Metabolic function in Drosophila melanogaster in response to hypoxia and pure oxygen

This study examined the metabolic response of Drosophila melanogaster exposed to O-2 concentrations ranging from 0 to 21% and at 100%. The metabolic rate of flies exposed to graded hypoxia remained nearly constant as O-2 tensions were reduced from normoxia to similar to 3 kPa. There was a rapid, approximately linear reduction in fly metabolic rate at Po(2)s between 3 and 0.5kPa. The reduction in metabolic rate was especially pronounced at Po-2 levels <0.5 kPa, and at a Po-2 of 0.1 kPa fly metabolic rate was reduced similar to 10-fold relative to normoxic levels. The metabolic rate of flies exposed to anoxia and then returned to normoxia recovered to pre-anoxic levels within 30 min with no apparent payment of a hypoxia-induced oxygen debt. Flies tolerated exposure to hypoxia and/or anoxia for 40 min with nearly 100% survival. Fly mortality increased rapidly after 2h of anoxia and >16h exposure was uniformly lethal. Flies exposed to pure O-2 for 24 h showed no apparent alteration of metabolic rate, even though such O-2 tensions should damage respiratory enzymes critical to mitochondria function. Within a few hours the metabolic rate of flies recovering from exposure to repeated short bouts of anoxia was the same as flies exposed to a single anoxia exposure.