Sex Ratio as a Function of Size in Hippa pacifica Dana (Crustacea, Anomura, Hippidae): A Test of the Sex Reversal and Differential Growth Rate Hypotheses

Abstract

Sex ratio as a function of size was examined for the Pacific mole crab, Hippa pacifica Dana. A majority of small animals are male, a larger majority of intermediate sizes are male, and all large animals are female. Sex reversal and differential growth rate were tested as hypotheses to explain this pattern of size-related sex ratio. Rearing of males and histological examination of gonads provided no evidence in support of sex reversal. Female crabs molt more often than do males, and have larger molt increments. These two factors can account for the sex ratio pattern observed.