Calcium balance at the premoult stage of the freshwater crayfish Austropotamobus pallipes (Lereboullet).

The premoult stage in Austropotamobtus pallipes is characterized by a net loss of calcium which increases from Do to a maximum of 0-83 /imoles/g/h at D4. The concentration of ionized calcium in the haemolymph does not increase during the premoult stage although there is an increase in complexed calcium. The electrochemical gradient across the body surface is similar to that at the intermoult stage and favours calcium outflux. Possible routes for calcium net loss have been discussed and a mechanism for elimination of calcium has been proposed.