Comparative fine structure study of the gametocytes of avian, reptilian, and mammalian malarial parasites

Abstract

The fine structures of the gametocytes of various malarial parasites were investigated and compared. The malarial parasites studied include Plasmodium lophurae, P. cathemerium, P. gallinaceum, P. pinotti, P. elongatum (all avian parasites), P. floridense (reptilian parasite), and P. knowlesi and P. cynomolgi (mammalian parasites). The gametocytes of these malarial parasites can be distinguished from the parasites of the asexual stages on the basis of the fine structures. A three-layered pellicle is very pronounced in the gametocytes of avian and reptilian malarial parasites, but less so in those of mammalian parasites. Gametocytes of avian and reptilian parasites differ from mammalian ones by their distinct mitochondria and round osmiophilic bodies, whereas the mammalian parasites show double membrane-bounded structures, possibly a mitochondrial equivalent, and elongated osmiophilic bodies. The macrogametocyte differs from the microgametocyte in that the former possesses more ribosomes, more developed endoplasmic reticulum, and more osmiophilic bodies than the latter. In addition to these differences, the mature microgametocyte shows electron dense aggregates in the nucleus and kinetosomes in the cytoplasm. A possible origin of the gametocytes from asexual merozoites is also discussed.