Among nudibranch molluscs, the family Tritoniidae gathers taxa with unclear phylogenetic position, such as some species of the genus Tritonia Cuvier, 1798. Currently, 35 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 and T. dantarti, being widely-spread in the Southern Ocean, and endemic to Bouvet Island, respectively. Coloration seemed 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, thus, we suggest the resurrection of T. antarctica Martens & Pfeffer, 1886 to encompass exclusively the Antarctic species. To progress further, additional molecular data from Magellanic specimens are required to definitely resolve their taxonomy and systematics. Key words: Phylogenetic analyses, Southern Ocean, species delimitation tests, Tritoniidae taxonomy.

中文翻译：

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橙色是新的白色：南极Tritonia物种的分类学修订（Gastropoda：Nudibranchia）

在裸udi科软体动物中，Tritoniidae科收集的系统发育位置不清楚的类群，例如Tritonia Cuvier属的一些物种，1798年。目前，该属有35个有效物种，在南大洋中仅发现了3个物种，即T。 Challengeriana Bergh，1884年； T。dantarti Ballesteros和Avila，2006年； T。vorax（Odhner，1926年）。在这项研究中，我们阐明了使用形态解剖和分子技术对南极Tritonia物种进行的长期讨论的系统分类学。解剖来自韦德尔海和布韦岛的样品，并准备进行扫描电子显微镜检查。通过最大似然法和贝叶斯方法对三种分子标记COI，16S和H3进行了测序和分析。系统发育分析和物种定界测试清楚地区分了两个物种T. Challengeriana和T. dantarti在南大洋广泛传播，分别是布韦岛特有的。由于分子数据显示两个物种都可能具有橙色或白色的颜色形态，因此在物种间进行区分似乎是不可靠的特征。这种变异性可以通过它们所捕食的软珊瑚物种的色素螯合来解释。形态学分析揭示了南极挑战虫的南极和麦哲伦标本之间的差异，因此，我们建议复活南极扩张虫的Martens＆Pfeffer，1886年仅涵盖南极物种。为了进一步发展，需要从麦哲伦（Magellanic）标本中获得更多分子数据，以明确解决其分类学和系统学问题。关键词：系统发育分析，南大洋，物种划界测试，