CHOANOFLAGELLATES (ACANTHOECIDAE, CHOANOFLAGELLIDA) FROM THE WEDDELL SEA, ANTARCTICA, TAXONOMY AND COMMUNITY STRUCTURE WITH PARTICULAR EMPHASIS ON THE ICE BIOTA - WITH PRELIMINARY REMARKS ON CHOANOFLAGELLATES FROM ARCTIC SEA-ICE (NORTHEAST WATER POLYNYA, GREENLAND)

Ice biota studies in the Antarctic region, Weddell Sea, have focused o n an examination of single cells and an analysis of community structur e of the flagellate assemblage from sea ice and comparisons with plank tonic assemblages. Based on extensive light microscopical analysis of 40 samples ranging from open water to ''brown-ice'' habitats, it becam e evident through clustering of the data, that the mature choanoflagel late community from ice is significantly different from both the water column community and those encountered in samples derived from newly formed ice (i.e. grease ice, platelet ice, nilas and thin pancakes). T he choanoflagellates from sea ice encompasses a range of previously un described loricate taxa (Acanthocorbis nana sp. nov., A. weddellensis sp. nov., A. prolongata sp. nov., Apheloecion antarctica sp. nov., A. glacialis sp. nov., A. conicoides sp. nov., Calliacantha frigida sp. n ov., C. ankyra sp. nov., Diaphanoeca multiannulata subsp. nov. glacial is, Parvicorbicula corynocostata sp. nov., P. pachycostata sp. nov.). These taxa have been investigated using a combination of light, and el ectron microscopy. A preliminary investigation of samples from the Arc tic (NE Greenland) indicates that the loricate choanoflagellate divers ity is significantly lower in Arctic sea ice.