Effect of size on reproductive output of giant crabs Pseudocarcinus gigas (Lamarck): Oziidae

Abstract

Fecundity and egg size of giant crabs (Pseudocarcinus gigas) were determined from egg masses of 162 crabs sampled from three sites in south-eastern Australia: western Victoria, western Tasmania and eastern Tasmania. Crabs ranged in carapace length from 126 to 220 mm and egg number ranged from 830000 to 2500000. Egg number and egg size increased with size of female. There appeared to be a decline in number of eggs and size of eggs with successive broods produced between moults. Sampling locality appeared to have little effect on reproductive output. Regression of an allometric model of log egg number to log crab size had a slope of 1.76 which was significantly less than 3.0. This indicates there is not a simple volumetric relationship between the variables, which would tend to occur if increasing fecundity with female size was a simple function of increased body space available for ovarian development. This pattern appeared to be a function of decreasing egg number and size with successive broods, and the trend of increasing egg size with female size.