Shelter use by Calcinus verrilli, Bermuda's endemic hermit crab

grantor: University of Toronto'Calcinus verrilli', a hermit crab endemic to Bermuda, is unusual in that it inhabits both gastropod shells ('Cerithium litteratum ') and gastropod tubes ('Dendropoma irregulare' and ' Dendropoma annulatus'; 'Vermicularia knorrii' and ' Vermicularia spirata'). Field surveys found significantly more males inhabiting shells and significantly more females inhabiting tubes. In the laboratory no significant difference was shown in shelter choice for males or females. In a second choice experiment, males showed no discrimination between gastropod extract types, and females showed discrimination that related to the shelter they were collected in. In a competition between the sexes, the winner of the intact shell was found to depend upon relative shield length and relative major chela length. Overall, males were found to be better exploitative competitors than females. A significant difference in uropod asymmetry was found; tube dwellers were more symmetrical than shell dwellers. A shelter manipulation experiment found shelter type to be important in determining asymmetry. The distribution of 'C. verrilli' between shells and tubes may be an example of "making the best of a bad situation," if 'Polydora' sp. is detrimental to the reproductive success of the hermit crab.M.Sc