Fine structure and Molecular Phylogenetic Position of Two Marine Gregarines, Selenidium pygospionis sp. n. and S. pherusae sp. n., with Notes on the Phylogeny of Archigregarinida (Apicomplexa)

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Authors	PASKEROVA Gita G. MIROLIUBOVA Tatiana S. DIAKIN Andrei KOVÁČIKOVÁ Magdaléna BARDŮNEK VALIGUROVÁ Andrea GUILLOU Laure ALEOSHIN Vladimir V. SIMDYANOV Timur G.
Year of publication	2018
Type	Article in Periodical
Magazine / Source	Protist
MU Faculty or unit	Faculty of Science
Citation
Web	https://www.sciencedirect.com/science/article/pii/S143446101830066X
Doi	http://dx.doi.org/10.1016/j.protis.2018.06.004
Keywords	Unicellular parasites polychaetes ultrastructure18S rDNA28S rDNA molecular phylogeny.
Description	Archigregarines are a key group for understanding the early evolution of Apicomplexa. Here we report morphological, ultrastructural, and molecular phylogenetic evidence from two archigregarine species: Selenidium pygospionis sp. n. and S. pherusae sp. n. They exhibited typical features of archigregarines. Additionally, an axial row of vacuoles of a presumably nutrient distribution system was revealed in S. pygospionis. Intracellular stages of S. pygospionis found in the host intestinal epithelium may point to the initial intracellular localization in the course of parasite development. Available archigregarine SSU (18S) rDNA sequences formed four major lineages fitting the taxonomical affiliations of their hosts, but not the morphological or biological features used for the taxonomical revision by Levine (1971). Consequently, the genus Selenidioides Levine, 1971 should be abolished. The branching order of these lineages was unresolved; topology tests rejected neither para- nor monophyly of archigregarines. We provided phylogenies based on LSU (28S) rDNA and near-complete ribosomal operon (concatenated SSU, 5.8S, LSU rDNAs) sequences including S. pygospionis sequences. Although being preliminary, they nevertheless revealed the monophyly of gregarines previously challenged by many molecular phylogenetic studies. Despite their molecular-phylogenetic heterogeneity, archigregarines exhibit an extremely conservative plesiomorphic structure; their ultrastructural key features appear to be symplesiomorphies rather than synapomorphies.
Related projects:	ECIP - Evropské centrum ichtyoparazitologie