title: Ultrastructure of Selenidium pendula, the Type Species of Archigregarines, and Phylogenetic Relations to Other Marine Apicomplexa.
abstract: Archigregarines, an early branching lineage within Apicomplexa, are a poorly-known group of invertebrate parasites. By their phylogenetic position, archigregarines are an important lineage to understand the functional transition that occurred between free-living flagellated predators to obligatory parasites in Apicomplexa. In this study, we provide new ultrastructural data and phylogenies based on SSU rDNA sequences using the type species of archigregarines, the Selenidiidae Selenidium pendulaGiard, 1884. We describe for the first time the syzygy and early gamogony at the ultrastructural level, revealing a characteristic nuclear multiplication with centrocones, cryptomitosis, filamentous network of chromatin, a cyst wall secretion and a 9+0 flagellar axoneme of the male gamete. S. pendula belongs to a monophyletic lineage that includes several other related species, all infecting Sedentaria Polychaeta (Spionidae, Sabellaridae, Sabellidae and Cirratulidae). All of these Selenidium species exhibit similar biological characters: a cell cortex with the plasma membrane - inner membrane complex - subpellicular microtubule sets, an apical complex with the conoid, numerous rhoptries and micronemes, a myzocytosis with large food vacuoles, a nuclear multiplication during syzygy and young gamonts. Two other distantly related Selenidium-like lineages infect Terebellidae and Sipunculida, underlying the ability of archigregarines to parasite a wide range of marine hosts.
authors.affiliation: Unité Molécules de Communication et Adaptation des Microorganismes, (MCAM, UMR 7245), Muséum National Histoire Naturelle, Sorbonne Universités, CNRS, CP 52, 57 Rue Cuvier, 75005 Paris, France. Electronic address: schrevel@mnhn.fr.
authors.forename: Joseph
authors.initials: J
authors.lastname: Schrével
authors.affiliation: Department of Botany and Zoology, Faculty of Science, Masaryk University, Kotlářská 2, 611 37 Brno, Czech Republic.
authors.forename: Andrea
authors.initials: A
authors.lastname: Valigurová
authors.affiliation: Cell Biology and Electron Microscopy Laboratory, François Rabelais University, 10 Boulevard Tonnellé, BP 3223, 37032 Tours Cedex, France.
authors.forename: Gérard
authors.initials: G
authors.lastname: Prensier
authors.affiliation: Laboratoire des Sciences de l'Environnement Marin (LEMAR), UMR6539 UBO/CNRS/IRD/IFREMER, Institut Universitaire Européen de la Mer (IUEM), Technopole Brest Iroise, 29280 Plouzané, France.
authors.forename: Aurélie
authors.initials: A
authors.lastname: Chambouvet
authors.affiliation: Unité Molécules de Communication et Adaptation des Microorganismes, (MCAM, UMR 7245), Muséum National Histoire Naturelle, Sorbonne Universités, CNRS, CP 52, 57 Rue Cuvier, 75005 Paris, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Florent
authors.affiliation: Sorbonne Universités, Université Pierre et Marie Curie - Paris 6, CNRS, UMR 7144, Station Biologique de Roscoff, Place Georges Teissier, CS90074, 29688 Roscoff cedex, France.
authors.forename: Laure
authors.initials: L
authors.lastname: Guillou
mesh_terms: D016782:Apicomplexa / Q000145:classification* / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure*; D016054:DNA, Protozoan / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D010802:Phylogeny
chemical_list: D016054:DNA, Protozoan; D004275:DNA, Ribosomal
keywords: Apicomplexa; Archigregarines; Selenidium pendula; phylogeny; sporozoite.; ultrastructure