Phylogeny of fish-infecting Calyptospora species (Apicomplexa: Eimeriorina)

SUNY-ESF, State University of New York, College of Environmental Science and Forestry, Environmental and Forest Biology, 246 Illick Hall, 1 Forestry Drive, Syracuse, NY 13210, USA.
Parasitology Research (Impact Factor: 2.1). 05/2012; 111(3):1331-42. DOI: 10.1007/s00436-012-2969-8
Source: PubMed


There are numerous species of apicomplexans that infect poikilothermic vertebrates, such as fishes, and possess unique morphological features that provide insight into the evolution of this important phylum of parasites. Here, the relationship of the fish-infecting Calyptospora species to other coccidians was investigated based on DNA sequence analysis. Genetic data from the small subunit ribosomal DNA region of the genome were obtained for three of the five nominal species in the genus Calyptospora. Phylogenetic analyses supported a monophyletic lineage sister to a group composed of mostly Eimeria species. The monophyly of Calyptospora species supports the validity of the family Calyptosporidae, but the sister relationship to Eimeria species might also suggest the Eimeriidae be expanded to encompass Calyptospora. The validity of the family Calyptosporidae has been questioned because it is delineated from the Eimeriidae largely based on life cycle characteristics and sporocyst morphology. In general, Eimeria species have a homoxenous life cycle, whereas the type species of Calyptospora is heteroxenous. In the absence of experimental transmission studies, it may be difficult to demonstrate whether all Calyptospora species are heteroxenous. Other distinct morphological characteristics of Calyptospora such as an incomplete sporocyst suture, an apical opening for sporozoite release, a thin veil surrounding sporocysts supported by sporopodia, and a lack of Stieda and sub-Stieda bodies suggest there may be adequate features to delineate these taxa. Even without life cycle data for all species, the morphology and genetic data provide a means to reliably classify Calyptospora species. Placement in either the Calyptosporidae or Eimeriidae is discussed, along with issues relating to the phylogeny of the genus Goussia.

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    • "Indeed, two-valved sporocysts of Goussia spp. with a simple longitudinal suture seem to represent the ancestral state of the Sarcocystidae + Eimeriidae + Calyptosporidae clade, from which radiations into an array of excystation structures occurred (Jirků et al. 2002). These include the four-valved structures of sarcocystids, hemivalved arrangements with a thin membrane-covered oblong apical opening of the sporocyst wall of calyptosporids, and finally the univalved sporocysts containing Stieda and sub-Stieda bodies of eimeriids (Whipps et al. 2012). A similar scenario can be envisioned for the evolution of host-parasite interactions , with the ancestral epicellular location retained in G. janae and related species parasitizing coldblooded vertebrates, followed by a radiation of coccidians with various derived intracellular positions . "
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    • "Polymerase chain reactions were run in 50 μl volumes, consisting of 3 μl extracted DNA, 1X PCR buffer, 1.5 mM MgCl2, 0.2 mM dNTPs, 0.5 μM of each primer, 1.25 U Taq polymerase (Invitrogen), topped up with molecular grade water. Two sets of primers specific for coccidia were used for each sample; the 18E (5′-CTG GTT GAT CCT GCC AGT) forward and Coc2r (5′-CTT TCG CAG TAG TTC GTC) reverse primers were used to amplify the five prime region of ssrDNA, as previously described by Whipps et al. (2012) "
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    • "Notably, a considerably larger inter-species variation of the 18S rRNA gene is observed in Sarcocystidae (7.8–13.2%), as compared to some other apicomplexan pathogens as for example piroplasmids (0.3–8.2%) (Schnittger et al., 2003; Dahlgren and Gjerde, 2007; Gjerde, 2012; Whipps et al., 2012). The Bayesian tree shown in Fig. 2 demonstrates that the new 18S rRNA sequences originating from llama clustered in a single monophyletic group together with the corresponding sequence of S. aucheniae reported from an alpaca in Australia. "
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