THE BIOLOGY, LIFE-CYCLE AND ECOPHYSIOLOGY OF THE ANTARCTIC MITE ALASKOZETES ANTARCTICUS

The cryptostigmatid mite Alaskozetes antarcticus (Michael) is a dominant member of many terrestrial communities in the maritime Antarctic, where it survives extreme temperatures, short cold summers, numerous freeze-thaw cycles, desiccating conditions and a limited season for growth and reproduction. However, examination of features of its biology, from morphology, through life-history strategy to physiology, indicate very little specialization to the Antarctic environment. Alaskozetes antarcticus is a herbivore/detritivore, typical of the Cryptostigmata in general, with low feeding and growth rates, long life span and low reproductive output. Physiological specializations exist in the form of low enzyme activation energies and elevated metabolic rates at low temperatures when compared with temperate species, and associated low optimum temperatures for activity, feeding and growth. Growth rates comparable with temperate species are achieved in the field, with an extended life cycle of five years or more as a result of the short growing season, and the ability of all life stages to overwinter equally successfully. Overwintering survival, involving supercooling enhanced by the use of antifreezes such as glycerol, although initially described in Antarctic species, is now known to be characteristic of many temperate relatives, so it is nor a specific adaptation to the polar environment. The obvious success of A. antarcticus in maritime Antarctic terrestrial environments must be attributed to a combination of several features characteristic of the Cryptostigmata in general, rather than to specific polar adaptations.