Description of Arcuospathidium australe
provided by BioPedia
Predatory ciliate, 120-180 X 35-55 microns, highly contractile, four macronuclear segments on average, three raised ridges on left side, two diagonally opposed contractile vacuoles, 10-12 right lateral and three to four left lateral somatic kineties. Shape broad in middle, tapering anterior and posterior, ends slightly rounded. Depending on nutritional state, slightly to heavily flattened (up to l:4). Right side flat to slightly concave. Left side slightly to greatly convex in middle and with three raised ridges (separated by two depressions) bearing somatic kineties. Body highly flexible, about one third of body length contractile. Macronuclear segments centrally-located, variable in number (most cells containing four), usually arranged in a single row along midline. Micronuclei spherical, located close to macronuclear segments, typically two present but occasionally with one or three. One contractile vacuole located right anterior at beginning of middle third of body, a second contractile vacuole located left posterior subterminal. Extrusomes about 7 microns long, gently curved, located along the entire margin of body. No trichocyst warts. Pellicle and endoplasm colourless. Body very hyaline, particularly at ends and along sides. Food vacuoles concentrated in middle portion of cell. In culture, observed to feed on ciliates (Cinetochilum margaritaceum, Cyclidium sp.). Movement by slow gliding and/or rotating around long axis. Cilia of right side about 7 microns long. Right somatic kineties densely ciliated, becoming successively shortened anteriorly along mouth. Kineties also shortened left and especially right posteriorly as evidenced by course of fibrillar system. Two unshortened dorsolateral kineties curving posteriorly around the kineties of right side and ending next to first and third perioral kineties. Four somatic kineties on left side strongly shortened posteriorly, bearing 2 microns long bristle-like cilia. Leftmost kinety densely ciliated, anterior portion with paired basal bodies forming brosse, anterior end of this kinety moderately to heavily fragmented. Three perioral kineties about three quarters length of body, two on right, one on left of mouth. Second perioral kinety shortened slightly posteriorly. First and second perioral kineties with paired basal bodies, cilia arising only from anterior basal body. Cilia of first kinety short and bristle-like about 2 microns long, those of second kinety normal in length. Third perioral kinety with single basal bodies, arranged closely together, with normal cilia. Nematodesma very fine.
