Anaerobic metabolism in aquatic insect larvae: studies onChironomus thummi andCulex pipiens

Summary The metabolic effect of hypoxia and anoxia on the larvae ofChironomus thummi andCulex pipiens was investigated. InC. thummi anoxia resulted in a characteristic decrease of ATP and P-arginine concentrations and in an accumulation of alanine and lactate within 60 minutes. These changes continued during prolonged incubation but at lower rates. Ethanol, the major product during long-term anoxia, was largely excreted into the ambient water.A significant accumulation of these metabolites occurred only at a of 7 Torr. However, the proportion of anaerobic energy production even at this low amounted to less than 5% of the total energy consumption measured during experimental anoxia. Thus the chironomid larvae exhibited a remarkable capacity for utilizing very low levels of oxygen to maintain an aerobic metabolism. Complete anaerobiosis was observed only under anoxic conditions.Recovery from prior anoxia began with the reestablishment of normal ATP, P-arginine and succinate concentrations, whereas removal of the accumulated alanine and lactate and replenishment of the normally high level of malate required several hours.Culex larvae were shown to have a very low anaerobic capacity and a high rate of lactate accumulation.The significance of the results is discussed with particular emphasis on comparative aspects.