The Infraciliature of two Sapropelic Heterotrich Ciliates, Cirranter mobilis and Saprodinium dentatum (Ciliophora, Heterotrichida)

Summary The infraciliature of two sapropelic heterotrich ciliates, Cirronter mobilis and Saprodinium dentatum , is described. The somatic infraciliature of C. mobilis is constituted by a pcrizonal zone and one kinety of the bell. The perizonal zone is formed by numerous short longitudinal kinelies with 4 kinetids each (dikinetids). Complex longitudinal fibrillar systems connect the kinetosomes of each kinety. The kinety of the bell is composed of two rows of kinetosomes with long fibrillar derivates. In the oral zone, the paroral membrane is formed by one row of kinetosomes, and the adoral zone of membranelles is constituted by numerous membranelles each one with two rows of kinetosomes. Ihese membranelles are connected one another through transversal microfibrillar tracts. Our observations concerning the somatic infraciliature of S. dentatum indicate that the perizonal zone (PZ), the longitudinal somatic kineties (LK) and the kineties of the spines (SK) are closely related between them. The right extremes of each kinetosomal row of the PZ continuate with somatic longitudinal kinetics, which lack of fibrillar derivates. Moreover, the SK constitute the modified posterior extremes of some of LK. At the ventral margin of ciliate, the most posterior row of kinetosomes of the PZ is connected through fibrillar bundles with two short rows of kinetosomes (additional kineties) with a complex cytoskeletal array. Groups of 2–4 kinetosomes without fibrillar associates constitute the infraciliature of the bell kinety. The oral infraciliature ol this species is composed by 9–10 membranelles each one with 2–3 kinetosomal rows of different length and 2–3 argentophilic rows, which as in C. mobilis , have not been described until now.