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Cold-hardiness of the Antarctic winged midge Parochlus steinenii during the active season at King George Island

Research paper by K. Shimada, Y. Ohyama, C. X. Pan

Indexed on: 01 Sep '91Published on: 01 Sep '91Published in: Polar biology



Abstract

The Antarctic winged midge Parochlus steinenii (Diptera:Chironomidae) and its immatures were collected from freshwater lakes near Great Wall Station (62°13′S,58°58′W) on King George Island during January and February in 1990. They were examined for supercooling ability and lower lethal temperature. They were all intolerant to freezing. Supercooling points (spontaneous freezing points) of the larvae, pupae and adults were -7.4° ±1.0°, -16.3°±4.6° and -15.3°±5.6°C, respectively. These values represented the potential limits of cold-hardiness of this species. But the median lower lethal temperatures examined under an aqueous condition were always higher than the corresponding mean supercooling points. Half of the larvae, pupae and adults in the aqueous condition were killed at about -3°, -9° and -7°C, respectively, probably due to inoculative freezing. These temperatures seemed to be the natural lower limits of survival in the immatures and some adults of this species, at least in the active season.