Baseodiscus kakuii, 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 : 537

BASEODISCUS KAKUII SP. NOV.

( FIG. 3J, K )

Zoobank registration: u r n: l s i d: z o o b a n k. o r g: a c t: 9 7 0 3 B 1 F D - 6 E 5 8 - 4 7 4 A - A 0 7 0 - 774EB904159D.

Material examined: Holotype, ICHUM 6334 , 26 May 2014, off Oki Island , Sea of Japan (between 34°04′36″N, 129°59′13″E and 34°04′32″N, 129°59′24″E), 93 m depth, collected by K. Kakui on cruise #2014-06 of the R / V Toyoshio-maru.

Sequences: From the holotype: LC178603 , 18S (1773 bp) ; LC178635 , 28S (2102 bp) ; LC178684 , 16S (506 bp) ; LC190956 , COI (658 bp) .

Etymology: The new specific name, a noun in the genitive case, refers to the collector of the holotype, Dr Keiichi Kakui (Hokkaido University), a Japanese tanaidacean systematist.

Description: Background body colour dark yellow, gradually tinged brownish mid-dorsally. Body of holotype 6.6 cm long, 2.4 mm wide (posterior end lacking) ( Fig. 3J ). Margins of dorsal brown colour evident on head; small, black eyes arranged on dorsolateral surfaces of head ( Fig. 3K ).

Distribution: Known only from the type locality, Sea of Japan (present study).

Remarks: Baseodiscus kakuii was the sister-taxon to the clade containing B. aureus , B. cf. curtus , B. urgorrii , and Clades B and C in our ML tree ( Fig. 1 ). The body coloration of B. kakuii resembles that of B. nipponensis , but the former is more yellowish and darker, and has the eyes more pronounced, than the latter.

Figures

Figure 1. Maximum-likelihood (ML) tree showing the phylogenetic relationships among 41 newly sequenced specimens of pilidiophorans (indicated with solid blue circles). Numbers near nodes are support values, ML bootstrap/Bayesian inference (BI) posterior probability. Nodes with yellow triangles are fully supported, with 100% ML bootstrap and 1.00 BI posterior probability. New species names are indicated in bold. Some nodes were polytomous in the BI tree (indicated by hyphens in place of posterior probability values).

Figure 3. A, Baseodiscus aff. marmoratus (Bürger, 1890) (voucher DNA, ICHUM 6322); B, Baseodiscus aff. maculosus (Bürger, 1895a) (voucher DNA, ICHUM 6324); C–E, Baseodiscus delineatus (Delle Chiaje, 1822-1829), ICHUM 6326; F, Baseodiscus cf. curtus (Hubrecht, 1879), ICHUM 6328; G, H, Baseodiscus urgorrii sp. nov., holotype, MCZ IZ-135319, entire body (G) and protruding proboscis (indicated by an arrowhead, H); I, Baseodiscus punnetti (Coe, 1904), specimen different from any voucher specimens in this study; J, K, Baseodiscus kakuii sp. nov., holotype, ICHUM 6334, anterior body (J) and