Ultrastructure of developmental stages of Hemolivia stellata (Apicomplexa : Haemogregarinidae) in the cane toad Bufo marinus and in its vector tick Amblyomma rotondatum

The fine structure of the hemogregarine Hemolivia stellata Petit, Landau, B accam and Lainson, 1990 developmental stages in the cane toad Bufo marinus L. and the vector tick Amblyomma rotondatum Koch, 1844 are described. In th e liver of the toad, merozoites bound by a pellicle were located free and i n the cytoplasm, and young and encased mature polynucleated meronts were lo cated in a parasitophorous vacuole (PV). Premature gametocytes in the eryth rocytes were bound by a bilayered membranous wall and the mature gametocyte s were encased in a bivalved capsule, suture sites occurring at both gameto cyte extremities. In the tick gut cells, oocysts located within a PV formed oblong, pellicle-bound sporokinetes, with a small apical complex, a few sh ort rhoptries, and a fragmented crystalloid body. Liberated sporokinetes re -entered gut cells to proceed with their differentiation into sporocysts wi thin a PV with elaborate rims which suggested engagement in active metaboli te cross-transport. With maturity, the sporocyst wall gradually transformed into a hard capsule. Differences in fine structural development between sp ecies of Hemolivia and the insect-transmitted Hepatozoon are conspicuous. T he fine structure and course of development of H. stellata are very similar to those of the previously described Hemolivia mariae; their sporokinetes, differ, however, in having conspicuous rhoptrias rather than spherical-gra nular anlagen bodies, and fragmented rather than continuous crystalline bod ies.