Effects of Oxygen Deprivation on Aquatic Midge Larvae under Natural and Laboratory Conditions

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Abstract
Larvae of 2 species of Chironomus were maintained under controlled conditions, using asbestos wool as a burrowing material. Starved larvae in oxygen-saturated water lost 0.56% of their dry weight in glycogen per day. At similar temperatures, larvae in oxygen-free water lost 0.96% per day. There was a significant positive correlation between temperature and the rate of loss under nitrogen. The glycogen content of larvae with access to food but not oxygen was significantly lower than that of similar larvae without oxygen. Glycogen made up 13-14% of the dry body weight of 3 species of Chlronomue which tolerate anoxia to some extent. It composed 2% of the larvae of the intolerant Tanytarsus sp. The glycogen content of larvae of C. plumosus declines significantly under prolonged anoxia in the hypolimnion of Lake Mendota. It does not change significantly in the oxygenated epilimnion or in the unstratified Lake Wingra. The content rises slowly after oxygen is restored to the former animals. The C. plumosus larvae accumulate lactic acid for several days after oxygen is removed from their environment but retard the rate of accumulation or reduce the amount present thereafter. No effects of anoxia on the behavior of the larvae were noted in the laboratory, but those collected from Lake Mendota after long exposure were motionless.