Biogeographic specializations of two large hypotrich ciliates: Australocirrus shii and A. australis and proposed synonymy of Australocirrus and Cyrtohymenides

Using standard methods, we studied the morphology and distribution of an Australian population of Australocirrus shii ( Shi et al., 1997) nov. comb. and a Jamaican population of A. australis ( Foissner, 1995) nov. comb. We identified three features, not or rarely used earlier, that distinguish Australocirrus shii from A. australis: the distance between the anterior pretransverse cirrus and the anteriormost transverse cirrus (5–8% vs. 1.5–1.7% of body length), the arrangement of the transverse cirri (3 + 2 vs. an oblique row), and the resting cyst macronuclear nodules (separate vs. fused). Australocirrus shii has been reported from Asia and Australia while A. australis is possibly restricted to the Neotropic. Because of problems in getting voucher materials of A. shii, we emphasise that permanent slides should be deposited in international repositories. Based on previous studies and new data, especially a refined interpretation of the shape of the paroral membrane, we suggest synonymy of Cyrtohymenides and Australocirrus. Thus, Cyrtohymena (Cyrtohymenides) shii, C. (Cyrtohymenides) aspoecki, and C. (Cyrtohymenides) australis are transferred to Australocirrus which is, inter alia, defined by a moderately to distinctly curved, but not recurved, paroral membrane, multiple fragmentation of dorsal kinety 3 and three or more dorsomarginal kineties.