Shell Utilization Pattern by the Hermit Crab Isocheles sawayai Forest and Saint Laurent, 1968 (Anomura, Diogenidae) from Margarita Island, Caribbean Sea, Venezuela

Abstract

Isocheles sawayai is a hermit crab that is occasionally mentioned in the literature, and recently its distribution was extended to Venezuelan waters. Because no information on the biology and shell use patterns of this species inhabiting Caribbean waters is available, we provide the first information on shell occupation patterns of I. sawayai from Venezuela. Specimens were collected monthly from January to December 2000 along the sandy shore of Margarita Island, Venezuela. The 942 specimens collected showed different shell use patterns between the sexes and according to the reproductive condition of the females. The gastropods Leucozonia nassa (37.37%), Engoniophos unicinctus (25.37%), Nassarius vibex (4.88%), Melongena melongena (4.25%), and Stramonita haemastoma (3.82%) represent 76% of the total occupied shells. Of the total of 26 different shell species occupied by I. sawayai, males were found occupying 21, while females were found occupying all 26 shell species. In general, both sexes most frequently occupied L. nassa and E. unicinctus. However, the percentage of females occupying these shells was significantly higher than that of the males. Regression analyses showed the best correlation between crab size, shell aperture width, and shell internal volume. The current comparative investigation, in combination with other South Atlantic populations of I. sawayai, provided further evidence of shell use adaptation in hermit crabs from different areas, and increases our insight into shell use of shallow-water hermit crabs.