Baseodiscus mexicanus, (BURGER, 1893)

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 : 530-531

BASEODISCUS MEXICANUS ( BÜRGER, 1893)

Eupolia mexicana Bürger, 1893: 236–238 , pl. 8, fig. 6, pl. 9, figs 3–6 ( Mexico); Joubin, 1905: 310 ( Mexico).

Taeniosoma mexicana: Coe, 1905: 89 , 91–92, 97, 157 ( Panama).

Baseodiscus mexicanus: Coe, 1940: 252 , 260–262, pl. 26, figs 24–26 ( Mexico, Panama); Coe, 1944: 28 ( Panama, Galapagos Islands); Friedrich, 1970: 4, 9, 11–14, table 2, fig. 3A–L ( Chile); Hochberg & Lunianski, 1998: 294 ( Mexico, Colombia, Galapagos Islands).

Material examined: None.

Sequences: KF935281 , 18S (1768 bp) ; KF935337 , 28S (2088 bp) ; KF935393 , H3 (227 bp) ; KF935449 , 16S (503 bp) ; KF935503 , COI (658 bp). Determined by Kvist et al. (2014) and deposited in GenBank as derived from isolate SK66; the voucher specimen has been deposited at the MCZ under catalogue number IZ-135321 , preserved in 95% ethanol, collected on 30 December 2001, La Paz, Faro de Puerto Balandra , Baja California Sur, Mexico, identified by G. Giribet .

External features: Body usually 20–80 cm long, but occasionally up to 2–4 m; with distinctive coloration pattern consisting of brownish green, maroon, deep red, mahogany or brownish violet background with numerous white rings encircling body at irregular intervals ( Coe, 1940).

Distribution: West coast of Mexico ( Bürger, 1893; Joubin, 1905; Coe, 1940; Hochberg & Lunianski 1998), Panama ( Coe, 1905, 1940, 1944), Colombia ( Hochberg & Lunianski, 1998), Galapagos Islands ( Coe, 1944;

Hochberg & Lunianski, 1998) and Chile ( Friedrich, 1970).

Remarks: Two partial 16S sequences deposited in GenBank, EF124863 (483 bp; La Paz, Mexico) and EF124918 (529 bp), both collected and identified by M. L. Schwartz as B. mexicanus , are identical with our sequence ( KF 935449 ).

BASEODISCUS QUINQUELINEATUS ( QUOY & GAIMARD, 1833)

( FIG. 2Q )

Borlasia quinquelineata Quoy & Gaimard, 1833: 285 , pl. 24, figs 1, 2 (New Guinea).

Taeniosoma aequale Stimpson, 1857: 162 (Amami Ōshima, Japan).

Taeniosoma septemlineatum Stimpson, 1857: 162 (Gaspar Island, Philippines).

Eupolia novemlineata Bürger, 1893: 236 , pl. 8, fig. 5 (Java, Indonesia).

Eupolia quinquelineata: Bürger, 1893: 234–236 , pl. 8, figs 2, 3 (Java and Timor, Indonesia); Bürger, 1895b: 26 ( Singapore); Punnett, 1900a: 576, pl. 40, fig. 33 ( New Caledonia; New Britain).

Eupolia septemlineata: Bürger, 1895b: 26 ( Australia) .

Eupolia melanogramma Punnett, 1900b: 113–117 ( Singapore) ; Punnett, 1900c: 826 (Torres Straits).

Eupolia trilineata Staub, 1900: 70 (595 in an alternative pagination): 85–86 (601–602), pl. 47, figs 2, 2a ( Ambon, Indonesia).

Baseodiscus quinquelineatus: Gibson, 1979: 153– 157 , figs 7C–F, 8 ( Australia); Gibson & Sundberg, 2002: 1790, fig. 3 (Rove, west of Honiara, Solomon Islands); Putchakarn, 2009: 28 (Gulf of Thailand); Venkataraman et al., 2012: 64 ( India); Kajihara, 2017: 423, fig. 16.2f (Okinawa, Japan).

Material examined: Three specimens; extracted total DNA and remaining body preserved in 99% EtOH. ICHUM 6319 , 4.5 m long, 1.2 cm wide, 24 November 2014, Irabu-jima (24°48′40″N, 125°10′54″E), collected by R. Yoshida. ICHUM 6320 , 1.2 m long, 1 cm wide, 21 May 2005, Bisezaki (26°42′35″N, 127°52′47″E), Okinawa-jima, coral reef, ~ 1 m depth, collected by H. Kajihara. ICHUM 6321 , 20 July 2013, Okinawa, collected by H. Yamasaki.

