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, Baccam and Lainson, 1990 developmental stages in the cane toad Bufo marinus L. and the vector tick Amblyomma rotondatum Koch, 1844 are described. In the liver of the toad, merozoites bound by a pellicle were located free and in the cytoplasm, and young and encased mature polynucleated meronts were located in a parasitophorous vacuole (PV). Premature gametocytes in the erythrocytes were bound by a bilayered membranous wall and the mature gametocytes were encased in a bivalved capsule, suture sites occurring at both gametocyte extremities. In the tick gut cells, oocysts located within a PV formed oblong, pellicle-bound sporokinetes, with a small apical complex, a few short rhoptries, and a fragmented crystalloid body. Liberated sporokinetes re-entered gut cells to proceed with their differentiation into sporocysts within a PV with elaborate rims which suggested engagement in active metabolite cross-transport. With maturity, the sporocyst wall gradually transformed into a hard capsule. Differences in fine structural development between species of Hemolivia and the insect-transmitted Hepatozoon are conspicuous. The 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 rhoptries rather than spherical-granular anlagen bodies, and fragmented rather than continuous crystalline bodies.