Increased information on biodiversity from the neglected part of the North Pacific contributes to the understanding of phylogeny and taxonomy of nudibranch molluscs

Understanding of the biological diversity, involving molecular phylogenetic methods, is a fundamental task for a broad array of evolutionary, taxonomic, and ecological studies, as well as a basis for conservation. Our hydrobiological survey during an expedition in 2021 to the coastal waters of the Kuril Islands (the northwestern Pacific) revealed the undocumented diversity of the nudibranch molluscs. Two new species of the genera Zelentia and Cuthonella are described here using analysis of fine-scale morphological and molecular data. Representatives of the genus Zelentia prior to this study were known only from the North Atlantic and from the Canadian and US northeastern Pacific. In addition, two new distributional records of the previously described species Cuthonella denbei Korshunova et al., 2020 and Cuthonella soboli Martynov, 1992 are presented here for the first time. The molecular phylogenetic framework for the majority of the species of the genera Cuthonella and Zelentia, including the two new species, confirmed the taxonomic distinctness of the genus Zelentia (family Trinchesiidae) and the genus Cuthonella (family Cuthonellidae), and represents another important result of this study. Key words: biodiversity, Cuthonella, North Pacific, nudibranch molluscs, molecular phylogeny, phylogeography, Zelentia La comprehension de la diversite biologique, notamment par des methodes de phylogenetique moleculaire, constitue une tache fondamentale d'une vaste gamme d'etudes taxonomiques, ecologiques et de l'evolution, ainsi qu'un fondement de la conservation. Un leve hydrobiologique realise durant une expedition en 2021 dans les eaux littorales des Kouriles (nord-ouest de l'ocean Pacifique) revele une diversite non documentee de mollusques nudibranches. Deux nouvelles especes des genres Zelentia et Cuthonella sont decrites en utilisant une analyse de donnees moleculaires et morphologiques fines. Des representants du genre Zelentia n'etaient auparavant connus que de l'Amerique du Nord et des eaux canadiennes et etats-uniennes du nordest de l'ocean Pacifique. En outre, deux nouveaux cas de presence des especes deja decrites Cuthonella denbei Korshunova et al., 2020 et Cuthonella soboli Martynov, 1992 qui elargissent leurs aires de repartition respectives, sont presentes pour la premiere fois. Le cadre phylogenetique moleculaire pour la majorite des especes des genres Cuthonella et Zelentia, incluant deux nouvelles especes, confirme le caractere distinct sur le plan taxonomique du genre Zelentia (famille des trinchesiides) et du genre Cuthonella (famille des cuthonellides) et constitue un autre important resultat de la presente etude. [Traduit par la Redaction] Mots-cles : biodiversite, Cuthonella, Pacifique Nord, mollusques nudibranches, phylogenetique moleculaire, phylogeographie, Zelentia
Introduction The Kuril Islands are scientifically and economically an important chain of over 50 volcanic islands in the northwestern Pacific with diverse fauna and flora (e.g., Kotlyakov et al. 2009; [...]