Net uptake of calcium by Austropotamobius begins 15-30 min after the moult and rapidly reaches a maximum level (2 µmoles/g/h at 10°C) which is maintained throughout stages A and B. At stage C1 the rate of net uptake falls sharply to a lower level which is gradually reduced until equilibrium is reached at C4. The uptake mechanism is near-saturated at 0.4 mM-Ca/l and half-saturated at 0.13 mM-Ca/l. In the absence of external HCO3- net uptake is reduced. Calcium uptake is against an electrochemical gradient. The concentration of ionised calcium in the haemolymph remains unchanged during the intermoult cycle.

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