Ultrastructural comparison of Hepatozoon ixoxo and Hepatozoon theileri (Adeleorina: Hepatozoidae), parasitising South African Anurans

Abstract

To date, only two haemogregarine parasite species have been described from South African anurans: Hepatozoon ixoxo, infecting toads of the genus Scler- ophrys (syn. Amietophrynus); and Hepatozoon theileri, parasitising the com- mon river frog, Amietia quecketti. Both species have been characterised using limited morphology, and molecular data from PCR amplified fragments of the 18S rRNA gene. However, no ultrastructural work has been performed thus far. The aim of this study was to add descriptive information on the two spe- cies by studying their ultrastructural morphology. Mature gamont stages, com- mon in the peripheral blood of infected frogs, were examined by transmission electron microscopy. Results indicate that H. ixoxo and H. theileri share typical apicomplexan characteristics, but differ markedly in their external cellular struc- ture. Hepatozoon ixoxo is an encapsulated parasite presenting a prominent cap at the truncate pole, and shows no visible modifications to the host cell mem- brane. In comparison, H. theileri does not present a capsule or cap, and pro- duces marked morphological changes to its host cell. Scanning electron microscopy was performed to further examine the cytopathological effects of H. theileri, and results revealed small, knob-like protrusions on the erythrocyte surface, as well as notable distortion of the overall shape of the host cell