BASEODISCUS AFF. MACULOSUS (BÜRGER, 1895 A)

(FIG. 3B)

Baseodiscus cf. delineatus: Chernyshev, 2016: 290 (in part) (Cù Lao Re Island, Vietnam).

? Eupolia maculosa Bürger, 1895a: 604; Bürger, 1895b: 28, pl. 2, fig. 2 (Pohnpei, Caroline Islands, Micronesia).

? Baseodiscus maculosus: Bürger, 1904: 84; Gibson, 1995: 304, 368.

? Baseodiscus delineatus var. curtus: Coe, 1940: 261 (in part).

Material examined: One specimen (DNA voucher ICHUM 6324), 23 May 2007, among dead corals, 2–4 m depth, Cù Lao Re Island (15°23′N, 109°05′E), Vietnam, collected by A. V. Chernyshev .

Sequences: From ICHUM 6324: LC178674, 16S (482 bp); LC190950, COI (658 bp) .

Description: Body 3–4 cm long. Background body colour pale yellow, mottled over entirety with numerous minute brown dots (Fig. 3B); dots sparser ventrally. Head with numerous eyes and two transverse cephalic furrows, each with secondary grooves.

Distribution: Baseodiscus maculosus s.s. is known only from the original description from Pohnpei (formerly, Ponape), Caroline Islands, Micronesia (Bürger, 1895b); our specimen identified as Baseodiscus aff. maculosus was from Vietnam.

Remarks: Our specimen was collected from Cù Lao Re Island, Vietnam, 5400 km distant from the type locality. We tentatively identify it as B. aff. maculosus on the basis of the similarity in body markings, consisting of minute, dark-coloured dots spread all over the pale-coloured body. However, the dots in the Vietnam specimen are denser than indicated in the original illustration (Bürger, 1895b, pl. 2, fig. 2) and its body (3–4 cm) was much shorter than Bürger (1895a, b) indicated for the type specimen (c. 50 cm long, 6 mm wide). The specimen from Vietnam may thus represent a different species. Johnson & Johnson (2019b) photographed an individual from the Marshal Islands (labelled ‘ Emplectonema ? sp. 1’) that was more than 1 m long, with sparser spots and appears much more similar to B. maculosus . Coe (1940) wrote that part of the material he identified as B. delineatus var. curtus differed from B. delineatus in having ‘markings composed of small red or brown dots’, suggesting that the former taxon might include B. maculosus . Baseodiscus aff. maculosus seems to feed on terebellid polychaetes (see Potential food items below).