A Contribution to the Systematics of the Reptilian Malaria Parasites, Family Plasmodiidae (Apicomplexa: Haemospororina)

Abstract

The malaria parasites of reptiles, represented by over 80 known species, belong to three genera of the Plasmodiidae: Plasmodium, Fallisia, and Saurocytozoon. Plasmodium, containing most of the species, is comprised of seven subgenera: Sauramoeba, Caninamoeba, Lacertamoeba, Paraplasmodium, Asiamoeba, Garnia, and Ophidiella. Of these, Lacertamoeba, Paraplasmodium, and Asiamoeba are new subgenera. The subgenera are defined on the basis of morphometric relationships of the pigmented species, by the absence of pigment (Garnia), or by their presence in ophidian hosts (Ophidiella). The pigmented species with schizonts and gametocytes of similar size are divided into three groups with little or no morphometric overlap: Sauramoeba, with very large gametocytes and schizonts, which undergo 4 to 7 nuclear divisions in the erythrocytic phase of the life cycle; Carinamoeba, with very small gametocytes and schizonts, that have 2 or 3 divisions; and Lacertamoeba, with medium-sized gametocytes and schizonts, which undergo 3 to 5 nuclear divisions. Lacertamoeba species that overlap morphometrically with Carinamoeba can be distinguished from the latter by their larger range of merozoite numbers. Two species groups have schizonts and gametocytes of dissimilar size: Paraplasmodium has large gametocytes but schizonts of only medium size, while Asiamoeba has gametocytes 4 to 15 times the schizont size. Paraplasmodium is further distinguished by containing the only species known to undergo normal sporogony in a psychodid fly (Lutzomyia), and by its capacity to produce exoerythrocytic schizonts in both fixed and wandering host cells. Fallisia is characterized by having both asexual and sexual cycles in non-erythrocytic blood cells, while the asexual stages of Saurocytozoon appear to be transitory in circulating lymphocytes, disappearing when gametocytes, largely confined to lymphocytes, become evident.