Baseodiscus narusei Kajihara & Abukawa & Chernyshev 2022, SP. NOV.
Creators: name: Kajihara, Hiroshi
name: Abukawa, Shushi
name: Chernyshev, Alexei V.
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Nemertea
Pilidiophora
Heteronemertea
Valenciniidae
Baseodiscus
Baseodiscus narusei

description: BASEODISCUS NARUSEI SP. NOV.
(FIGS 2H, I, 7A)
Zoobank registration: u r n: l s i d: z o o b a n k. o r g: a c t: 7 5 D 6 F E 5 2 - E A 1 1 - 4 5 5 1 - 8 E 6 F - FDAB23BDFD06.
Material examined: Holotype, ICHUM 6310, entire body and extracted total DNA preserved in 99% EtOH; 26 September 2011, among dead coral, ~ 10 m depth, SCUBA, Amitori Bay (35°09′51″N, 139°36′53″E), Iriomote Island, Japan, collected by T. Naruse.
Sequences: From the holotype: LC178598, 18S (1801 bp); LC178628, 28S (2110 bp); LC178675, 16S (504 bp); LC190951, COI (658 bp).
Etymology: The new specific name is a noun in the genitive case, after Dr Tohru Naruse (University of the Ryukyus), a Japanese decapod crustacean researcher, who found the type material.
Description: Background body colour pale greyish, densely mottled with chocolate brown pigment except laterally (Figs 2H, I, 7A). Mouth large (Fig. 2I), opening twice as long as head (i.e. from tip of head to cephalic furrow).
Distribution: So far known only from the type locality, Iriomote Island, at the southern margin of the East China Sea (present study).
Remarks: Baseodiscus narusei is most closely related to B. paracelensis; both species have a pale beige background with dark-brown mottling, but B. narusei differs from the latter in having the lateral margins of the body white. In addition, the mottling is fainter in B. narusei than in B. paracelensis, where the contrast between the mottling and the background colour is sharper. The two species differ at two of the 220 amino-acid positions translated from the 658-bp COI sequences: position 121, valine in B. narusei, isoleucine in B. paracelensis; position 140, valine in B. narusei, alanine in B. paracelensis.
At least one of the food items of Baseodiscus narusei seems to be the big blue octopus Octopus cyanea Gray, 1849 (see Potential food items below).
Sequences: From the holotype: LC178600, 18S (1773 bp); LC178649, H3 (331 bp); LC178678, 16S (504 bp); LC190952, COI (658 bp).
Etymology: The new specific name is an adjective, referring to the type locality.
Description: Body about 1 m long; background body colour pale peach yellow, mottled with amorphous, reddish brown markings, mostly dots and longitudinal lines that often merge with one another (Figs 2J, 7B). Eyes numerous. Mouth long, slit-like. Cephalic furrows well developed.
Distribution: So far known only from the type locality, the South China Sea (present study).
Remarks: With the entire body having a pale beige background mottled with brownish, B. paracelensis might previously have been confused with B. delineatus (e.g. Bürger, 1904; Gibson, 1979); however, they can easily be distinguished in that the mottles are anteroposteriorly fused to form continuous stripes, especially in the posterior part of the body, and evenly separated in B. delineatus, whereas the stripes are more often broken and irregularly separated in B. paracelensis. Baseodiscus paracelensis looks similar to B. takakurai, but differs from the latter in the colour of the mottles, which are more paler than those in B. takakurai. In Figure 1, it is the sister-species to B. narusei.
description: Published as part of 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), pp. 503-548 in Zoological Journal of the Linnean Society 196 on pages 525-526, DOI: 10.1093/zoolinnean/zlac015, http://zenodo.org/record/7037958