Cytological Findings Suggesting Sexuality in Phytomonas davidi (Protozoa: Kinetoplastida)

Abstract

On few occasions, Phytomonas davidi (McGhee & Pastell isolate) cultures in LIT (liver infusiontryptose) medium around 27°C presented, as seen in Giemsa-stained smears, a set of peculiar morphological features, among them being noticeable the pairs of opposed cells attached by their posterior ends, where occurred a stained line and/or a dilatation, usually bulb-like in shape; sometimes this dilatation could occupy one of the cells or hold both together. In some pairs, the nucleus of each parasite seemed migrating towards the other, entering into such dilatation; in others, both nuclei were inside it, sometimes in close proximity or seeming fused; peculiar chromatin arrangements involving both nuclei were occasionally observed. Several mono or binucleate round forms bearing one or two flagella, as well as flagellate slender cells without nucleus were concomitantly seen there. In some instances, an intriguing small stained body occurred beside a single large nucleus, either in pairs presenting the bulb-like structure or in round cells. These cytological findings seemed steps of a dynamic process suggesting sexuality, since in several of them nuclear interactions following fusion of two parasites appeared to occur.