title: Molecular phylogeny and ultrastructure of Aphelidium aff. melosirae (Aphelida, Opisthosporidia).
abstract: Aphelids are a poorly known group of parasitoids of algae that have raised considerable interest due to their pivotal phylogenetic position. Together with Cryptomycota and the highly derived Microsporidia, they have been recently re-classified as Opisthosporidia, being the sister group to fungi. Despite their huge diversity, as revealed by molecular environmental studies, and their phylogenetic interest, only three genera have been described (Aphelidium, Amoeboaphelidium, and Pseudaphelidium), from which 18S rRNA gene sequences exist only for Amoeboaphelidium species. Here, we describe the life cycle and ultrastructure of Aphelidium aff. melosirae, and provide the first 18S rRNA gene sequence obtained for this genus. Molecular phylogeny analysis indicates that Aphelidium is very distantly related to Amoebaphelidium, highlighting the wide genetic diversity of the aphelids. The parasitoid encysts and penetrates the host alga, Tribonema gayanum through an infection tube. Cyst germination leads to a young trophont that phagocytes the algal cell content and progressively develops a plasmodium, which becomes a zoospore-producing sporangium. Aphelidium aff. melosirae has amoeboflagellate zoospores, tubular/lamellar mitochondrial cristae, a metazoan type of centrosome, and closed orthomitosis with an intranuclear spindle. These features together with trophont phagocytosis distinguish Aphelidium from fungi and support the erection of the new superphylum Opisthosporidia as sister to fungi.
authors.affiliation: Zoological Institute, Russian Academy of Sciences, St. Petersburg 199034, Russian Federation; St. Petersburg State University, St. Petersburg 199034, Russian Federation; Institut de Minéralogie et de Physique des Milieux Condensés, Université Pierre et Marie Curie et CNRS, 4 place Jussieu. 75252 Paris cedex 05, France. Electronic address: sakarpov4@gmail.com.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Karpov
authors.affiliation: St. Petersburg State University, St. Petersburg 199034, Russian Federation.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Mamkaeva
authors.affiliation: Institut de Minéralogie et de Physique des Milieux Condensés, Université Pierre et Marie Curie et CNRS, 4 place Jussieu. 75252 Paris cedex 05, France.
authors.forename: Karim
authors.initials: K
authors.lastname: Benzerara
authors.affiliation: Unité d'Ecologie, Systématique et Evolution, UMR CNRS 8079, Université Paris-Sud. 91405 Orsay cedex, France.
authors.forename: David
authors.initials: D
authors.lastname: Moreira
authors.affiliation: Unité d'Ecologie, Systématique et Evolution, UMR CNRS 8079, Université Paris-Sud. 91405 Orsay cedex, France. Electronic address: puri.lopez@u-psud.fr.
authors.forename: Purificación
authors.initials: P
authors.lastname: López-García
mesh_terms: D056890:Eukaryota / Q000145:classification* / Q000235:genetics / Q000648:ultrastructure*; D014644:Genetic Variation / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D012337:RNA, Ribosomal, 18S / Q000235:genetics
chemical_list: D012337:RNA, Ribosomal, 18S
keywords: Rozella; ecology.; life cycle; molecular phylogeny; parasitoids; ultrastucture