Sequences: From ICHUM 6319 : LC178602 , 18S (1789 bp) ; LC178650 , H3 (331 bp) ; LC178683 , 16S (518 bp) ; LC190955 , COI (658 bp). From ICHUM 6320 : LC178633 , 28S (1111 bp) ; LC178681 , 16S (517 bp). From ICHUM 6321 : LC178634 , 28S (1410 bp) ; LC178682 , 16S (517 bp) .

Description: Body greyish white, with five (three dorsally, two ventrally) dark-brown longitudinal stripes ( Fig. 2Q ).

Distribution: Indo-West Pacific. India ( Venkataraman et al., 2012), Torres Straits ( Punnett, 1900c), Gulf of Thailand (Putchakarn, 2009), Singapore ( Bürger, 1895b; Punnett, 1900b), Indonesia ( Bürger, 1893; Staub, 1900), Philippines ( Stimpson, 1857), Japan ( Stimpson, 1857; Kajihara, 2017; present study), New Guinea ( Quoy & Gaimard, 1833), Australia ( Bürger, 1895b; Gibson, 1979), Solomon Islands ( Gibson & Sundberg, 2002), New Caledonia ( Punnett, 1900a).

Remarks: The most common type has three stripes dorsally and two ventrally, a feature shared by the nominal taxa Borlasia quinquelineata , Eupolia trilineata and Taeniosoma aequale . However, there is almost continuous variation between the condition in the common type and that seen in other nominal taxa; for example, the dorsal stripes on both sides can be doubled (as in Taeinosoma aequale ) or tripled (as in Eupolia novemlineata ), or anteriorly tripled and posteriorly doubled (as in Taeniosoma septemlineatum ). Gibson (1979) tentatively listed these nominal taxa as potentially conspecific with Baseodiscus quinquelineatus and they are indeed likely to be so.

Gibson (1979: 154; 1995: 368)listed Eupolia lineolata ( Bürger, 1895a: 604; Bürger, 1895b: 28–29, pl. 2, figs 4, 8) from Tuamotus (originally given as ‘Paumatu-Ins.’ in Bürger, 1895a, b) and Upolu ( Samoa) as possibly synonymous with Baseodiscus quinquelineatus . However, Baseodiscus lineolatus is probably a different species, because its stripes are discontinuous and more numerous than in B. quinquelineatus . The individual shown in an in situ, underwater photo in Colin & Arneson (1995: 150, fig. 684) from Mactan Island (Cebu, Philippines) and identified as ‘ Baseodiscus delineatus ’, and another individual in Johnson & Johnson (2019a) from the Marshall Islands identified as ‘ Baseodiscus cf. delineatus ’, show stripes like those illustrated by Bürger (1895b) for B. lineolatus . Baseodiscus quinquelineatus seems to feed on terebellid polychaetes (see Potential food items below).

Figures

Figure 2. A, Eopilidion misakiense gen. et sp. nov., holotype, ICHUM 6303, lateral view, head to the right; B, Oxypolella hiebertae sp. nov., holotype, MIMB 42256; C, Cephalomastax brevis Iwata, 1957, ICHUM 6304; D, E, Valencinura jambio sp. nov., holotype, ICHUM 6305, anterior body fragment (D) and enlargement of intestinal region (E) showing yellowish proboscis (indicated by arrowheads); F, Baseodiscus takakurai Gibson, 1995, ICHUM 6306; G, Baseodiscus profundus sp. nov., holotype, MIMB 42257; H, I, Baseodiscus narusei sp. nov., holotype, ICHUM 6310, anterior end of body, dorsal (H) and ventral (I) views; J, Baseodiscus paracelensis sp. nov., holotype, MIMB 33132; K, Baseodiscus komatsui sp. nov., holotype, NMNS-Ne 1; L, Baseodiscus unicolor Stiasny-Wijnhoff, 1925; M, Baseodiscus giribeti sp. nov., holotype, MCZ IZ-135324; N, Baseodiscus cf. amboinensis (Staub, 1900); O, Baseodiscus hemprichii (Ehrenberg, 1828-1831), specimen from Okinawa, different from any voucher specimens in this study; P, Baseodiscus zebra sp. nov., holotype, RUMF-ZN-00001; Q, Baseodiscus quinquelineatus (Quoy & Gaimard, 1833), ICHUM 6319. Photographs by H. Kajihara (A, C, D, E, F, O), A.V. Chernyshev (B, G, J), T. Naruse (H, I), H. Komatsu (K), G. Giribet (L, M), D. Uyeno (P), and R.Yoshida (Q).