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Crossing the polar front—Antarctic species discovery in the nudibranch genus Tritoniella (Gastropoda)

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Tritoniella belli is the only valid species of a nudibranch genus endemic to the Southern Ocean. Recent exhaustive sampling and molecular analyses led to the discovery of several new lineages. A total of 69 specimens were collected from 25 sites across the Weddell and Scotia Seas, from 5 to 751 m depth. In this study, we provide morphological and anatomical characters to describe five new Tritoniella species, namely T. gnocchi n. sp., T. prinzess n. sp., T. gnathodentata n. sp., T. schoriesi n. sp., T. heideae n. sp. Detailed descriptions of colouration, external morphology, digestive and reproductive organs, distribution, and ecology are presented in a systematic context. These are compared to the type material from the Ross Sea of T. belli and its synonym T. sinuata, whose status requires additional sampling to be solved. Discrete differences in external characters, including the shape of dorsal notum ridge and mantle edges, support the species hypotheses delimited by Moles, Berning et al. (2021). Moreover, detailed scanning electron microscopy images of the masticatory border of the jaws, radula teeth, and penial papilla were provided and their differences discussed. The gut content of all species revealed sclerites of Primnoidae gorgonians as their preferred prey. Pseudo-cryptic radiations along the Scotia Arc, explained by the combination of distribution reduction due to glacial cycles and the existence of refugia, and enhanced by their direct development, could explain the allopatric speciation events in Tritoniella species.

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Availability of data and material

Material examined during this study including type material is deposited at the SNSB-Bavarian State Collection of Zoology (ZSM, Munich, DE) and the Benthic Invertebrate Collection at Scripps Institution of Oceanography (SIO-BIC, La Jolla, CA, USA).

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We would like to thank the crews and science parties on the R/V Polarstern (AWI, Germany) during the EASIZ II and the 2000 cruises, and of the R/V Nathaniel B. Palmer (NSF, USA) during the 2011 and 2013 cruises. Special thanks go to Amy Moran (UH, Manao) and Peter Brueggeman for providing live pictures of T. belli specimens and to Greg Rouse (SIO, UCSD) for field support and photography. We appreciate Andreia Salvador (NHM, UK) and Charlotte Seid (BIC-SIO, USA) for helping provide type and specimen material. Many thanks go to Heike Wägele (ZFMK, Germany) for providing valuable information on her previous work. We thank Dirk Schories (DLR, Germany) for providing specimens and live pictures from his SCUBA-dives and Roland Melzer (ZSM, Germany) for helping with the SEM imaging. Additional thanks go to Irina Ekimova (MSU, Russia) for providing us with the elusive Minichev (1972) publication. Special thanks go to Morgan Oberweiser (LMU, Germany) for proofreading the draft before submission. We also thank all people involved in providing low-cost, open-access, and open-source software. Two anonymous reviewers provided comments that helped improve this paper. JM postdoctoral fellowship and microscopy analyses were supported by the Alexander von Humboldt Foundation (Germany). Funds for field research and sequencing were provided by the German Research Foundation (DFG SCHR667/3,4,15 to MS) and National Science Foundation, USA (ANT-1043749 to NGW).


JM postdoctoral fellowship and microscopy analyses were supported by the Alexander von Humboldt Foundation (Germany). Funds for field research were provided by the German Research Foundation (DFG SCHR667/3,4,15 to MS) and National Science Foundation, USA (ANT-1043749 to NGW).

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MS and NGW collected specimens. MS and JM contributed to resources and work in the conceptualization. PMS and JM performed laboratory work and wrote the original draft. All authors reviewed and edited the final version of the manuscript.

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Correspondence to Peter M. Schächinger.

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Schächinger, P.M., Schrödl, M., Wilson, N.G. et al. Crossing the polar front—Antarctic species discovery in the nudibranch genus Tritoniella (Gastropoda). Org Divers Evol 22, 431–456 (2022).

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