Two new species and a remarkable record of the genus Dendronotus from the North Pacific and Arctic oceans (Nudibranchia)

Similar Ones Are Not Related and Vice Versa—New Dendronotus Taxa (Nudibranchia: Dendronotidae) from the North Atlantic Ocean Provide a Platform for Discussion of Global Marine Biodiversity Patterns

One new species of the genus Dendronotus (Nudibranchia: Dendronotidae) is described from Norway and Northern Ireland, as well as from the adjacent North Sea, and one new subspecies of Dendronotus arcticus is described from Norway by applying a combination of fine-scale morphological and molecular phylogenetic data. The present case demonstrates multilevel morphological and molecular similarities and differences considering on the one hand a grouping of three similar looking sympatric taxa (D. yrjargul, D. arcticus gartensis n. subsp. and D. keatleyae n. sp.), and on the other hand two different looking apparently allopatric subspecies (D. arcticus arcticus and D. arcticus gartensis n. subsp.). The type species of the genus, D. frondosus, which is the commonest dendronotid in Norway and the United Kingdom, consistently demonstrates substantial molecular and fine-scale morphological differences from D. keatleyae n. sp. The present study, apart from providing purely taxonomic information, also provides new data for a broad discussion of global biodiversity patterns.

A 50-year conundrum is conclusively solved: nudibranchs Dendronotus albus (= D. diversicolor) and Dendronotus robilliardi are valid species with compelling evidence from type materials, bibliographic sources, and molecular data

A persistent confusion in the identification of two similar species of nudibranch molluscs of the genus Dendronotus Alder and Hancock, 1845, which inhabit shallow Canadian, Russian, and US waters of the northern Pacific Ocean, has caused a considerable taxonomic conundrum for over 50 years. In this study, we present compelling evidence for the first time, including morphological and molecular data as well as a study of type materials, to definitively conclude that Dendronotus albus MacFarland, 1966 was misidentified in the publication of G.A. Robilliard (1970; Veliger, 12: 433–479). This caused the long-term incorrect application of the characters of the real D. albus sensu F.M. MacFarland (1966; Mem. Calif. Acad. Sci. 6: 1–546) (which is still circulated in the literature) to a completely different, though externally similar, species incorrectly named “D. albus” in G.A. Robilliard (1970; Veliger, 12: 433–479). This species was properly described only 3 years ago as Dendronotus robilliardi Korshunova, Sanamyan, Zimina, Fletcher and Martynov, 2016. Using multiple evidence in this study, we firmly conclude that D. robilliardi is a well-supported valid species, whereas “Dendronotus diversicolor” Robilliard, 1970 is a junior synonym of D. albus. We also present rare bibliographic materials that shed light on the source of the misidentification of these species and also confirm the designation of the lectotype for D. albus. Biogeographical data, which are important for conservation and ecological studies, are also presented for D. albus and D. robilliardi in the Canadian and American Pacific Ocean.

The Emperor’s Cadlina, hidden diversity and gill cavity evolution: new insights for the taxonomy and phylogeny of dorid nudibranchs (Mollusca: Gastropoda)

Dorids are one of the largest nudibranch groups, encompassing more than 2000 species. One of the crucial problems with tracing the evolution of dorids is the relationship between cryptobranch dorids (gill cavity present) and phanerobranch dorids (gill cavity absent). Integrative morphological and molecular studies of the enigmatic Japanese dorid species of the cryptobranch genus Cadlina, C. japonica and ‘C.’ sagamiensis, which were collected by the Emperor of Japan (Shōwa era), are presented here for the first time. It is shown that while C. japonica does belong to the Cadlina clade, another Japanese species ‘C.’ sagamiensis is not part of the cryptobranch dorids of the family Cadlinidae, but is related to both the phanerobranch dorid family, Hexabranchidae, and to the cryptobranch family Cadlinellidae stat. nov. A new genus, Showajidaia gen. nov., and new family, Showajidaiidae fam. nov., are proposed for ‘C.’ sagamiensis, and four new species of the genus Cadlina are described based on a dorid-wide molecular phylogenetic analysis, which is the first substantial update of the dorid family system since 2010. Integration of phylogenetic data with an ontogenetic model of dorid evolution suggests that cryptobranch organization can be most reliably assessed as the ancestral state for the majority of dorids.

Diet-driven ecological radiation and allopatric speciation result in high species diversity in a temperate-cold water marine genus Dendronotus (Gastropoda: Nudibranchia)

While the majority nudibranch clades are more species rich in the tropics, the genus Dendronotus is mainly represented in Arctic and boreal regions. This distribution pattern remains poorly understood. An integrative approach and novel data provided valuable insights into processes driving Dendronotus radiation and speciation. We propose an evolutionary scenario based on molecular phylogenetics and morphological, ecological, ontogenetic data, combined with data on complex geology and paleoclimatology of this region. Estimated phylogenetic relationships based on four molecular markers (COI, 16S, H3 and 28S) shows strong correlation with radular morphology, diet and biogeographical pattern. Ancestral area reconstruction (AAR) provides evidence for a tropical Pacific origin of the genus. Based on AAR and divergence time estimates we conclude that the evolution of Dendronotus has been shaped by different processes: initial migration out of the tropics, diet-driven adaptive radiation in the North Pacific influenced by Miocene climate change, and subsequent allopatric speciation resulting from successive closings of the Bering strait and cooling of the Arctic Ocean during the Pliocene-Pleistocene. At the same time, contemporary amphiboreal species appear to have dispersed into the Atlantic fairly recently.

"Noah's Ark" Project: Interim Results and Outlook for Classic Collection Development

The "Noah's Ark" project, afoot at M.V. Lomonosov Moscow State University since 2015 and aimed at studying biodiversity, is the largest ongoing Russian project in life sciences. During its implementation, several hundred new species have been described; a comprehensive genetic and biochemical characterization of these species, as well as that of the pre-existing specimens in Moscow University's collections, has been performed. A consolidated IT system intended to house the knowledge generated by the project has been developed. Here, we summarize the investigations around the Moscow University classical biocollections which have taken place within the framework of the project and discuss future promise and the outlook for these collections.

Morphological and molecular evidence indicate Dendronotus primorjensis is a valid species that has priority over D. dudkai (Nudibranchia)

Morphological and molecular data of type material of the nudibranch mollusc Dendronotus primorjensis Martynov, Sanamyan, Korshunova, 2015 from the Sea of Japan are summarised and compared with those of Dendronotus dudkai Ekimova, Schepetov, Chichvarkhina, Chichvarkhin, 2016. The clear conclusion is that the latter is a junior synonym of Dendronotus primorjensis.