Asymmetrical morphology and growth of the hermit crab Pagurus filholi (Decapoda, Anomura, Paguridae) reared in non-dextral shell conditions

The body of a hermit crab shows asymmetrical morphology, which may be related to utilization of the dextral shell. To examine the effect of the shell, we reared Pagurus filholi (De Man, 1887) from the glaucothoe stage to full-sized adults, in a sinistral shell, in a straight tusk shell, without a shell, and in a normal dextral shell as a control. Body parts that show the most conspicuous asymmetry, uropods, pleopods and chelipeds, were checked at the time of the shedding of exuviae during rearing. No inversion of laterality on these characters was observed. However, in crabs subjected to conditions other than a dextral shell, the otherwise rather short right uropod became somewhat extended, and in those reared in sinistral shells, the right major cheliped was more enlarged.