Meeting Abstract

48.2  Jan. 6  Hot Flies: The Effects of Hypoxia on Thermal Tolerance in Drosophila melanogaster. LIGHTON, J.R.B.; UNLV and Sable Systems International lighton@sablesys.com

This study addresses the effects of acute hypoxia on thermal resistance in Drosophila. The upper critical thermal maximum (CT_max) of metazoans varies over a wide range, and its determinative factors, such as oxygen limitation, remain controversial. Induction of thermoprotective mechanisms after challenge by sublethal heat stress has been well documented in many organisms, including the model fly Drosophila melanogaster. Interestingly, however, other challenges � notably a period of anoxia � induce post-exposure thermoprotective effects in some organisms such as locusts. Here I show, using thermolimit respirometry, that acute hypoxia during thermal stress significantly reduces the CT_max of D. melanogaster, but only below an oxygen partial pressure of 10 kPa. Likewise, the scope for voluntary motor activity declines sharply below 10 kPa and is essentially eliminated at 2.5 kPa. Respiratory water loss increases highly significantly below 10 kPa. The post-mortal release of a large quantity of CO₂ is shown to be independent of loss of spiracular control, but dependent in part on oxygen availability. The results of this study are broadly in accord with the oxygen limitation hypothesis, but suggest that oxygen limitation only becomes an important factor during significant hypoxia.