REPRODUCTIVE INVESTMENT IN 2 SPIDER CRABS WITH DIFFERENT BREEDING STRATEGIES

Reproductive investment was studied in Irish Sea populations of the sp ider crabs Hyas coarctatus and Inachus dorsettensis. The species are s imilar in that reproduction is restricted to the terminal instar, but differ in that H. coarctatus produces a single brood per year, whilst I. dorsettensis produces several. In relation to body weight, egg numb er (and brood weight) was higher in H. coarctatus. In I. dorsettensis, the first brood produced after maturity had a much lower egg number t han subsequent broods. Energy content of broods in relation to energy content of females displayed similar trends, with means of 35 and 32% in Hyas and Inachus, respectively. However, the annual investment in r eproduction was higher in Inachus. Possible explanations for an appare ntly suboptimal reproductive strategy in Hyas are discussed.