MORPHOGENESIS OF BIPARTITION IN 2 SPECIES OF THE GENUS PTYCHOSTOMUM (CILIOPHORA, HYSTEROCINETIDAE)

Two new species of Hysterocinetidae ciliates living parasitically in t he alimentary tract of Alma nilotica are described along with the proc ess of stomatogenesis in these species. The buccal primordium of the o pisthe originates from the multiplication of kinetosomes of some somat ic kinetics forming a disorganized field. One row of kinetosomes, a se cond and a third are successively isolated from this field. As soon as this stage with three rows of kinetosomes is reached, the peristomial infraciliature of the old buccal infraciliature progressively migrate s to the equator of the cell. There, it gives rise to the buccal infra ciliature of the proter through resorption and reorganization of the o ld buccal infraciliature. The description of this morphological develo pment is related to both nuclear division stages and the organization of the sucker cytoskeleton of the ciliates. Our findings contradict th e well admitted idea concerning the autonomous characteristic of the s tomatogenesis within the Hysterocinetidae. We propose that these cilia tes should be considered as a separate group within the Oligohymenopho ra.