title: Morphology, ultrastructure, and molecular phylogeny of the ciliate Sonderia vorax with insights into the systematics of order Plagiopylida.
abstract: BACKGROUND
  Ciliates of the family Sonderiidae are common members of the eukaryotic communities in various anoxic environments. They host both ecto- and endosymbiotic prokaryotes (the latter associated with hydrogenosomes) and possess peculiar morpho-ultrastructural features, whose functions and homologies are not known. Their phylogenetic relationships with other ciliates are not completely resolved and the available literature, especially concerning electron microscopy and molecular studies, is quite scarce.
  
  
  RESULTS
  Sonderia vorax Kahl, 1928 is redescribed from an oxygen-deficient, brackish-water pond along the Ligurian Sea coastlines of Italy. Data on morphology, morphometry, and ultrastructure are reported. S. vorax is ovoid-ellipsoid in shape, dorsoventrally flattened, 130 x 69 μm (mean in vivo); it shows an almost spherical macronucleus, and one relatively large micronucleus. The ventral kinetom has a "secant system" including fronto-ventral and fronto-lateral kineties. A distinctive layer of bacteria laying between kineties covers the ciliate surface. Two types of extrusomes and hydrogenosomes-endosymbiotic bacteria assemblages are present in the cytoplasm. The phylogeny based on 18S rRNA gene sequences places S. vorax among Plagiopylida; Sonderiidae clusters with Plagiopylidae, although lower-level relationships remain uncertain. The studied population is fixed as neotype and the ciliate is established as type species of the genus, currently lacking.
  
  
  CONCLUSIONS
  This is the first description of a representative of Sonderiidae performed with both morphological and molecular data. To sum up, many previous hypotheses on this interesting, poorly known taxon are confirmed but confusion and contradictory data are as well highlighted.
authors: Unit of Protistology-Zoology, Department of Biology, University of Pisa, Pisa 56126, Italy. lmodeo@biologia.unipi.it
authors: Letizia
authors: L
authors: Modeo
authors: Sergei I
authors: SI
authors: Fokin
authors: Vittorio
authors: V
authors: Boscaro
authors: Ilaria
authors: I
authors: Andreoli
authors: Filippo
authors: F
authors: Ferrantini
authors: Giovanna
authors: G
authors: Rosati
authors: Franco
authors: F
authors: Verni
authors: Giulio
authors: G
authors: Petroni
mesh_terms: D016798:Ciliophora / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification / Q000648:ultrastructure*; D016000:Cluster Analysis; D016054:DNA, Protozoan / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D020459:Genes, rRNA; D007558:Italy; D008853:Microscopy; D008969:Molecular Sequence Data; D015388:Organelles / Q000648:ultrastructure; D010802:Phylogeny; D016053:RNA, Protozoan / Q000235:genetics; D012337:RNA, Ribosomal, 18S / Q000235:genetics; D012623:Seawater / Q000469:parasitology; D017422:Sequence Analysis, DNA
chemical_list: D016054:DNA, Protozoan; D004275:DNA, Ribosomal; D016053:RNA, Protozoan; D012337:RNA, Ribosomal, 18S