Dendronotus lacteus ( Thompson, 1840 )

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 : 124-125

Dendronotus lacteus ( Thompson, 1840)

Fig. 7

Tritonia lactea Thompson, 1840: 88–89 , Pl. 2, Fig. 3 .

Dendronotus lacteus Eliot, 1910: 161 ; Nordsieck, 1972: 68; Pruvot-Fol, 1954: 356; Thollesson, 1998: 191–193, Figs 1–3 ; Evertsen and Bakken, 2005: 18; Korshunovaet al., 2017: 2–7, Figs 1 , 2.

not Becher, 1886: 14.

not Eliot, 1910:112 (= D. dalli ).

= D. frondosus auct. non Ascanius, 1774.

Extended diagnosis. Body relatively narrow. Four to eight pairs of branched dorsolateral appendages which in adults commonly show specific “curly” patternthoughotherspecimens with more “typical” for genus Dendronotus elongated appendages may occur. Four to ten oral veil appendages. Four to six appendages (inetrnal middle and posterior ones longest) of rhinophoral stalks. Lateral papilla of rhinophoral sheaths present. Rhinophores with 10–14 lamellae. At least more than 15 lip papillae.Basalcolourfromuniformlydarkredto uniform white, often with small brownish dots. Redddish and brownish specimens may have white stripes between cerata, white specimens milky, non-transparent in appearance. Dorsal processes of jaws inclined posteriorly at approximately 55–60° to the longitudinal axis of the jaw body and 0.52 of its length. Masticatory processes possibly bear denticles and ridge-like structures. Radula with up to 43 rows of teeth. Central tooth with up to 40–50 small denticles (commonly smaller), often with peculiar ribs, never completely smooth. Up to 16 lateral teeth with up to five denticles. Ampulla moderately narrow with several windings or folded loops. Bursa copulatrix large, rounded to oval. Seminal receptaculum small placed distally at considerable distance from the vaginal opening. Prostate discoidwith a range from 12 to morethan 30 alveolar glands. The vas deferens is relatively long in length, penis relatively long, bent. Body length up to 150 mm.

Distribution. North Atlantic and Arctic (eastern limit at least Laptev Sea, Russia).

Bathymetry. From circa 5 to 427 m depth; commonat shallow, subtidal depthsat around 10– 20 m.

Remarks. Dendronotus lacteus together with D. frondosus and D. europaeus form a species complex that is difficult to distinguish based on external characteristics, but in which it is still possible to find fine-scale morphological differences. In contrast, the radulae of these three species demonstrate distinctly different patterns ( Korshunova et al., 2017b).

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 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