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Patterns of energy metabolism in the stone crab, Menippe mercenaria, during severe hypoxia and subsequent recovery.

Specimens of the stone crab, Menippe mercenaria, survived severe hypoxia (PO2 less than 8mm Hg) for at least 12 hr at 28-30 degrees C. During the time course of 12 hr of hypoxia, hemolymph L-lactate levels rose to 30-50 mumoles/g wet wt. There was a slight elevation of L-alanine levels, whereas succinate was found in only trace quantities in the hemolymph. Pronounced metabolic changes took place in the heart, cheliped closer, and leg socket muscles during severe hypoxia. L-lactate accumulated to levels ranging from 16-20 mumoles/g wet wt. There were pronounced changes in high-energy phosphate levels in the cheliped closer and leg socket muscles. Taking into account expected intra- and extracellular water content, the calculated intracellular lactate content in the three muscles investigated is substantially less than the hemolymph lactate concentrations. Part of this reverse concentration gradient may be accounted for by the reduction in lactate activity due to cation-lactate complex formation. Hemolymph calcium and magnesium concentrations rose considerably during severe hypoxia. During recovery from severe hypoxia, approximately 50% of the accumulated lactate in the hemolymph was cleared in 6 hr. Hemolymph lactate and alanine levels returned to near control levels after 24 hr of recovery. This study shows that the stone crab, M. mercenaria, survives severe hypoxia by a reliance on glycogen fermentation to lactate. This species is capable of tolerating high levels of accumulated lactate.