Baseodiscus princeps

BASEODISCUS AFF. PRINCEPS (COE, 1901 A)

(FIG. 3L, M)

Material examined: Three specimens. ICHUM 6335, extracted DNA and remaining body preserved in 99% EtOH; 21 July 2012, dredged off Miyako (between 39°38′37″N, 142°11′02″E, 197 m depth, and 39°37′58″N, 142°10′43″E, 193 m depth), Pacific coast of Honshu, Japan, collected by K. Kakui at station ‘kago- 11’ on a research cruse of the R / V Soyo-maru. ICHUM 6336, extracted DNA and remaining body preserved in 99% EtOH; 18 July 2013, dredged off Miyako (between 39°37′52″N, 142°18′13″E, 517 m depth, and 39°37′08″N, 142°17′42″E, 545 m depth), Pacific coast of Honshu, Japan, collected by K. Kakui at station ‘kago-2’ of the R / V Soyo-maru. One specimen (DNA voucher ICHUM 6337), 7 July 2011, off Kuril Island (44°36.62′N, 146°26.35′E), Ekaterina Strait, 200 m depth, collected by A. V. Chernyshev during cruise 41 of the S/ V Akademik Oparin.

Sequences: From ICHUM 6335: LC178589, 18S (1740 bp); LC178617, 28S (2101 bp); LC178660, 16S (505 bp); LC190940, COI (658 bp). From ICHUM 6336: LC178618, 28S (2097 bp); LC178661, 16S (505 bp); LC190941, COI (658 bp). From ICHUM 6337: LC178590, 18S (1797 bp); LC178619, 28S (2089 bp); LC178662, 16S (505 bp); LC190942, COI (658 bp).

Description: Background colour white, dorsally covered with broad, brown longitudinal stripe having numerous tiny perforations through which background colour can be seen; body up to 8 cm long (Fig. 3L, M).

Distribution: North-west Pacific, off Kuril Island (200 m) and off Miyako, Honshu, Japan (193–545 m) (present study). Baseodiscus princeps s.s. was originally described from three different places in Alaska, USA: Cape Fox, Yakutat and Orca (Prince William Sound) (Coe, 1901a).

Remarks: Although the PTP /bPTP analyses suggested that the three forms herein labelled B. aff. princeps, B. nipponensis and B. cf. princeps are distinct, they are genetically closely related to one another. Uncorrected p -distances for 16S between B. aff. princeps and B. nipponensis were 1.39–1.59%, between B. nipponensis and B. cf. princeps 1.19– 1.39%, and between B. aff. princeps and B. cf. princeps 0.99–1.39%; those for COI between B. aff. princeps and B. cf. princeps were 4.40–4.71% (Table 4). These values are smaller than those between other heteronemerteans that have been confirmed to be biologically distinct by cross-fertilization experiments: between Maculaura alaskensis and M. oregonensis, 4.0% for 16S and 14.3% for COI (Hiebert & Maslakova, 2015); between Kulikovia alborostrata and Kulikovia fulva, 2.8% for 16S and 14.4% for COI (Ikenaga et al., 2019).