Population Differences in Antifreeze/Cryoprotectant Accumulation Patterns in an Antarctic Insect

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Abstract
The freezing tolerant antarctic midge Belgica antarctica Jacobs accumulates a 3 component cryoprotectant system during the period of seasonal transition (Feb.-March). Separate populations produce qualitatively identical cryoprotectants (erythritol, glucose and trehalose), but with quantitative variations that may yield a doubling in levels of 1 or more individual cryoprotectants. These quantitative variations occur under identical thermal and photic conditions. The protective potential of cryoprotectants when represented as a combined indicator of concentration (hydroxyl equivalents) is essentially equal among populations as hardening is maximized. Supercooling points elevate from austral summer lows of -10.2.degree. to winter highs of -5.0.degree. C. The accumulation of cryoprotectants occurs concomitantly with the gradual decrease in microhabitat temperatures (0.20.degree.-0.25.degree. C/day). Enhanced hardening is probably not alone triggered by temperature, but may be associated with other environmental stressors or development programming.