Interactive effects of rearing temperature and oxygen on the development of Drosophila melanogaster

Although higher temperatures strongly stimulate ectothermic metabolic rates , they only slightly increase oxygen diffusion rates and decrease oxygen so lubility. Consequently, we predicted that insect gas exchange systems would have more difficulty meeting tissue oxygen demands at higher temperatures. In this study, Drosophila melanogaster were reared from egg to adult in hy peroxic (40%), hypoxic (10%), and normoxic (21%) conditions and in temperat ures ranging from 15 degrees -31.5 degreesC to examine the interactive effe ct of temperature and oxygen on development. Hyperoxia generally increased mass and growth rate at higher rearing temperatures. At lower rearing tempe ratures, however, hyperoxia had a very small effect on mass, did not affect growth rate, and lengthened time to eclosion. Relative to normoxia, flies reared in hypoxic conditions were generally smaller (mass and thorax length ), had longer eclosion times, slower growth rates, and reduced survival. At cooler temperatures, hypoxia had relatively modest or nonsignificant effec ts on development, while at higher temperatures, the effects of hypoxia wer e large. These results suggest that higher temperatures reduce oxygen deliv ery capacity relative to tissue oxygen needs, which may partially explain w hy ectotherms are smaller when development occurs at higher temperatures.