Dendronotus robustus Verrill 1870

Dendronotus robustus Verrill, 1870

Fig. 7

Dendronotus robustus Verrill, 1870: 405; Lundin et al., 2017: 303, 306, 309–315, Figs 3, 4.

Non auct., not Ekimova et al. (2015) (mix-up with D. velifer G.O. Sars, 1878).

Extended diagnosis. Body wide. Six to seven pairs of branched dorsolateral appendages. 10 to 15 appendages of oral veil. Four to five appendages of rhinophoral stalks. Lateral papilla of rhinophoral sheaths absent. Rhinophores with 7–14 lamellae. More than 20 lip papillae. Basal colour light grayish to yellowish with scattered opaque white and yellow spots. Dorsal processes of jaws inclined posteriorly at approximately 47° to the longitudinal axis of the jaw body and 0.55 of its length. Masticatory processes apparently bear denticles (may possess ridgelike structures). Radula with upto 31 rows of teeth. Central tooth with high cusp and up to 20 small distinct denticles without furrows. Up to nine lateral teeth with up to seven denticles. Ampulla moderately narrow, with approximately three to four irregular loops. Bursa copulatrix moderate in size, rounded to pear-shaped,withsmallseminalreceptaculum placed distally near the vaginal opening. Prostate discoid with about 10 alveolar glands. The vas deferens is moderate in length, penis massive, broad, slightly curved. Bodylength of verified specimens up to 50 mm.

Distribution. North Atlantic (both western and eastern, Canada, Norway, Russia and USA), very shallow waters only, in the Arctic, the

range does not extend further eastward than the Barents Sea.

Bathymetry. Intertidal to less than 20 m deep.

Remarks. T.A. Korshunova’s and A.V. Martynov’s pre-2015 analysis has showed that there are at least two species in the “ D. robustus complex”, namely D. robustus Verrill, 1870 and D. velifer G.O. Sars, 1878. However, this analysis was unfortunately not included in the final version of the publication by I.A. Ekimova (Ekimova et al., 2015). This detailed morphological and molecular analysis has shown that D. robustus and D. velifer are well differentiated morphologically, bathymetrically and according to the molecular analysis (Lundin et al., 2017). In the previous literature these two species have been mixed.