Control of ovarian rematuration in the yabby, Cherax destructor (Clark)

Postspawning rematuration studies were carried out in Cherax destructor. Rematuration did not occur whilst the female was still carrying eggs or neonates from the previous spawning, nor while the spent female was maintained in isolation under constant environmental conditions. Rematuration was triggered by a drop in temperature or by the presence of males. The influence of males was not mediated by water borne factors but was associated with either visual or tactile cues. Stimulation of ovarian growth by hormonal means could not be achieved. Release of endogenous ovary stimulating hormone was not induced by injections of serotonin. The extent of rematuration depended on the available energy reserves in the hepatopancreas. It was determined that if the hepatosomatic index was less than 7% the female would not re-spawn. The study suggests that an index of readiness to spawn (a Reproductive Condition Index) could be derived from the sum of hepatopancreas and ovarian weights.