M Antonio Todaro1, Matteo Dal Zotto2, Francesca Leasi3. 1. Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy. 2. Department of Life Sciences, University of Modena and Reggio Emilia, Modena, Italy; Consorzio Interuniversitario per il Centro di Biologia Marina ed Ecologia Applicata 'G. Bacci', Livorno, Italy. 3. National Museum of Natural History, Smithsonian Institution, Washington, D.C., United States of America.
Abstract
BACKGROUND: Gastrotricha systematics is in a state of flux mainly due to the conflicts between cladistic studies base on molecular markers and the classical systematisation based on morphological traits. In sandy samples from Thailand, we found numerous macrodasyidan gastrotrichs belonging to an undescribed species of difficult taxonomic affiliation. The abundance and original nature of the specimens prompted us to undertake a deep survey of both morphological and molecular traits aiming at a reliable systematisation of the new taxon. METHODOLOGY/PRINCIPAL FINDINGS: Using several microscopical techniques we investigated the external and internal anatomy, including the muscular and nervous systems of the new species. Additional specimens were used to obtain the 18S rRNA gene sequence; molecular data was analysed cladistically in conjunction with data from additional species belonging to the near complete Macrodasyida taxonomic spectrum. Specimens are vermiform, up to 806 μm in total length, and show a well-defined head equipped with peculiar leaf-like sensorial organs and a single-lobed posterior end. The adhesive apparatus includes anterior, ventrolateral, dorsal and posterior tubes. Pharynx is about 1/4 of the total length and shows pores at its posterior 3/4. Adult specimens exhibit maturing eggs and a bulky, muscular caudal organ, but do not show sperm nor the frontal organ. Musculature and nervous system organisation resemble the usual macrodasyidan plan; however, the somatic circular muscles of the intestinal region surround all other muscular components and a third FMRFamide-IR commissure ventral to the pharyngo-intestinal junction appear to be an autoapomorphic traits of the new species. CONCLUSIONS/SIGNIFICANCE: While the anatomical characteristics of the Asian specimens appear so unique to grant the establishment of a new taxon, for which the name Thaidasys tongiorgii gen. et sp. nov. is proposed, the result of phylogenetic analyses based on the 18S rRNA gene unites the new genus with the family Macrodasyidae.
BACKGROUND: Gastrotricha systematics is in a state of flux mainly due to the conflicts between cladistic studies base on molecular markers and the classical systematisation based on morphological traits. In sandy samples from Thailand, we found numerous macrodasyidan gastrotrichs belonging to an undescribed species of difficult taxonomic affiliation. The abundance and original nature of the specimens prompted us to undertake a deep survey of both morphological and molecular traits aiming at a reliable systematisation of the new taxon. METHODOLOGY/PRINCIPAL FINDINGS: Using several microscopical techniques we investigated the external and internal anatomy, including the muscular and nervous systems of the new species. Additional specimens were used to obtain the 18S rRNA gene sequence; molecular data was analysed cladistically in conjunction with data from additional species belonging to the near complete Macrodasyida taxonomic spectrum. Specimens are vermiform, up to 806 μm in total length, and show a well-defined head equipped with peculiar leaf-like sensorial organs and a single-lobed posterior end. The adhesive apparatus includes anterior, ventrolateral, dorsal and posterior tubes. Pharynx is about 1/4 of the total length and shows pores at its posterior 3/4. Adult specimens exhibit maturing eggs and a bulky, muscular caudal organ, but do not show sperm nor the frontal organ. Musculature and nervous system organisation resemble the usual macrodasyidan plan; however, the somatic circular muscles of the intestinal region surround all other muscular components and a third FMRFamide-IR commissure ventral to the pharyngo-intestinal junction appear to be an autoapomorphic traits of the new species. CONCLUSIONS/SIGNIFICANCE: While the anatomical characteristics of the Asian specimens appear so unique to grant the establishment of a new taxon, for which the name Thaidasys tongiorgii gen. et sp. nov. is proposed, the result of phylogenetic analyses based on the 18S rRNA gene unites the new genus with the family Macrodasyidae.
Authors: Ward Appeltans; Shane T Ahyong; Gary Anderson; Martin V Angel; Tom Artois; Nicolas Bailly; Roger Bamber; Anthony Barber; Ilse Bartsch; Annalisa Berta; Magdalena Błażewicz-Paszkowycz; Phil Bock; Geoff Boxshall; Christopher B Boyko; Simone Nunes Brandão; Rod A Bray; Niel L Bruce; Stephen D Cairns; Tin-Yam Chan; Lanna Cheng; Allen G Collins; Thomas Cribb; Marco Curini-Galletti; Farid Dahdouh-Guebas; Peter J F Davie; Michael N Dawson; Olivier De Clerck; Wim Decock; Sammy De Grave; Nicole J de Voogd; Daryl P Domning; Christian C Emig; Christer Erséus; William Eschmeyer; Kristian Fauchald; Daphne G Fautin; Stephen W Feist; Charles H J M Fransen; Hidetaka Furuya; Oscar Garcia-Alvarez; Sarah Gerken; David Gibson; Arjan Gittenberger; Serge Gofas; Liza Gómez-Daglio; Dennis P Gordon; Michael D Guiry; Francisco Hernandez; Bert W Hoeksema; Russell R Hopcroft; Damià Jaume; Paul Kirk; Nico Koedam; Stefan Koenemann; Jürgen B Kolb; Reinhardt M Kristensen; Andreas Kroh; Gretchen Lambert; David B Lazarus; Rafael Lemaitre; Matt Longshaw; Jim Lowry; Enrique Macpherson; Laurence P Madin; Christopher Mah; Gill Mapstone; Patsy A McLaughlin; Jan Mees; Kenneth Meland; Charles G Messing; Claudia E Mills; Tina N Molodtsova; Rich Mooi; Birger Neuhaus; Peter K L Ng; Claus Nielsen; Jon Norenburg; Dennis M Opresko; Masayuki Osawa; Gustav Paulay; William Perrin; John F Pilger; Gary C B Poore; Phil Pugh; Geoffrey B Read; James D Reimer; Marc Rius; Rosana M Rocha; José I Saiz-Salinas; Victor Scarabino; Bernd Schierwater; Andreas Schmidt-Rhaesa; Kareen E Schnabel; Marilyn Schotte; Peter Schuchert; Enrico Schwabe; Hendrik Segers; Caryn Self-Sullivan; Noa Shenkar; Volker Siegel; Wolfgang Sterrer; Sabine Stöhr; Billie Swalla; Mark L Tasker; Erik V Thuesen; Tarmo Timm; M Antonio Todaro; Xavier Turon; Seth Tyler; Peter Uetz; Jacob van der Land; Bart Vanhoorne; Leen P van Ofwegen; Rob W M van Soest; Jan Vanaverbeke; Genefor Walker-Smith; T Chad Walter; Alan Warren; Gary C Williams; Simon P Wilson; Mark J Costello Journal: Curr Biol Date: 2012-11-15 Impact factor: 10.834
Authors: M Antonio Todaro; Matteo Dal Zotto; Ulf Jondelius; Rick Hochberg; William D Hummon; Tobias Kånneby; Carlos E F Rocha Journal: PLoS One Date: 2012-02-14 Impact factor: 3.240
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