Infraciliature and morphogenesis of Paraholosticha sterkii (Garnjobst, 1934) n. comb. (Ciliophora, Hypotrichida).

The infraciliature and morphogenesis of Paraholosticha sterkii (Garnjobst, 1934) n. comb. (Basionym: Stylonethes sterkii) are described. Before division a cell encysts and after division each tomite forms an individual cyst within the common one. The ciliates cease to move and the kinetome is resorbed. With the beginning of morphogenesis new kinetosomes appear and an oral primordium is formed, where the differentiation of adoral membranelles is visible at an early state. At the same time the anlagen of the marginal rows of cirri, of the undulating membranes and the fronto-ventral complex of cirri develop. After differentiation of the kinetome the tomites hatch. If food is removed P. sterkii forms resting cysts. Encystation and excystation can be induced experimentally. The morphogenesis during excystation is apparently identical to the morphogenesis after division. It is synchronous in 80 to 90% of the cells. Paraholosticha Kahl, 1932 is separated from Keronopsis Penard, 1922 by the possession of transverse cirri. Thus, the species investigated is a typical representative of the genus Paraholosticha.