ECOLOGY OF THE LITTORAL HALACARIDAE (ACARI, PROSTIGMATA) OF SOUTH GEORGIA IN THE SUB-ANTARCTIC

Nine species of marine littoral Halacaridae were collected from Husvik Harbour, South Georgia, all of which are new to the fauna of the island. These include Isobactrus microdens Newell, Rhombognathus auster Bartsch, R. multisetosus Newell, R. plumifer Trouessart, Agauopsis inflatus Newell, Halacarellus novellus Bartsch and Pugh, H. porellus Bartsch and Pugh, Lohmannella bihamata Viets and L. grandipora Newell. The halacarid fauna is similar to that of southern South America, though depauperate and dominated by a single species, R. auster, which was found in large numbers and at all levels of the littoral zone. Low diversity probably results from isolation and/or severe climatic factors. Isolation includes both that of suitable habitable shores and the remoteness of South Georgia itself. The main climatic limitation is exposure to freezing air and icing during winter non-submergent neap tides.