Effect of air exposure on nitrogen metabolism in the crab Cancer pagurus

In C. pagurus exposed to air for 18 h, blood ammonia content decreased within the 2 first hours, then increased at a relatively constant rate (25 microM/h); blood urate content increased at a lower rate (10 microM/h) and a classical blood acidosis was observed. In the cheliped muscle, a transient 22% decrease in GDH activity for ammonia formation and a 48% increase in GDH activity in the reverse reaction (glutamate synthesis) occurred following 6 and 12 h of emersion, respectively. Changes in LDH activity, used as an indicator of anaerobic potential of muscle, were not observed, except for an 18% increase in crabs exposed to air for 24 h. The increase in blood urate content, not known as a response to emersion in decapods, appeared to be different from that observed in response to hypoxia. The relatively low blood ammonia overload and the GDH increased activity for glutamate synthesis suggested that part of the produced ammonia was stored under a bound form in some tissues. The response of C. pagurus to air exposure is discussed on account of the Storey and Storey ('90) theory.