Multiple origin of the dihomoxenous life cycle in sarcosporidia

Although their ssrRNA gene sequences are closely related, the lizard sarcos poridia (Apicomplexa, Sarcocystidae) Sarcocystis lacertae and Sarcocystis g allotiae posses heteroxenous and dihomoxenous life cycles, respectively. Wh en aligned with available sarcosporidian ssrRNA genes, both species contitu te a monophyletic clade that is only distantly related with sarcosporidia t hat have a viperid snake as their definitive host (Sarcocystis sp., Sarcocy stis atheridis). To test the phyletic status of the dihomoxenous life style , Sarcocystis rodentifelis and Sarcocystis muris, two dihomoxenous parasite s of mammals were included into this study. All studied species group toget her with former Frenkelia spp., Sarcocystis neurona and related marsupial a nd bird sarcosporidia in a monophyletic clade. However, the available datas et supports independent appearance of the dihomoxenous life cycle at least twice during the evolution of the Sarcocystidae. (C) 2001 Australian Societ y for Parasitology Inc. Published by Elsevier Science Ltd. All rights reser ved.