Morphology and cell division of Saudithrix terricola n. gen., n. sp., a large, stichotrich ciliate from Saudi Arabia.

The morphology and main ontogenetic traits of a new stichotrich ciliate, Saudithrix terricola Foissner, AL-Rasheid and Berger n. gen., n. sp., from a terrestrial habitat in Saudi Arabia were investigated using live observation, protargol impregnation, and scanning electron microscopy. Saudithrix terricola is characterized by a large (200–350 _ 70–150 mm), flexible body; an adoral zone formed like a three-quarter circle; a sickle-shaped buccal lip with a widened paroral forming a cyrtohymenid pattern with the endoral; 11 frontal and frontal-ventral cirral rows (including right marginal rows) and one left marginal row covering the ventral side; two buccal cirri; ix to nine transverse cirri; three dorsal kineties; and two macronuclear nodules. The resting cyst is about 85 mm across, has a smooth wall, and a fluffy mucous layer. Most cirral anlagen originate within the parental rows and are arranged side by side, the proximal portion of the adoral zone of membranelles is reorganized, and some parental dorsal bristles are maintained. Neither the morphological nor the ontogenetic data reveal the systematic position of Saudithrix within the stichotrichs. The term multicorona is introduced and describes a frontal ciliature composed of four or more cirral bows