Baseodiscus marmoratus
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 marmoratus

description: BASEODISCUS AFF. MARMORATUS (BÜRGER, 1890)
(FIGS 3A, 7C)
? Eupolia marmorata Bürger, 1890: 24, pl. I, fig. 11, pl. II, fig. 26, pl. V, fig. 73.
? Baseodiscus delineatus: Gibson, 1979: 139 (in part).
Material examined: Two specimens, both collected by A. V. Chernyshev; one specimen (DNA voucher ICHUM 6322) collected 19 May 2010, among dead corals, 6–8 m depth, Cù Lao Thu Island (10°31′N, 108°55′E), Vietnam; the other (DNA voucher ICHUM 6323) collected 26 May 2010, among dead corals, 5–10 m depth, Cù Lao Chàm Island (15°53′N, 108°31′E), Vietnam.
Sequences: From ICHUM 6322: LC178585, 18S (1812 bp); LC178614, 28S (1114 bp); LC178656, 16S (516bp). From ICHUM 6323: LC178586, 18S (1808 bp); LC178657, 16S (516 bp).
Description: Body about 20 cm long, pale yellowish, with numerous, brown, short, broken longitudinal stripes covering entire dorsal side (Fig. 3A); ventral surface of head without brown pigmentation; sparse brown patches present ventrally behind mouth (Fig. 7C). Head with approximately 60 eyes in each half.
Distribution: Baseodiscus marmoratus s.s. (see below) is known only from Ambon, Indonesia (Bürger, 1890). Our material from Vietnam is of uncertain affinity to that species.
Remarks: We identified our specimens from Vietnam with uncertainty as Baseodiscus aff. marmoratus. Bürger (1890) noted that his material for Eupolia marmorata from Ambon ranged from 3–4 mm wide × 6–8 cm long to 8 mm wide × 20 cm long; the mouth is small and pore-like; the background body colour is whitish; dorsally there are fine, anastomosing, dark-brown longitudinal lines of longitudinal striation, forming a dense network; ventrally, the edges of the striae are farther apart, leaving the background body colour more visible. Our specimens from Vietnam have the stripes more discontinuous and sparser than those in E. marmorata and thus may represent a different species. Reliable identification will require barcode sequences from topotypes.
Bürger (1904: 82) synonymized Eupolia marmorata with B. curtus, and Gibson (1995: 368) later synonymized it with Baseodiscus delineatus. Here we combine the specific name marmorata with Baseodiscus, as B. marmoratus. Our material agrees with Bürger’s (1890) description and illustration for E. marmorata in that the background body colour is pale yellowish, covered with brownish, broken stripes. This colour pattern itself is similar to that of B. delineatus, but B. marmoratus differs from B. delineatus in having the stripes darker and more closely set to one another, especially in the posterior part of the body. Baseodiscus marmoratus cannot be confused with B. curtus because the ventral surface of the body in the latter is devoid of stripes or markings. In terms of uncorrected p -distance for 524-bp 16S sequences in our dataset, B. aff. marmoratus differed by 14.9–15.2% from B. cf. curtus and by 11.9% from B. delineatus. Baseodiscus aff. marmoratus seems to feed on terebellid polychaetes (see Potential food items below).
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 page 531, DOI: 10.1093/zoolinnean/zlac015, http://zenodo.org/record/7037958