The oral apparatus of Colpoda variabilis (Ciliophora, Colpodidae): II. Ultrastructure of the oral ciliature and its implications on ciliate phylogeny.

The oral ciliature of Colpoda variabilis has been examined by serial thin sections. The left oral polykinetid consists of parallel rows of ciliated kinetosomes. The right oral polykinetid consists of a ventral part of ciliated kinetosomes in anarchic arrangement and a dorsal double row of ciliated kinetosomes. The existence of postciliary microtubules in association with each kinetosome makes it possible to determine the orientation of kinetosomes within the oral polykinetids. The orientation of kinetosomes in oral polykinetids and oral primordia is discussed and compared with the oral ciliature of Furgasonia, Paramecium and Tetrahymena. The left oral polykinetid is interpreted as consisting of adorai membranelies and the right oral polykinetid is interpreted as consisting of a stichodyad type of paroral membrane accompanied by a ciliary field in anarchic arrangement. A closer phylogenetic relationship between colpodid, nassulid and hymenostome ciliates is suggested.