BASEODISCUS TAKAKURAI GIBSON, 1995

(FIGS 2F, 6A–E)

Eupolia sp.: Takakura, 1898: 185, fig. 8 (Misaki, Japan).

Baseodiscus takakurai Gibson, 1995: 304, 367; Kajihara, 2017: 423, fig. 16.2.

Material examined: ICHUM 6266, transverse sections, 5 µm thick, Mallory, 43 slides, along with unsectioned body fragment in 99% EtOH; March 2012, under stone, subtidal, 10 m depth , SCUBA diving, mouth of Koajiro Bay (35°09′51″N, 139°36′53″E), K a n a g awa, Ja p a n, c o l l e c t e d b y H. K o h t s u k a . ICHUM 6306, body fragment in 99% EtOH, 4 June 2012, among laminarian holdfasts, rocky intertidal, Oshoro Bay (43°12′43″N, 140°51′13″E), Hokkaido, Japan, collected by H. Kajihara. ICHUM 6307, body fragment in 99% EtOH, collection data same as for ICHUM 6266 . ICHUM 6309, body fragment in 99% EtOH, juvenile, 18 April 2014, among roots of the seagrass Phyllospadix iwatensis Makino, Oshoro Bay, Hokkaido, Japan, collected by H. Kajihara. ICHUM 6308, anterior body fragment (~70 cm long) in 99% EtOH, 24 August 2016, among sunken scallop shells used for sea cucumber mariculture, 5 m depth, 300 m offshore, Date (42°27′30″N, 140°52′03″E), Hokkaido, Japan, collected by H. Kajihara.

Sequences: From ICHUM 6266: LC178612, 28S (2120 bp); LC178645, H3 (331 bp); LC178654, 16S (507 bp). From ICHUM 6306: LC178583, 18S (1795 bp); LC178610, 28S (2094 bp); LC178652, 16S (506 bp). From ICHUM 6307: LC178611, 28S (2121 bp); LC178644, H3 (331 bp); LC178653, 16S (507 bp); LC190937, COI (658 bp). From ICHUM 6309: LC178584, 18S (1793 bp); LC178613, 28S (2120 bp); LC178646, H3 (331 bp); LC178655 16S (507 bp); LC190938, COI (658 bp) .

Description: Background body colour wheat to light orange, mottled with black to dark brown patches of varying size and shape (Figs 2F, 6A, B); body markings uniformly distributed both dorsally and ventrally in large specimens, but only dorsally in juveniles (Fig. 6C, D). Head demarcated from body with transverse cephalic furrow; secondary furrows present. Mouth mid-ventral, behind cephalic furrow (Fig. 6A). Eyes numerous, arranged along cephalic margin on each side, also on dorsal surface of head just anterior to cephalic furrow (sparse near midline). No caudal cirrus. Proboscis pore terminal. Rhynchocoel wall consisting of inner longitudinal and outer circular muscle layers. Proboscis wall composed of glandular epithelium, neural plexus, outer longitudinal muscle layer, and inner circular muscle layer (Fig. 6E).

Distribution: So far confirmed only from eastern Japan: Misaki, Honshu (type locality; Takakura, 1898; present study); Date, Hokkaido (present study); and Oshoro, Hokkaido (present study).

Remarks: Takakura (1898) recorded an unidentified form as Eupolia sp., stating that it resembled Eupolia antillensis Bürger, 1895a . Gibson (1995) mistakenly thought that Takakura (1898) had established a new taxon with the specific name antillensis, and introduced the new name Baseodiscus takakurai for Takakura’s (1898) Eupolia sp.