Leishmania major: parasite interactions suggesting sexuality

RESUMO

In five experiments, Leishmania (Leishmania) major (MRHO/SU/59/P-strain) grew poorly when seeded in FYTS medium supplemented with 15 per cent fetal calf serum, but presented several peculiar pairs of promastigotes diametrically opposed and attached at their posterior ends (5.8-13.5 per cent). As seen in Giemsa-stained smears, a ring-like line and/or an enlargement, generally occured at the parasite junction. A close proximity of nuclei, which sometimes were difficult to distinguish from each other, was also observed at this junction. Several of these pairs appeared to be composed of fused cells in which the nuclei could be apparently fused, as shown by fluorescence microscopy to detect ß-tubulin and DNA, and by scanning electron microscopy. Under other culture conditions these pairs were absent or occurred at very low rates (0.2-2.2 per cent). Such pairs differ markedly from longitudinally dividing cells and resemble those described in two other Leishmania species, as well as in Herpetomonas megaseliae and Phytomonas davidi, suggesting steps of a putative sexual process.