Life cycle, host restriction and longevity of Babesiosoma mariae HOARE, 1930 (Apicomplexa: Dactylosomatidae)

Morphometric and morphological observations on B. mariae in an experimentally infected fish (using the leech vector Batracobdeloides tricarinata for the first time) revealed that three successive types of merogonic cycles occurred within the fish erythrocytes. The third cycle produced merozoites destined to become gamonts. The gamonts were somewhat larger than merogonic stages and comprised the majority of the parasitic stages during parasitaemia for up to 7 months. In the leech crop gamonts released from the fish blood became associated in syzygy and fused. The formed zygote underwent sporogony within the gut tissues and up to 8 sporozoites budded simultaneously from the periphery of an irregularly shaped oocyst. The sporozoites underwent merogony typical as that of erythrocytic merogony mainly in the salivary tissues. The merozoites either initiated a further cycle of merogony or moved towards the proboscis. The babesiosomes survived in the leech over a period of 9 months involving 7 meals after the initial meal provided the fasting period did not exceed 60-90 days. Survival was attributed to residual stages in the salivary glands. Cross transmission experiments between fishes via B. tricarinata revealed that the fish babesiosomes were not host specific. Previously described African fresh water fish dactylosomatids were indistinguishable from each other and on the basis of the current results, they are regarded as a single species Babesiosoma mariae.