Population consequences of shell utilization by hermit crabs.

The seashore hermit crabs (Clibanarius vittatus, Pagurus pollicaris and P. longicarpus have broadly overlapping shell utilization patterns along the Texas (USA) coast. Effects of shell stress resulting from this overlap and from an overall shortage of shells on the reproductive potentials of the crabs were examined. Regression analyses indicate that shell weight and internal volume affect the clutch sizes of C. vittatus and P. pollicaris but not P.longicarpus. G. vittatus maintained shells smaller than preferred grew more slowly than crabs maintained in shells of preferred size. Clutch size was highly correlated with crab size in this species. Several commensal animals, including polychaetes, gastropods, a hydroid and a xanthid crab, consumed hermit crab eggs and/or zoeae in the laboratory. These egg predators were encountered in large shells occupied by males more frequently than in shells in the size range utilized by ovigerous females. Shell size may limit hermit crab clutch size through a variety of mechanisms.