Experimental evolution of response to anoxia in : recovery of locomotion following CO or N exposure.

Many insects enter coma upon exposure to anoxia, a feature routinely exploited by experimentalists to handle them. But the genetic and physiological bases of anoxic coma induction and recovery are only partially understood, as are the long-term consequences for the animal's performance. We examined three populations of (designated B) that have been inadvertently under selection for rapid recovery from CO exposure for nearly 40 years (around 1000 generations) resulting from routine maintenance practices. We contrasted CO and N (presumed a less reactive gas) knockdown and recovery times of these B flies with six populations of common ancestry (A and C populations) that were not exposed to CO over the same period. We found that B populations showed faster and more consistent locomotor recovery than A or C populations after CO knockdown, a result also observed with N knockdown. A and C populations showed much higher variance in recovery time after CO exposure than after N exposure, suggesting gas-specific effects on pathways associated with locomotor recovery. Although these selection treatments result in considerable variation in life history attributes and body size, with the characteristic intermediacy of B populations, their superiority in resistance to gas exposure and locomotor recovery suggests that this is a direct consequence of prior repeated exposure to anoxia, broadly, and CO, specifically. Hence we describe a powerful new evolutionary model for the genetic and physiological investigation of anoxic coma in insects.