Organ-specific metabolism during anoxia and recovery from anoxia in the cherrystone clam, Mercenaria mercenaria

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Abstract
The levels of intermediary metabolites and end products were quantified in the tissues of the cherrystone clam, Mercenaria mercenaria, over a time course of 96 h of anoxia followed by 48 h of aerobic recovery. Succinate and alanine accumulated as anaerobic products while glycogen and aspartate were utilized as substrates. Succinate accumulation ranged from 12–14 μmol/g wet weight in muscle (phasic and catch adductor, foot) to 25 μmol/g in gill and mantle with 32 μmol/mL released into the mantle cavity fluid. Lesser amounts of alanine were produced, the ratio succinate:alanine varying from 1.4:1 in phasic adductor to 3.2:1 in mantle at 96 h. Aspartate reserves apparently supply the carbon for succinate synthesis over the first 6–12 h of anoxia; subsequent succinate and alanine production probably results from glycogen fermentation. The imino acids alanopine and strombine were not produced in appreciable amounts (<1 μmol/g) during anoxia. When returned to aerated seawater, control levels of alanine and aspartate were reestablished within 24 h; accumulated succinate was catabolized within 48 h. Glycogen content of all tissues showed a sharp decline after 6 h of recovery, perhaps due to enhanced energy demands, but levels increased later in recovery. Tissue ATP levels, which were depressed during anoxia, were restored by 24 h.

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