SUMMARY

Variations in the concentration of calcium in the haemolymph and of total body calcium in Austropotamobius pallipes have been investigated. Haemolymph calcium concentration was independent of both body size and sex. During premoult the calcium concentration of the haemolymph rose from 11-8 ITIM/1 to 15-0 HIM/I. After the moult the calcium concentration remained high during stages A and B but declined to the intermoult level during stage C. Total body calcium was directly proportional to fresh body weight. No difference was apparent between calcium content of male and female crayfish of similar body weight