Baseodiscus komatsui, Kajihara & Abukawa & Chernyshev, 2022

Kajihara, Hiroshi, Abukawa, Shushi & Chernyshev, Alexei V., 2022, Exploring the basal topology of the heteronemertean tree of life: establishment of a new family, along with turbotaxonomy of Valenciniidae (Nemertea: Pilidiophora: Heteronemertea), Zoological Journal of the Linnean Society 196, pp. 503-548 : 526-527

BASEODISCUS KOMATSUI SP. NOV.

( FIGS 2K , 6F )

Zoobank registration: u r n: l s i d: z o o b a n k. org:act: 28FE54EB-D2A3-4D1F-9A60-302696A12338.

Material examined: Two specimens; detailed depth information lacking for both, but probably<20 m depth. Holotype, NMNS-Ne 1 (DNA voucher ICHUM 6342 ), 27 June 2014, subtidal, SCUBA diving, Nishijima-Oiwa (27°07′06″N, 142°10′19″E), Ogasawara Islands , Japan, collected by H. Komatsu. Paratype, ICHUM 6312 , 27 May 2001, subtidal, SCUBA diving, among coral rubble, Kakeroma-jima (c. 28°7′29″N, 129°14′41″E), Kagoshima, Japan, collected by H. Kajihara.

Sequences: From the holotype: LC178597 , 18S (1775 bp) ; LC178627 , 28S (2107 bp) ; LC178648 , H3 (331 bp) ; LC178673 , 16S (504 bp). From the paratype: LC178596 , 18S (1798 bp) ; LC178626 , 28S (2123 bp) ; LC178672 , 16S (479 bp) .

Etymology: The new specific name is a noun in the genitive case, after Dr Hironori Komatsu (National Museum of Nature and Science, Japan), a Japanese carcinologist, who collected the holotype specimen.

Description: Background body colour beige, uniformly mottled with brown to dark-olive dots and lines on dorsal, ventral and lateral surfaces of body ( Figs 2K , 6F ). Eyes and cephalic furrows (with secondary furrows) present, as in congeners. In life, holotype 120 cm long, 8 mm wide; paratype, 16 cm long, 2.5 mm wide.

Distribution: So far known from the Ogasawara Islands (type locality) and the island of Kakeromajima in Japanese waters, but probably more widely distributed in warm waters in the western Pacific.

Remarks: The mottling pattern in Baseodiscus komatsui resembles that in B. takakurai , but the two species differ in body colour: the mottling is much paler in the former than in the latter, where it is dark brown or black; the background colour is light beige in B. komatsui , yellowish in B. takakurai . The mottling tends to be blurred in the posterior part of the body in B. komatsui . These two species differ at six of the 220 amino-acid positions translated from the 658-bp COI sequences: positions 118 and 122, alanine in B. komatsui , serine in B. takakurai ; 126, glycine in B. komatsui , alanine in B. takakurai ; 154, isoleucine in B. komatsui , valine in B. takakurai ; 159, arginine in B. komatsui , leucine in B. takakurai ; 190, glycine in B. komatsui , alanine in B. takakurai .

Figures

Figure 2. A, Eopilidion misakiense gen. et sp. nov., holotype, ICHUM 6303, lateral view, head to the right; B, Oxypolella hiebertae sp. nov., holotype, MIMB 42256; C, Cephalomastax brevis Iwata, 1957, ICHUM 6304; D, E, Valencinura jambio sp. nov., holotype, ICHUM 6305, anterior body fragment (D) and enlargement of intestinal region (E) showing yellowish proboscis (indicated by arrowheads); F, Baseodiscus takakurai Gibson, 1995, ICHUM 6306; G, Baseodiscus profundus sp. nov., holotype, MIMB 42257; H, I, Baseodiscus narusei sp. nov., holotype, ICHUM 6310, anterior end of body, dorsal (H) and ventral (I) views; J, Baseodiscus paracelensis sp. nov., holotype, MIMB 33132; K, Baseodiscus komatsui sp. nov., holotype, NMNS-Ne 1; L, Baseodiscus unicolor Stiasny-Wijnhoff, 1925; M, Baseodiscus giribeti sp. nov., holotype, MCZ IZ-135324; N, Baseodiscus cf. amboinensis (Staub, 1900); O, Baseodiscus hemprichii (Ehrenberg, 1828-1831), specimen from Okinawa, different from any voucher specimens in this study; P, Baseodiscus zebra sp. nov., holotype, RUMF-ZN-00001; Q, Baseodiscus quinquelineatus (Quoy & Gaimard, 1833), ICHUM 6319. Photographs by H. Kajihara (A, C, D, E, F, O), A.V. Chernyshev (B, G, J), T. Naruse (H, I), H. Komatsu (K), G. Giribet (L, M), D. Uyeno (P), and R.Yoshida (Q).

Figure 6. A–E, Baseodiscus takakurai Gibson, 1995, ICHUM 6308, A, anterior end of body, ventral view; B, middle body region, showing appearance of body markings in differently contracted states; C, juvenile, showing dorsal mottling; D, juvenile, with head viewed ventrolaterally, showing two ocelli; E, transverse section of proboscis; F, Baseodiscus komatsui sp. nov., holotype, NSNM NMNS-Ne 1, entire body. Photos by H. Kajihara (A–E) and H. Komatsu (F).