Metabolic responses to anoxia and freezing by the freeze tolerant marine mussel Geukensia demissus
The effects of 2 or 12 h freezing at -6 °C or anoxia exposure at 5 °C on the metabolic responses of gill, mantle, adductor muscle, and hepatopancreas were characterized in the freeze tolerant, intertidal ribbed mussel Geukensia demissus (Dillwyn). In general, freezing and anoxia elicited different metabolic responses and these also differed in a tissue-specific manner. Fermentative end products accumulated in all tissues except gill under both stresses. In adductor muscle, lactate was produced in both cases. In mantle and hepatopancreas, only succinate accumulated in anoxia, correlated with an opposite decrease in aspartate, and changes in glycolytic intermediates were consistent with anoxia-induced metabolic arrest. During freezing, however, both lactate and succinate accumulated (as well as alanine in hepatopancreas) with net end product accumulation 3-4-fold greater than during anoxia and changes in glycolytic intermediates were consistent with the derivation of these products from carbohydrate catabolism. Other differences in response to freezing versus anoxia included the accumulation of glucose in all tissues and a reduction of energy charge in mantle during freezing, but not in anoxia. Taurine and glycine comprised about 80-85% of the total free amino acid pools in all tissues; in gill levels of both amino acids fell significantly during freezing or anoxia exposures whereas in mantle a significant decrease in these amino acids occurred during anoxia only. The data show both a broader range of metabolic responses, and greater net changes in metabolite levels during freezing compared with anoxia. This suggests (1) that metabolic responses to freezing include both cryoprotective and ischemia-protective changes, and (2) that tissue mechanisms of metabolic rate depression are rapidly induced during anoxia exposure but develop more slowly during freezing.
|Keywords||Anaerobiosis, Energetics, Freeze tolerance, Glycolytic regulation, Marine mollusc cold hardiness|
|Journal||Journal of Experimental Marine Biology and Ecology|
Storey, K, & Churchill, T.A. (Thomas A.). (1995). Metabolic responses to anoxia and freezing by the freeze tolerant marine mussel Geukensia demissus. Journal of Experimental Marine Biology and Ecology, 188(1), 99–114.