Notes on the ecology and physiology of the Antarctic oribatid mite Maudheimia wilsoni

Abstract

The oribatid mite Maudheimia wilsoni Dalenius was found to be numerous on the underside of stones at Jutulsessen (72°S, 3?E) in Dronning Maud Land, Antarctica. Daily temperature fluctuations of the microhabitat from as high as 19°C and to as low as – 17°C were observed during the austral summer. Optimal activity of the mites occurred at 10°C. Even in January the mean supercooling point of adult mites was as low as -30.8±4.7°C. Haemolymph osmolality ranged from 500 to 800mOsmol and thermal hystersis freezing points from ?4.7 to ?6.1°C. Adult mites had a mean water content of 43.6% and a water loss rate of 0.12 ?gh?1 at 15°C and 10% relative humidity.