Phylogenetic relationships of Hepatozoon (Apicomplexa : Adeleorina) based on molecular, morphologic, and life-cycle characters

To evaluate higher-level affinities of Hepatozoon species within Apicomplex a, we sequenced the 18S rRNA gene fi-om 2 parasites (Hepatozoon americanum and Hepatozoon canis) of dogs and 1 (Hepatozoon catesbianae) of bullfrogs. Sequences from other apicomplexans among the Sarcocystiidae, Eimeriidae, Th eileriidae, Plasmodiidae, Cryptosporiidae, and Babesiidae, a Perkinsus spec ies and 2 dinoflagellates were obtained from GenBank. Phylogenetic analysis indicated that Plasmodium, Cryptosporidium. and Hepatozoon form a monophyl etic group distinct from representatives of other apicomplexan families. Al though equivocal, our analysis indicated that Plasmodium and Cryptosporidiu m are sister taxa and that Hepatozoon is basal to them. To evaluate phyloge netic affinities among H. americanum, H. canis, and other species of Hepato zoon, we examined Is morphologic and life-cycle features of 13 species curr ently assigned to Hepatozoon. This analysis indicates paraphyly of Hepatozo on cas currently arranged) because Hepatozoon lygosomarum was found most cl osely related to Hemollvia mauritanicum. These results, combined with resul ts of previous studies, support elevating Hepatozoon to familial level (Hep atozoidae) as originally suggested by Wenyon in 1926. Both DNA sequence dat a and morphologic and life-cycle characters support a sister-group relation ship between H. americanum and H. canis.