Cell division and morphology of the marine ciliate, Condylostoma spatiosum Ozaki and Yagiu (Ciliophora, Heterotrichida) based on a Chinese population

The morphology and morphogenesis of the large marine heterotrichous ciliate, Condylostoma spatiosum Ozaki & Yagiu in Yagiu, 1944, isolated from Jiaozhou Bay off Qingdao (Tsingtao), China, were investigated using live observation and protargol impregnation. A detailed redescription is given since no infraciliature data about this “well-studied” species are available. It is characterized by: size in vivo 400–700×90–140 μm; buccal field about 1/3 of body length; adoral zone composed of 130 membranelles on average; invariably two prominent membrane-like frontal cirri, which are parallel to each other; about 58 somatic kineties; macronucleus composed of 13–22 fragments. Morphogenesis proceeds basically as described in a previous report and can be summarized as follows: (1) the parental adoral zone of membranelles is partly dedifferentiated and then renewed in the posterior portion; (2) in the proter, both the frontal cirri and the paroral membrane are newly formed by anlagen derived from the disaggregated old structures; (3) in the opisthe the anlagen of the paroral membrane and the frontal cirri develop from the right margin of the oral primordium; (4) two frontal cirri are formed one after the other by the frontal cirral anlage; (5) during morphogenesis, no recognizable duplication of basal bodies takes place in somatic kineties; and (6) the macronucleus divides after prior fusion. One reorganizer was observed showing that the basic process of reorganization is obviously similar to that in division.