Intraerythrocytic 'gametocytes' of Babesia microti and their maturation in ticks

Abstract

The EM study of several strains of B. microti provided evidence that this parasite has 2 types of organisms in the intraerythrocytic stage. In one, the trophozoites undergo differentiation and reproduced by formation of merozoites. In the other no differentiation or reproduction occurs and the parasites acquire an unusual shape. The latter organisms might be gametocytes and this term is used tentatively throughout this paper. An examination of ticks fed hamster blood infected with B. microti showed that parasites emerging from hemolyzed erythrocytes closely resemble the intraerythrocytic gametocytes in their shape. A reorganization and differentiation of the cytoplasm expressed in the appearance of new structures occurs. Among them the most striking is a complex organelle that looks like an arrowhead. Several arrowheads are found in a single gametocyte, each marking an incipient gamete. Most gametes are equipped with an arrowhead organelle, a tail, microtubules and a cytostome. Occasionally a close apposition of 2 gametes and cytoplasmic fusion between the 2 organisms was found but this might represent division. The use of the terms gametocyte and gamete is not yet fully justified. More evidence is needed.