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Protist. 2018 Dec;169(6):826-852. doi: 10.1016/j.protis.2018.06.004. Epub 2018 Jun 28.

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).

Author information

1
Department of Invertebrate Zoology, Faculty of Biology, Saint Petersburg State University, Universitetskaya emb. 7/9, St Petersburg 199 034, Russian Federation. Electronic address: gitapasker@yahoo.com.
2
Department of Invertebrate Zoology, Faculty of Biology, Saint Petersburg State University, Universitetskaya emb. 7/9, St Petersburg 199 034, Russian Federation.
3
Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic.
4
Sorbonne Université, Université Pierre et Marie Curie - Paris 6, CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, CS90074, 29688 Roscoff Cedex, France.
5
Belozersky Institute for Physico-Chemical Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow 119 234, Russian Federation.
6
Department of Invertebrate Zoology, Faculty of Biology, Lomonosov Moscow State University, Leninskie Gory, Moscow 119 234, Russian Federation.

Abstract

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.

KEYWORDS:

18S rDNA; 28S rDNA; Unicellular parasites; molecular phylogeny.; polychaetes; ultrastructure

PMID:
30453272
DOI:
10.1016/j.protis.2018.06.004
[Indexed for MEDLINE]

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