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Protist. 2018 Nov;169(5):697-726. doi: 10.1016/j.protis.2018.04.006. Epub 2018 Apr 23.

First Ultrastructural and Molecular Phylogenetic Evidence from the Blastogregarines, an Early Branching Lineage of Plesiomorphic Apicomplexa.

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Faculty of Biology, Lomonosov Moscow State University, Leninskiye Gory 1-12, 119 234 Moscow, Russian Federation. Electronic address:
Department of Invertebrate Zoology, Faculty of Biology, Saint Petersburg State University, Universitetskaya emb. 7/9, 199 034 St. Petersburg, Russian Federation.
Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic.
CNRS 7245, Molécules de Communication et Adaptation Moléculaire (MCAM), CP 52, rue Cuvier, 75005 Paris, France; Sorbonne Universités, Muséum National d'Histoire Naturelle (MNHN), UMR 7245, CP 52, rue Cuvier, 75005 Paris, France.
Sorbonne Université, Université Pierre et Marie Curie-Paris 6, CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, CS90074, 29688 Roscoff Cedex, France.
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Leninskiye Gory 1-40, 119 234 Moscow, Russian Federation; Institute for Information Transmission Problems, Russian Academy of Sciences, Bolshoy Karetny per. 19-1, 127 051 Moscow, Russian Federation.


Blastogregarines are poorly studied parasites of polychaetes superficially resembling gregarines, but lacking syzygy and gametocyst stages in the life cycle. Furthermore, their permanent multinuclearity and gametogenesis by means of budding considerably distinguish them from other parasitic Apicomplexa such as coccidians and hematozoans. The affiliation of blastogregarines has been uncertain: different authors considered them highly modified gregarines, an intermediate apicomplexan lineage between gregarines and coccidians, or an isolated group of eukaryotes altogether. Here, we report the ultrastructure of two blastogregarine species, Siedleckia nematoides and Chattonaria mesnili, and provide the first molecular data on their phylogeny based on SSU, 5.8S, and LSU rDNA sequences. Morphological analysis reveals that blastogregarines possess both gregarine and coccidian features. Several traits shared with archigregarines likely represent the ancestral states of the corresponding cell structures for parasitic apicomplexans: a distinctive tegument structure and myzocytotic feeding with a well-developed apical complex. Unlike gregarines but similar to coccidians however, the nuclei of male blastogregarine gametes are associated with two kinetosomes. Molecular phylogenetic analyses reveal that blastogregarines are an independent, early diverging lineage of apicomplexans. Overall, the morphological and molecular evidence congruently suggests that blastogregarines represent a separate class of Apicomplexa.


18S and 28S ribosomal DNAs.; Apicomplexa; blastogregarines; molecular phylogeny; plesiomorphic traits; ultrastructure

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