Baseodiscus amboinensis, (STAUB, 1900)

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 : 528

publication ID	https://doi.org/ 10.1093/zoolinnean/zlac015
publication LSID	lsid:zoobank.org:pub:78C56409-FCCF-4116-8D8C-FF66B247C56C
DOI	https://doi.org/10.5281/zenodo.7043840
persistent identifier	https://treatment.plazi.org/id/038A8132-EE72-ED5F-FF27-CFD8FB61FAF5
treatment provided by	Plazi
scientific name	Baseodiscus amboinensis
status

Treatment

BASEODISCUS CF. AMBOINENSIS ( STAUB, 1900) View in CoL

( FIG. 2N View Figure 2 )

? Eupolia amboinensis Staub, 1900: 594 View in CoL , 597–599 (78, 81–83 in an alternative pagination), pl. XLVII, fig. 1, 1a, 1b, pl. XLVIII, figs 1–5 ( Ambon, Indonesia).

? Eupolia reticulata Staub, 1900: 594–595 , 599–601 (78–79, 83–85 in an alternative pagination), pl. XLVII, fig. 2, 2a, pl. XLVIII, figs 6–9 ( Ambon, Indonesia).

Baseodiscus delineatus: Chernyshev, 2011b: 22–23 View in CoL , fig. 1C (Cù Lao Thu Island, Vietnam).

Baseodiscus jonasii: Chernyshev, 2015: 548–549 View in CoL (Cù Lao Thu Island, Vietnam); Chernyshev, 2016: 289, fig. 4A (Cù Lao Thu Island, Vietnam).

Material examined: One specimen (DNA voucher ICHUM 6313 View Materials ), 18 May 2010, among dead corals, 6–9 m depth, Cù Lao Thu Island (10°32′N, 108°55′E), Vietnam, collected by A. V. Chernyshev GoogleMaps .

Sequences: From ICHUM 6313 View Materials : LC178599 View Materials , 18S (1804 bp) ; LC178629 View Materials , 28S (2086 bp) ; LC178676 View Materials , 16S (508 bp) .

Description: In life, the specimen examined ( Fig. 2N View Figure 2 ) was ‘about 1 m long, ground colour pale yellowish with numerous reddish brown longitudinal stripes situated irregularly on both dorsal and ventral surfaces; about 80–90 eyes on each side of head; transverse cephalic furrows present, each with 50–60 secondary grooves’ ( Chernyshev, 2016: 289). The mouth is small and rounded, not slit-like ( Chernyshev, 2016, fig. 4A).

Remarks: In the preserved state, Staub’s (1900) material of Eupolia amboinensis from Ambon, Indonesia, reached 30 cm in body length and 5 mm in width, with a dark background body colour having light-brown longitudinal stripes, which are interrupted, branched and reticulate. Eupolia reticulata , also from Ambon, reached up to 27cm long and 6 mm wide ( Staub, 1900), and had nearly the same external appearance as Eupolia amboinensis , and thus can be regarded as conspecific; indeed, Gibson (1979) synonymized these two nominal species under Baseodiscus delineatus , although with some reservation.

Our specimen from the South China Sea has a bright yellowish background colour, entirely overlain with longitudinal, intermittent, reddish brown stripes, which are more closely set relative to one another than in Baseodiscus delineatus ( Fig. 3C View Figure 3 ), making it difficult to tell which (bright yellow or reddish brown) is the background colour, especially in the posterior part of the body. The brown stripes appear to be narrower than those in Baseodiscus cf. curtus ( Fig. 3F View Figure 3 ). Our specimen is thus compatible with Staub’s (1900) descriptions and illustrations of Eupolia amboinensis and E. reticulata . The geographical distance of ~ 2600 km between the South China Sea and Banda Sea localities leaves room for doubt as to the identification of our material as Baseodiscus amboinensis . Barcode sequences from topotypes will be necessary to resolve this uncertainty.

Due to insufficient knowledge of the genetic diversity among species of Baseodiscus in the tropical Indo-West Pacific, our material was tentatively identified first as Baseodiscus delineatus ( Chernyshev, 2011b) and then as Baseodiscus jonasii ( Chernyshev, 2015, 2016). The uncorrected p -distance for 16S sequences between our material ( LC 178676 View Materials ) and Baseodiscus jonasii ( AY 955231 View Materials ) was 4.3%, which is greater than some values known between congeneric lineid heteronemertean species that were confirmed to be biologically different by cross-fertilization experiments, e.g. 4.0% ( Hiebert & Maslakova, 2015) between Maculaura alaskensis ( Coe, 1901a) and Maculaura oregonensis Hiebert & Maslakova, 2015 , and 2.8% ( Ikenaga et al., 2021) between Kulikovia alborostrata ( Takakura, 1898) and Kulikovia fulva ( Iwata, 1954) . Our specimen differs from B. jonasii in that the background and stripe colours are reversed between the two species: in B. jonasii , the background colour is reddish brown and the stripes are yellowish beige ( Strand et al., 2005), as in Borlasia striata Quoy & Gaimard, 1833 from Guam. The latter has a red background colour with pale reddish stripes ( Quoy & Gaimard, 1833: 286, pl. 24, figs 3, 4), and thus may be a senior synonym of B. jonasii .

V	Royal British Columbia Museum - Herbarium

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Taxonomy

Kingdom	Animalia
Phylum	Nemertea
Class	Pilidiophora
Order	Heteronemertea
Family	Valenciniidae
Genus	Baseodiscus