Dendronotus bathyvela, Martynov & Fujiwara & Tsuchida & Nakano & Sanamyan & Sanamyan & Fletcher & Korshunova, 2020

Martynov, Alexander, Fujiwara, Yoshihiro, Tsuchida, Shinji, Nakano, Rie, Sanamyan, Nadezhda, Sanamyan, Karen, Fletcher, Karin & Korshunova, Tatiana, 2020, Three new species of the genus Dendronotus from Japan and Russia (Mollusca, Nudibranchia), Zootaxa 4747 (3), pp. 495-513: 507

publication ID

https://doi.org/10.11646/zootaxa.4747.3.4

publication LSID

lsid:zoobank.org:pub:357D0749-89D1-4DE4-8BDE-A32F40C4EF38

DOI

http://doi.org/10.5281/zenodo.3704155

persistent identifier

http://treatment.plazi.org/id/28A36F6D-C221-4C34-B40A-631E3129B943

taxon LSID

lsid:zoobank.org:act:28A36F6D-C221-4C34-B40A-631E3129B943

treatment provided by

Plazi

scientific name

Dendronotus bathyvela
status

sp. nov.

Dendronotus bathyvela   sp. nov.

( Figures 4 View FIGURE 4 , 5C View FIGURE 5 )

http://zoobank.org/ 28A36F6D-C221-4C34-B40A-631E3129B943

Type material. Holotype, NSMT-Mo 94455, 45 mm long preserved, dissected, Japan, Tohoku, off Ofunato, Iwate Prefecture, 38° 53.5’ N 142° 2.8’ E, 18.10.2007, depth 303–307 m, collector K. Hasegawa, H. Komatsu GoogleMaps   . Three paratypes, NSMT-Mo 94450, 25, 26, 27 mm long (preserved), Japan, Tohoku , off Shimokita Peninsula , Aomori Prefecture, 41° 0.5’ N 141° 2.0’ E, 10.10.2006, depth 511– 510 m, collector T. Kuramochi, T. Fujita GoogleMaps   . Paratype, NSMT- Mo 94452, 35 mm long (preserved), Japan, Tohoku, off Kinkazan , Miyagi Prefecture, 38° 23.2’ N 141° 58.2’ E, 04.11.2006, depth 305–309 m, collector H. Komatsu. GoogleMaps   Paratype, NSMT-Mo 93078, 35 mm long (preserved), Japan, Tohoku, off Kesennuma , Miyagi Prefecture, 38° 4.6’ N 141° 55.3’ E, 19.11.2005, depth 249 m, collector T. Fujita, H. Saito GoogleMaps   . Paratype, NSMT-Mo 93080, 21 mm long (preserved), Japan, Tohoku, off Kesennuma , Miyagi Prefecture, 38° 4.2’ N 141° 58.9’ E, 19.11.2005, depth 306–309 m, collector T. Fujita, H. Saito GoogleMaps   . Paratype, NSMT-Mo 93061, 14 mm long (preserved), Japan, Tohoku, off Kinkazan , Miyagi Prefecture, 38° 2.3’ N 142° 2.1’ E, 17.11.2005, depth 382– 376 m, collector T. Fujita, H. Saito GoogleMaps   .

Type locality. Japan, off the Pacific coast of Northern Honshu   .

Etymology. From Ancient Greek βάθος (deep sea) + velum (veil) in reference to the deepest record so far known of this wide-bodied Dendronotus   species with a broad oral veil.

Diagnosis. Body broad, 6–7 pairs dorsolateral appendages, colour dull reddish-brownish with numerous white spots, central tooth with well-defined denticles and furrows, vas deferens moderate in length, penis long, very thin.

Description. Body broad, up to 45 mm in length ( Fig. 4 View FIGURE 4 A–D), 10–15 long branched appendages of oral veil, 5 appendages of rhinophoral stalks, 15–25 rhinophoral lamellae, branched rhinophoral lateral papilla absent, 6–7 pairs dorsolateral appendages (including smallest posterior ones), ca. 50–70 lip papillae. Dorsolateral appendages with moderate primary stalk, moderately branched secondary branches, and elongated tertiary branches ( Fig. 4 View FIGURE 4 A–D). Reproductive and anal openings placed laterally on right side. General colour dull reddish-brownish with numerous distinct opaque white dots on notum, tips of lateral appendages, oral appendages ( Fig. 4 D View FIGURE 4 ).

The jaws are ovoid with strong dorsal processes, denticles present ( Fig. 4 View FIGURE 4 E–F). Masticatory processes apparently bear ca 60 denticles. Radula formula is 36 × 1–13.1.13–1 (paratype 21 mm), 41 × 1–12.1.12–1 (paratype 27 mm), 37 × 1–13.1.13–1 (paratype 35 mm), 36 × 1–14.1.14–1 (holotype 45 mm). Central tooth with broad, relatively low cusp, strongly denticulated and bearing up to over 30–35 distinct to small denticles ( Fig. 4G View FIGURE 4 ). Lateral teeth are long, slightly curved, commonly completely smooth or bearing few (up to 2) weak denticles ( Fig. 4H View FIGURE 4 ).

