EDAPHIC ORIBATID MITES (CRYPTOSTIGMATA, ACARINA) ASSOCIATED WITH AN AQUATIC MOSS ON SUB-ANTARCTIC SOUTH GEORGIA

The moss Drepanocladus uncinatus (Hedw.) Warnst., from coastal freshwa ter habitats on the sub-Antarctic island of South Georgia harbours two species of hemi-edaphic oribatid mite namely Edwardzetes elongatus Wa llwork (Ceratozetidae) and Trimaloconothrus flagelliformis Wallwork (M alaconothridae). Both mites feed upon microbiota and tolerate prolonge d submersion in freshwater and their survival among the aquatic moss i s a result of their pre-adaptation to similar conditions in flooded so il and vegetation, an absence of predators and minimal competition fro m other aquatic invertebrates. Freshwater habitats on sub-antarctic is lands are relatively young so that, in the future, terrestrial mites m ay eventually become displaced by more specialist aquatic macrofaunal colonists.