The effects of carbon dioxide anesthesia and anoxia on rapid cold-hardening and chill coma recovery in Drosophila melanogaster

Abstract

Carbon dioxide gas is used as an insect anesthetic in many laboratories, despite recent studies which have shown that CO 2 can alter behavior and fitness. We examine the effects of CO 2 and anoxia (N 2) on cold tolerance, measuring the rapid cold-hardening (RCH) response and chill coma recovery in Drosophila melanogaster. Short exposures to CO 2 or N 2 do not significantly affect RCH, but 60 min of exposure negates RCH. Exposure to CO 2 anesthesia increases chill coma recovery time, but this effect disappears if the flies are given 90 min recovery in air before chill coma induction. Flies treated with N 2 show a similar pattern, but require significantly longer chill coma recovery times even after 90 min of recovery from anoxia. Our results suggest that CO 2 anesthesia is an acceptable way to manipulate flies before cold tolerance experiments (when using RCH or chill coma recovery as a measure), provided exposure duration is minimized and recovery is permitted before chill coma induction. However, we recommend that exposure to N 2 not be used as a method of anesthesia for chill coma studies.