Predation by the nudibranch Tritonia odhneri (Opisthobranchia: Tritoniidae) on octocorals from the South Atlantic Ocean
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ORIGINAL PAPER
Predation by the nudibranch Tritonia odhneri (Opisthobranchia: Tritoniidae) on octocorals from the South Atlantic Ocean Stella García-Matucheski & Claudia Muniain
Received: 13 April 2010 / Revised: 12 September 2010 / Accepted: 13 October 2010 / Published online: 31 October 2010 # Senckenberg, Gesellschaft für Naturforschung and Springer 2010
Abstract The diet of the nudibranch mollusc Tritonia odhneri was investigated for the first time based on a detailed anatomical analysis of the gut content of 52 specimens. Digestive tracts of specimens were analysed under stereoscopic microscope equipped with digital camera. Portions of octocorals containing the calcareous sclerites were removed from the tracts and prepared for scanning electron microscopy (SEM). Sclerite morphology and size were determined at the species and genus level on the basis of a taxonomical revision and compared with fresh octocoral specimens collected from Patagonia (San Jorge Gulf) and with voucher specimens from the collections of Museo Argentino de Ciencias Naturales (MACN-in). Specific predation of T. odhneri on octocoral species present in the southwestern Atlantic Ocean was detected. The nudibranch feeds on the gorgonians Primnoella divaricata, Primnoella scotiae (=P. compressa) and Tripalea clavaria, and the pennatulaceans Renilla octodentata and Stylatula sp. A world checklist of dietary interactions between species of the genus Tritonia and octocorals is presented and discussed. Keywords Sclerites . Diet . Predation . Tritonia odhneri . Octocoral
S. García-Matucheski : C. Muniain (*) Lab. Ecología Química y Biodiversidad Acuática. Instituto de Investigación e Ingeniería Ambiental, Universidad Nacional de San Martín, Peatonal Belgrano 3563 1° (1650), San Martín, Buenos Aires, Argentina e-mail: [email protected]
Introduction The members of the family Tritoniidae feed on octocorals, including sea pens, alcyonarian soft corals and gorgonians; they are sometimes cryptic upon their prey species, mimicking them in shape and coloration (McDonald and Nybakken 1996, 1999; Avila et al. 1999; Smith and Gosliner 2003, 2005, 2007; Wyeth et al. 2006; Debelius and Kuiter 2007). An exception is a recently described species, Tritonia papalotla Bertsch et al. 2009, feeding on a zoanthid anthozoan (Bertsch et al. 2009). Gorgonians are octocorals characterised by a tough but flexible axis composed of the scleroprotein gorgonin, with varying amounts of calcareous material included in the axis as well as in the living tissue where the calcareous structures take the form of sclerites. Sclerite morphology is used for identification to species level (Bayer 1955; Bayer et al. 1983). Systematic reviews of octocorals from the southwestern Atlantic are scarce and outdated, hindering taxonomic identification of the species studied (Bayer 1961; Verseveldt 1967; Zamponi and Pérez 1995, 1996; Barreira e Castro and Semeraro de Medeiros 2001; Zamponi 2001; Pérez and Zamponi 2004; Cairns 2006). Tritonia odhneri Marcus 1959 is a conspicuous, largesized (2
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