A light and electron microscopical investigation of loricate choanoflagellates (Choanoflagellida, Acanthoecidae) from the Andaman Sea, SW Thailand and Denmark: Species of Cosmoeca gen.n.

The choanoflagellate genus Cosmoeca gen.n. is characterized by a very regular arrangement of rod-shaped costal strips, forming 9–12 longitudinal costae (each composed of 3–4 costal strips) and 2–3 transverse costae. Anteriorly the longitudinal costae attach the transverse costae at the joints between neighbouring transverse costal strips. Five species of Cosmoeca are described: C. norvegica sp.n. (type species; previously referred to as sp. “N”), C. ventricosa sp.n., C. phuketensis sp., C. subulata sp.n. and C. ceratophora sp.n. Cosmoeca ventricosa sp.n. is obviously part of a form complex, the extent of which has not yet been fully explained. In this paper, three groups of specimens clearly related to C. ventricosa sp.n. are illustrated and briefly described (C. ventricosa forms A. B, C). Form A appears to be identical to Pleurasiga orculaeformis Schiller, 1925, sensu Leadbeater.