ACCLIMATIZATION TO INTERTIDAL CONDITIONS MODIFIES THE PHYSIOLOGICAL-RESPONSE TO PROLONGED AIR EXPOSURE IN MYTILUS-EDULIS

Both the tolerance of air exposure and the metabolic means by which mussels, Mytilus edulis, face air exposure can be modified by intertidal acclimatization. Short-term intertidal acclimatization enhanced the tolerance of air exposure most in early summer. Prevention of air breathing increased the mortality of wild and non-acclimatized cultured (i.e., control) mussels, but only slightly enhanced that of intertidally acclimatized mussels, suggesting their increased dependence upon anaerobic metabolism. In June, anaerobic end products accumulated in the adductor muscle of cultured but not of wild mussels. Intertidal acclimatization shifted the pattern and rates of metabolite accumulation. Control mussels accumulated succinate and alanine in the adductor muscle while intertidally acclimatized mussels accumulated strombine + alanopine, albeit at far lower levels. Pyruvate kinase (PK) from adductor muscle of intertidally acclimatized mussels was gradually activated during prolonged air exposure, while that of control and wild mussels was more inhibited. In July and August, during prolonged air exposure, the PK from the most viable mussels generally was the most inhibited. Prevention of air breathing did not markedly change the time course of PK inhibition during air exposure. Cultured mussels used in the present study were obtained from growers in Quebec, and wild mussels were collected from the Baie des Chaleurs (Quebec, PQ) in 1988.