PACIFIC COAST OF JAPAN

The spatial distribution, reproduction, and shell utilization patterns of three species of common intertidal hermit crabs Pagurus geminus McLaughlin, Pagurus lanuginosus De Haan and Clibanarius virescens (Krauss) on a rocky shore of Kominato, Bose Peninsula, Japan, are described. Although the distribution of each species greatly overlapped, Pagurus geminus mainly inhabited the middle intertidal zone, with Clibanarius virescens occupying a lower and Pagurus lanuginosus the lowest zone, This pattern was maintained over a 1-yr period with a few minor changes. Female Pagurus geminus generally inhabited a lower zone than males, ovigerous female Clibanarius virescens were distributed slightly lower than males, whereas a distinct sexual difference in the distribution was not seen in Pagurus lanuginosus. The ovigerous period of Pagurus geminus extended from October to August and is the longest reproductive season reported for a rocky intertidal decapod in Japanese waters. Pagurus lanuginosus became ovigerous from December to May and Clibanarius virescens, from April to December. The sex ratio was biased toward females in each case. Shell utilization patterns differed significantly between the three species, with Clibanarius virescens using the greatest variety of shells (33 species). Within species, sexual differences in shell utilization were seen in Pagurus geminus and Clibanarius vivescens.