Strategies of anaerobiosis in New Zealand infaunal bivalves: Adaptations to environmental and functional hypoxia

Abstract

Under hypoxic environmental conditions, slowly burrowing bivalves such as the pipi (Paphies australis) and cockle (Austrovenus stutchburyi) support anaerobic energy production through the pyruvate reductase enzymes strombine dehydro-genase and alanopine dehydrogenase. Rapidly digging surf clams such as the tuatua (P. sub-triangulatum) and trough shell (Mactra discors) do not fare as well at low oxygen levels, but perform better under the functional anaerobiosis generated by burrowing, and energy production is supported by octopine dehydrogenase. Muscle buffering capacity is higher in rapidly burrowing species and is correlated with total pyruvate reductase activity. Anaerobic pathways in P. subtriangulatum led to both D-lactate and octopine accumulation during environmental hypoxia, but only octopine accumulated during burrowing. Bivalves adapted to environmental hypoxia maintained high adenylate energy charge (AEC) under anaerobiosis, indicating a close matching of ATP production to consumption. AEC fell in P. subtriangulatum during environmental hypoxia. The significance of these findings is discussed within an ecological context, and in relation to the storage of live clams for the seafood industry. © The Royal Society of New Zealand 1995.