Dendronotus nordenskioeldi, Korshunova & Bakken & GrØtan & Johnson & Lundin & Martynov, 2021

Korshunova, Tatiana, Bakken, Torkild, GrØtan, Viktor V., Johnson, Kjetil B., Lundin, Kennet & Martynov, Alexander, 2021, A synoptic review of the family Dendronotidae (Mollusca: Nudibranchia): a multilevel organismal diversity approach, Contributions to Zoology 90 (1), pp. 93-153 : 104-106

Dendronotus nordenskioeldi sp. nov.

Figs 1–3 , 5–7

ZooBank: http:// urn:lsid:zoobank.org:act:9FB63088-BF8A-4990-B292-7E26DEA0FDCF

Etymology. In honour of Baron Nils Adolf Erik Nordenskiöld, outstanding Arctic explorer, geologist, and mineralogist. The Laptev Sea

had been originally named “Nordenskiöld Sea”, after this Arctic explorer.

Type locality. Laptev Sea.

Type material. Holotype. ZMMU Op-665. Arctic region, Laptev Sea, sta. 100, 69 m depth, collector Olga Zimina .

Description. Body relatively narrow, preserved holotype 19 mm length (fig. 5). Fiveto six main branched appendages on oral veil. Five appendages on rhinophoral stalks; 12–14 rhinophoral lamellae. Lateral papilla on rhinophoral sheath present. Five pairs of dorsolateral appendages. Circa 20 lip papillae. Dorsolateral appendages with relatively short primary stalk, moderately branched secondary branchesandtertiarybranches (fig. 5A, B). Basal colour is semitranslucent white. No additional pigment. Dorsal processes of jaws inclined posteriorly at approximately 53° to the longitudinal axis of the jaw body and 0.42 of its length (fig. 5D). Masticatory border of jaw with fine denticles (fig. 5E). Radular formula: 43 × 3– 11.1.11 –3. Central (rachidian) tooth bears very weak denticulation that are difficult to separate into individual denticles (up to 20 and more variously varied denticles at least) (fig. 5F, G). Denticles without deep furrows.Lateralteeth elongate, slightly curved, bearing up to seven denticles (+ 2–3 reduced denticles may present) (fig. 4F–H). Ampulla thickened, kidney-shaped. Prostate discoidal, consisting of up to 20 alveolar glands. Distal part of vas deferens moderate in length, transitioning to long, thick, curved copulatory organ. Bursa copulatrix large, distinctly elongated, with seminal receptaculum placed distally.

Distribution. So far known only from the Laptev Sea.

Remarks. Externally, Dendronotus nordenskioeldi sp. nov. resembles white forms of D. lacteus but differs by the absence of a distinct

reticulation and peculiar ribs on the central teeth, which is a common characteristic of D. lacteus ( Korshunova et al., 2017a) . According

to the molecular differences, a minimal intergroup distance for the COI gene (7.9%) is found between D. nordenskioeldi sp. nov and D. europaeus . The mean intergroup distances between D. nordenskioeldi sp. nov. and D. rufus , D. lacteus , and D. kamchaticus are 8.3%, 8.3%, and 8.8% respectively. Amaximal intergroup distance (15.0%) is found between D. nordenskioeldi sp. nov and D. patricki (Appendix, table A2 ).

Synopsis of the previously described valid taxa of the family Dendronotidae

Figures

FIGURE 1 Phylogenetic relationships of the species of the genus Dendronotus based on COI + 16S + 28S + H3 concatenated dataset inferred by Bayesian Inference (BI). Numbers represent posterior probabilities from BI and bootstrap values for Maximum Likelihood.Some branches are collapsed at species level.Dendronotus elegans from the type region (North Atlantic) are highlighted in dark purple. Abbreviations:h – holotype; p – paratype.Summary of species delimitation results from ABGD analyses for the COI dataset is shown

FIGURE 2 Phylogenetic relationships of the species of the genera Dendronotus, Pseudobornella and Cabangus in single COI, 16S, 28S, and H3 gene trees inferred by Bayesian Inference (BI). Some branches are collapsed. Positions the Pseudobornella orientalis highlighted green; positions the Cabangus regius highlighted orange.Numbers represent posterior probabilities from BI. PHOTOGRAPHS BY A. MARTYNOV AND T. KORSHUNOVA

FIGURE 3 A.Map of the Northern Hemisphere showing the distribution of D.elegans (including “D.niveus”), D.kalikal, and D.yrjargul sp. nov.The type locality of D.elegans is indicated by crossed lines. B. The haplotype networks based on cytochrome c oxidase subunit I (COI), 16S rRNA (16S), and 28S rRNA (28S) molecular data showing genetic mutations occurring within D.elegans (“D.niveus”), D. kalikal, and D.yrjargul sp. nov. specimens.Abbreviations:BeSt – Bering Strait; BS – Barents Sea; Gr – Greenland; Km – Kamchatka; KS – Kara Sea; Ku – Kuril Islands; LS – Laptev Sea; Nf – Newfoundland; NS – Norwegian Sea; WS – White Sea.Type locality of D.elegans is marked on the map by “x”.

FIGURE 5 Dendronotus nordenskioeldi sp. nov.ZMMU Op-665, external and internal morphology.a–b:living holotype, dorsal and lateral views respectively;c:ventral view of preserved holotype;d: jaw of holotype; e: irregular denticles on the masticatory edge of the holotype;f:posterior part of radula; g:central teeth of radula; h: lateral teeth of radula of holotype.Scale bars: d: 1mm; e: 20 µm; f:100 µm; g, h: 30 µm. PHOTOGRAPHS BY O. ZIMINA (A, B) AND T. KORSHUNOVA (C). SEM MICROGRAPHS BY A. MARTYNOV

FIGURE 6 Reproductive systems. a, Dendronotus yrjargul sp. nov.; b, D.kalikal; c, D.elegans; d, D. nordenskioeldi sp. nov. Scale bars:a–d 1mm.Abbreviations:am, ampulla; bc, bursa copulatrix; fgm, female gland mass; fo, female opening; p, penis; pr, prostate; rs, receptaculum seminis; ud, uterine duct; vd, vas deferens; vg, vaginal duct.

FIGURE 7 Representaives of the genus Dendronotus (living specimens). PHOTOGRAPHS BY T. KORSHUNOVA, A. MARTYNOV, K. FLETCHER, D. MILLER, Y. FUJIWARA, K. HASEGAWA, K. SANAMYAN, N. SANAMYAN, AND O. ZIMINA