Orange is the new white: taxonomic revision of Tritonia species (Gastropoda: Nudibranchia) from the Weddell Sea and Bouvet Island

Abstract Among nudibranch molluscs, the family Tritoniidae gathers taxa with an uncertain phylogenetic position, such as some species of the genus Tritonia Cuvier, 1798. Currently, 37 valid species belong to this genus and only three of them are found in the Southern Ocean, namely T. challengeriana...

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Bibliographic Details
Published in:Polar Biology
Main Authors: Rossi, Maria Eleonora, Avila, Conxita, Moles, Juan
Other Authors: Ministerio de Ciencia, Innovación y Universidades, Sapienza Università di Roma
Format: Article in Journal/Newspaper
Language:English
Published: Springer Science and Business Media LLC 2021
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Online Access:http://dx.doi.org/10.1007/s00300-021-02813-8
http://link.springer.com/content/pdf/10.1007/s00300-021-02813-8.pdf
http://link.springer.com/article/10.1007/s00300-021-02813-8/fulltext.html
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Summary:Abstract Among nudibranch molluscs, the family Tritoniidae gathers taxa with an uncertain phylogenetic position, such as some species of the genus Tritonia Cuvier, 1798. Currently, 37 valid species belong to this genus and only three of them are found in the Southern Ocean, namely T. challengeriana Bergh, 1884, T. dantarti Ballesteros & Avila, 2006, and T. vorax (Odhner, 1926). In this study, we shed light on the long-term discussed systematics and taxonomy of Antarctic Tritonia species using morpho-anatomical and molecular techniques. Samples from the Weddell Sea and Bouvet Island were dissected and prepared for scanning electron microscopy. The three molecular markers COI, 16S, and H3 were sequenced and analysed through maximum-likelihood and Bayesian methods. The phylogenetic analyses and species delimitation tests clearly distinguished two species, T. challengeriana widely spread in the Southern Ocean and T. dantarti endemic to Bouvet Island . Colouration seems to be an unreliable character to differentiate among species since molecular data revealed both species can either have orange or white colour morphotypes. This variability could be explained by pigment sequestration from the soft coral species they feed on. Morphological analyses reveal differences between Antarctic and Magellanic specimens of T. challengeriana. However, the relationship between T. challengeriana specimens from these two regions remains still unclear due to the lack of molecular data. Therefore, the validity of the T. antarctica Martens & Pfeffer, 1886, exclusively found in Antarctic waters requires further systematic work.