Location: Animal Parasitic Diseases
Title: Eimeria that infect fish are diverse and are related to, but distinct from, those that infect terrestrial vertebrates Authors
Submitted to: Infection, Genetics and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 14, 2012
Publication Date: December 1, 2012
Citation: Molnar, K., Ostoros, G., Dunams, D.B., Rosenthal, B.M. 2012. Eimeria that infect fish are diverse and are related to, but distinct from, those that infect terrestrial vertebrates. Infection, Genetics and Evolution. 12(8):1810-1815. Interpretive Summary: The Eimeria are a group of parasites known to cause extensive production losses to the poultry and livestock industries. These parasites are also abundant in wildlife hosts. Although a few species have been observed in fish, their relationship to the parasites of mammals and birds has never before been investigated. Here, we collected several parasites from fish, sequenced their ribosomal RNA genes, and compared these to those of other available sequences. Doing so allowed us verify that the Eimeria of fish and the Eimeria of other hosts are, indeed, related. In addition, we found evidence that the parasites of fish are very diverse, may be very old; we explore the possibility that parasites of fish were the ancestors of the parasites of other types of vertebrates, explaining the ultimate origins of this important parasite group. These results will be of interest to veterinarians, aquaculture practitioners, parasitologists, and evolutionary biologists.
Technical Abstract: The Eimeria are ubiquitous Apicoplexan parasites (family: coccidia) of the gut epithelium of vertebrates which complete their development in a single host species and whose sporocysts may be recognized by the presence of a Stieda body through which their sporozoites excyst. Their diversity and relationship to other kinds of coccidia have been successfully explored by molecular systematic studies based on the sequencing the 18S ribosomal DNA. To date, most attention has been paid to the diversity and evolutionary relationships of Eimeria spp. parasitizing terrestrial vertebrates, most especially those species infecting domesticated birds and mammals. Regrettably, no Eimeria have yet been considered from the Earth’s first vertebrates: the fish. If Eimeria first evolved in fish, then extant piscine parasites should comprise a deeply branching assemblage at the base of well-constructed phylogenetic trees. Here, we sequenced portions of ribosomal DNA from several such isolates (from Eimeria anguillae, E. daviesae, E. percae, E. variablis, E. rutili and E. nemethi) and compared them to one another as well as to other available sequences from the parasites of fish and terrestrial vertebrates, in order to better understand their diversity and origins. By establishing that such piscine parasites comprise a deeply branching clade at the base of the Eimeriidae, these data substantiate the hypothesis that Eimeria originated in fish. Plainly, a great deal of coccidian diversity awaits future discovery and description.