Cyrtolophosis elongata (Colpodea, Ciliophora): Some aspects of ciliary pattern, division, cortical and nuclear changes during encystment and resting cyst ultrastructure

Cyrtolophosis elongata is a small soil ciliate of the order Cyrtolophosidid a, class Colpodea. Using the silver carbonate method we have been able to s tudy the ciliary pattern of vegetative and dividing cells. Transmission ele ctron microscopy revealed that there is no micro-macronuclear complex in th is species. This type of nuclear apparatus thus cannot be considered as mos t important apomorphy of the Cyrtolophosidida. Division is in the swimming condition, stomatogenesis is pleurotelokinetal. Feulgen stain indicates the absence of a macronuclear chromatin extrusion process during both division and encystment. Cortical and cytoplasmic phenomena during encystment are s imilar to those of Colpoda spp. These data and ultrastructural observations of mature resting cysts indicate that Cyrtolophosis elongata has resting c ysts of PKR (Partial-kinetosome-resorbing) type, with a cyst wall composed by two layers.