OXYGEN CONSUMPTION AND VENTILATION IN DECLINING OXYGEN TENSION AND POSTHYPOXIC RECOVERY IN EPIGEAN AND HYPOGEAN CRUSTACEANS

Abstract

ABSTRACT Respiratory and ventilatory responses to declining O2 tension and posthypoxic recovery were investigated in 3 hypogean and in 2 epigean aquatic crustaceans. The aims of this study were to determine how these species reacted to declining O2 tension, to investigate their changes in ventilation and metabolic rate during progressive hypoxia, and to extend our knowledge on the fate of anaerobic end products during subsequent recovery. Hypogean organisms had normoxic O2 consumption rates 1.7―3.5 times lower than the epigean species. All 5 crustaceans were able to maintain their O2 consumption rates (1) at relatively constant levels and (2) independent of Po2 between normoxia and the critical Po2. Hypogean species also possessed lower critical Po2 than epigean ones, which may indicate that these organisms are better adapted to low O2 content and are better equipped to stay aerobic under hypoxia. For all species, posthypoxic recovery resulted in a high O2 debt. The payment of this debt was smaller in hypogean than in epigean species. The main explanations of the lower 0, debt shown by hypogean organisms are the lower energetic expenditures noticed during hypoxia, partly due to a decrease in locomotory and ventilatory activities.