CYTOLOGICAL FINDINGS SUGGESTING SEXUALITY IN PHYTOMONAS-DAVIDI (PROTOZOA, KINETOPLASTIDA)

On few occasions, Phytomonas davidi (McGhee & Postell isolate) culture s in LIT (liver infusion-tryptose) medium around 27 degrees C presente d, as seen in Giemsa-stained smears, a set of peculiar morphological f eatures, among them being noticeable the pairs of apposed cells attach ed by their posterior ends, where occurred a stained line and/or a dil atation, usually bulb-like in shape; sometimes this dilation could occ upy one of the cells or hold both together. In some pairs, the nucleus of each parasite seemed migrating towards the other, entering into su ch dilatation; in others, both nuclei were inside it, sometimes in clo se proximity or seeming fused; peculiar chromatin arrangements involvi ng both nuclei were occasionally observed. Several mono or binucleate round forms hearing one or two flagella, as well as flagellate slender cells without nucleus were concomitantly seen there. In some instance s, an intriguing small stained body occurred beside a single large nuc leus, either in pairs presenting the bulb-like structure or in round c ells. These cytological findings seemed steps of a dynamic process sug gesting sexuality since in several of them nuclear interactions follow ing fusion of two parasites appeared to occur.