Reproductive system triaulic ( Fig. 5C View FIGURE 5 ), ampulla folded several times ( Fig. 5C View FIGURE 5 , am), prostate consisting of 21–25 alveolar glands ( Fig. 5C View FIGURE 5 , pr), vas deferens long ( Fig. 5C View FIGURE 5 , vd) expanding to elongate penial sheath ( Fig. 5C View FIGURE 5 , psh), penis very long, thin ( Fig. 5C, p View FIGURE 5 ), vagina very long and considerably twisted ( Fig. 5C View FIGURE 5 , vg), bursa copulatrix is large, rounded, and elongated ( Fig. 5C View FIGURE 5 , bc) with small seminal receptaculum placed distally ( Fig. 5C View FIGURE 5 , rs).

Biology. Inhabits sand and muddy substrates with stones.

Distribution. Presently known only off the Pacific coast of Northern Honshu ( Japan), at depths of 249– 510 m.

Remarks. According to the morphological data Dendronotus bathyvela   sp. nov. clearly belongs to the group of wide-bodied Dendronotus   species, which includes only a few species, i.e. D. patricki   , D. robustus   and D. velifer   . Because all available D. bathyvela   sp. nov. were formalin-fixed, this prevented us from including this species in the molecular phylogenetic analysis. However, the present morphological data are enough to distinguish D. bathyvela   sp. nov. from all other wide-bodied species of the genus Dendronotus   . The abyssal NE Pacific species, D. patricki   , readily differs from the bathyal NW Pacific D. bathyvela   sp. nov. by its uniform pinkish colouration (white pig- ment presents only on apices of dorsolateral and velar appendages, but not on the body) and details of the radula ( Stout et al., 2011). Particularly, in D. patricki   the number of lateral teeth is up to eight, whereas in D. bathyvela   sp. nov. —up to 14. The number of lateral denticles on the central teeth is about 20 in D. patricki   , whereas in D. bathyvela   sp. nov. there are over 30 denticles. Previously, D. robustus   had been recorded from the Sea of Japan and the Pacific side of Honshu ( Roginskaya 1997; Hasegawa 2009). However, the true D. robustus   from the shallow waters of the North Atlantic (see Lundin et al. 2017) considerably differs from the North Pacific material in the details of colouration and the radula. For a long time, D. velifer   from Northern Europe and the Arctic was also confused with D. robustus   , however recently it was shown that this is a distinct species, according to both morphological and molecular data ( Lundin et al. 2017). The following differences between D. velifer   and D. bathyvela   sp. nov. are: 1) Appendages of the oral veil in living specimens of D. velifer   are distinctly shorter than in living D. bathyvela   sp. nov. ( Fig. 4 View FIGURE 4 A–D); 2) Large specimens of D. velifer   commonly bear not more than four main dorsolateral appendages (an exceptionally large specimen was reported as having up to five main appendages plus a sixth smaller one), whereas even moderately sized D. bathyvela   sp. nov. possess up to six main dorsolateral appendages (plus a seventh smaller one); 3) Colouration of living specimens of D. velifer   is bright reddish, whereas D. bathyvela   sp. nov. is dull reddish-brownish ( Fig. 4D View FIGURE 4 ); 4) Number of denticles on the central teeth of D. velifer   is commonly less than 30, whereas in D. bathyvela   sp. nov. it reaches over 30; 5) Number of radular rows in D. velifer   is up to 36, whereas in D. bathyvela   sp. nov. the number of rows is up to 41 and more. It is remarkable that the North Atlantic shallowwater species D. robustus   has up to seven dorsolateral appendages, like the NW Pacific shelf to bathyal new species D. bathyvela   sp. nov., but not like the true predominantly Arctic shelf species D. velifer   , which commonly has only four dorsolateral appendages. This feature readily distinguishes D. bathyvela   sp. nov. from D. velifer   . At the same time, D. bathyvela   sp. nov. is well-distinguished from D. robustus   by the shape of the central radula and external colouration. Bathymetrically D. velifer   is known from relatively shallow waters with a range commonly ca. 15–230 m, whereas D. bathyvela   sp. nov. inhabits the low part of the continental shelf (not shallower than 249 m) to upper bathyal (510 m) depths. True North Atlantic D. robustus   is in turn exclusively a shallow water species and was not recorded deeper than 20–30 m (see Lundin et al. 2017). This set of several complex morphological and ecological features allow us to distinguish D. bathyvela   sp. nov. from D. velifer   . Recently a deep-sea (but not wide-bodied) species, D. claguei, was described ( Valdés et al. 2018) off the NE Pacific coast. D. claguei fundamentally differs from D. bathyvela   sp. nov. by its uniform translucent white colour, elongate body shape, radular details, and in addition D. claguei inhabits upper abyssal depths (2369 m) and not shelf to upper bathyal depths (249–510 m) as D. bathyvela   sp. nov. does. In addition, the NE Pacific shallow-water species D. albopunctatus Robilliard, 1972 is somewhat similar to the wide-bodied species group of the genus Dendronotus   , but has fewer, and longer, oral veil appendages, lacks lip papilla and considerably differs by the presence of distinct denticulation on the lateral teeth of the radula ( Robilliard, 1972).

T

Tavera, Department of Geology and Geophysics