The effect of anesthesia on the photoresponses of four sympatric species of Drosophila.

Five isofemale strains from each of four sympatric species, Drosophila immigrans, D. repleta, D. melanogaster, and D. affinis, were lightly anesthetized with ether, CO2, Flynap, or cold temperature. The photoresponse of each treatment group was measured in an open field and a Y-tube apparatus. Relative light values were compared with those of the unanesthetized control groups of each species, as well as among the different treatments themselves and among species. Significant differences between species were apparent for all treatments in the Y-tube and for all treatments except ether and CO2 in the open field. Response to anesthesia may differ between species due, in part, to their differing genotypes. Comparing treatment groups within species in the Y-tube design, all species except D. melanogaster showed significant differences between treatments. In the open field, only D. affinis was significantly affected. Particularly in the Y-tube, anesthetized flies generally differed significantly from the controls, indicating that the use of anesthesia during a behavioral study could cause deviations in behavior from that of normal unanesthetized flies.