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 isla nd. These include Isobactrus microdens Newell, Rhombognathus auster Ba rtsch, R. multisetosus Newell, R. plumifer Trouessart, Agauopsis infla tus Newell, Halacarellus novellus Bartsch and Pugh, H. porellus Bartsc h and Pugh, Lohmannella bihamata Viets and L. grandipora Newell. The h alacarid fauna is similar to that of southern South America, though de pauperate and dominated by a single species, R. auster, which was foun d in large numbers and at all levels of the littoral zone. Low diversi ty probably results from isolation and/or severe climatic factors. Iso lation includes both that of suitable habitable shores and the remoten ess of South Georgia itself. The main climatic limitation is exposure to freezing air and icing during winter non-submergent neap tides.