Edaphic oribatid mites (Cryptostigmata: Acarina) associated with an aquatic moss on sub-Antarctic South Georgia

The moss Drepanocladus uncinatus (Hedw.) Warnst., from coastal freshwater habitats on the sub-Antarctic island of South Georgia harbours two species of hemi-edaphic oribatid mite namely Edwardzetes elongatus Wallwork (Ceratozetidae) and Trimaloconothrus flagelliformis Wallwork (Malaconothridae). Both mites feed upon microbiota and tolerate prolonged submersion in freshwater and their survival among the aquatic moss is a result of their pre-adaptation to similar conditions in flooded soil and vegetation, an absence of predators and minimal competition from other aquatic invertebrates. Freshwater habitats on sub-Antarctic islands are relatively young so that, in the future, terrestrial mites may eventually become displaced by more specialist aquatic macrofaunal colonists.