title: Molecular Phylogeny and Evolutionary Relationships between the Ciliate Genera Peniculistoma and Mytilophilus (Peniculistomatidae, Pleuronematida).
abstract: Peniculistoma mytili and Mytilophilus pacificae are placed in the pleuronematid scuticociliate family Peniculistomatidae based on morphology and ecological preference for the mantle cavity of mytiloid bivalves. We tested this placement with sequences of the small subunit rRNA (SSUrRNA) and cytochrome c oxidase subunit 1 (cox1) genes. These species are very closely related sister taxa with no distinct genetic difference in the SSUrRNA sequence but about 21% genetic difference for cox1, supporting their placement together but separation as distinct taxa. Using infection frequencies, M. pacificae, like its sister species P. mytili, does not interact with Ancistrum spp., co-inhabitants of the mantle cavity. On the basis of these ecological similarities, the fossil record of host mussels, and features of morphology and stomatogenesis of these two ciliates, we argue that M. pacificae derived from a Peniculistoma-like ancestor after divergence of the two host mussels. Our phylogenetic analyses of pleuronematid ciliates includes the SSUrRNA gene sequence of Sulcigera comosa, a Histiobalantium-like ciliate from Lake Baikal. We conclude: (i) that the pleuronematids are a monophyletic group; (ii) that the genus Pleuronema is paraphyletic; and (iii) that S. comosa is a Histiobalantium species. We transfer S. comosa to Histiobalantium and propose a new combination Histiobalantium comosa n. comb.
authors.affiliation: Department of Biology, San Francisco State University, San Francisco, California, 94132, USA.
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Antipa
authors.affiliation: Sorbonne Universités, UPMC Univ. Paris 06, UMR 7093, Laboratoire d'Océanographie de Villefranche, Villefranche-sur-Mer, 06230, France.|CNRS, UMR 7093, B.P. 28, Station Zoologique, Laboratoire d'Océanographie de Villefranche, Villefranche-sur-Mer, 06230, France.
authors.forename: John R
authors.initials: JR
authors.lastname: Dolan
authors.affiliation: Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada.
authors.forename: Denis H
authors.initials: DH
authors.lastname: Lynn
authors.affiliation: Limnological Institute of the Siberian Branch, Russian Academy of Sciences, Ulan-Batorskaya Str. 3, Irkutsk 664033, Russia.
authors.forename: Lubov A
authors.initials: LA
authors.lastname: Obolkina
authors.affiliation: Department of Integrative Biology, University of Guelph, Guelph, ON, N1G 2W1, Canada.
authors.forename: Michaela C
authors.initials: MC
authors.lastname: Strüder-Kypke
mesh_terms: D000818:Animals; D001483:Base Sequence; D049872:Bivalvia / Q000469:parasitology*; D002140:California; D016798:Ciliophora / Q000145:classification* / Q000166:cytology / Q000235:genetics* / Q000502:physiology; D002965:Classification; D016054:DNA, Protozoan / Q000235:genetics; D004463:Ecology; D019143:Evolution, Molecular; D020459:Genes, rRNA / Q000235:genetics; D016802:Oligohymenophorea / Q000145:classification* / Q000166:cytology / Q000235:genetics* / Q000502:physiology; D010802:Phylogeny; D012335:RNA, Ribosomal / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
chemical_list: D016054:DNA, Protozoan; D012335:RNA, Ribosomal
keywords: Cytochrome c oxidase subunit 1; Mytilophilus pacificae; Mytilus californianus; Mytilus edulis; Peniculistoma mytili; scuticociliate