Careproctus trachysoma Gilbert & Burke 1912

Careproctus trachysoma Gilbert & Burke 1912

English common name: Rough Snailfish Japanese common name: Zara-bikunin

Figures 1 B–C, 5B, 6; Tables 1–3

Careproctus trachysoma Gilbert & Burke 1912:364, pl. 44, fig. 1. Type locality: Sea of Japan, 43°N, 140.1722°E.— Burke 1930:137, fig. 60 (description, key).— Soldatov & Lindberg 1930:27 (Sea of Okhotsk, key, = C. rastrinus ?).— Chapman & DeLacy 1934:3 (comparisons).— Taranetz 1937:137 (Sea of Japan, in key).— Okada & Matsubara 1938:346 (Niigata and west coast of Hokkaido, Japan, Gulf of Tartary).— Schmidt 1950:204 (brief description, Russia).— Honma 1952:224 (Sea of Japan).— Böhlke 1953:136 (type catalog).— Matsubara 1955:1193 (Sea of Japan, in key).— Kato, 1956:329 (Sea of Japan, list).— Honma 1963:224 (Niigata, Japan, list).— Ueno 1971:97 (Sea of Japan, Sakhalin).— Quast & Hall 1972:29 (Alaska).—Honma & Kitami 1978:62 (Niigata, Japan, list).—Kido 1984:339, pl. 305-C (brief description, Sea of Japan, Tartary Strait, Sea of Okhotsk, in part).— Lindberg & Krasyukova 1987:450 (Sea of Japan, west coast of Hokkaido, Japan, Gulf of Tartary, = C. rastrinus ?).— Kido 1988:220, fig. 50 (description, phylogenetics, in part?).— Nambu & Kido 1990:111 (Sea of Japan).— Pitruk 1990:38 (list, Seas of Japan and Okhotsk, in part?).— Tsuda 1990:513 (Sea of Japan, Hokkaido, Sakhalin, Sea of Okhotsk, in part).— Nambu et al. 1992:74 (Yamato Bank, Sea of Japan).—Nakabo 1993:586 (Sea of Japan, Tartary Strait, Sea of Okhotsk, in key, in part).— Amaoka et al. 1995:211 (Sea of Japan, Sea of Okhotsk, in part).— Kido 1997:244 (Sea of Japan and Sea of Okhotsk, in part).—Nakabo 2000:672 (Sea of Japan, Hokkaido, Sakhalin, Sea of Okhotsk, in part), Nakabo 2002:672 (Sea of Japan, Hokkaido, Sakhalin, Sea of Okhotsk, in part).— Maeda & Tsutsui 2003:495 (Sea of Japan and Sea of Okhotsk coasts of Hokkaido, in part, = C. rastrinus ?).— Chernova et al. 2004:17 (checklist, in part?).— Okiyama 2004:413 (Sea of Japan).— Chernova 2005b:S7 (comparisons).— Kai et al. 2011a:144 (genetics, morphology, phylogenetics, as “SOJ1” and “SOJ2”).— Kai et al. 2011b:366 (genetics, as “SOJ1” and “SOJ2”).— Shinohara et al. 2011:47 (Sea of Japan).— Shinohara et al. 2014:257 (Sea of Japan).

Holotype. USNM 73333, 227 mm, Japan, Sea of Japan, off Iwanai, off Otaru, Hokkaido, Benkei Mizaki Light, S 3°E, 17 km, 43°N, 140.1722°E, Albatross station 4982, depth 783 m, 19 September 1906.

Paratypes. SU 22376, 2 (120.8–201.8 mm), Japan, between Hakodate and Otaru, Hokkaido, via Tsugaru Strait, Benkei Mizaki Light, S 2°, 43.0264°N, 140.1778°E, Albatross station 4983, 782.7 m, 19 September 1906.

Additional material examined. A total of 39 specimens, not including the types above, 101.6–264.8 mm SL. See “Non-type material examined below.”

Diagnosis. Careproctus trachysoma is distinguished from all other species of Careproctus by the combination of cyt b and 16S rRNA sequences (“SOJ1” and “SOJ2” of Kai et al. 2011; Table 1), an anteriorly robust body more or less covered by cactus-like prickles, presence of the postorbital pore, moderate-sized pelvic disc, lower pectoralfin lobe longer than upper lobe, speckled peritoneum, dark stomach, and, unlike other members of the C. rastrinus species complex, a dark color morphotype. It is most similar to C. rastrinus of the western Pacific, from which it can also be distinguished by its peritoneum and stomach color (pale and speckled gray in C. rastrinus), and a less deep and shorter head and anterior body. It is also similar to C. scottae, from which it can be distinguished by its higher counts of caudal vertebrae (51–56 in C. trachysoma vs. 48–52 in C. scottae) and anal-fin rays (51–57 vs. 47–53), and peritoneum and stomach color (both pale in C. scottae), smaller pelvic disc (11.1–18.1 vs. 13.9–26.5 % HL), and shorter nasal tube (1.3–4.3 vs. 2.1–6.4 % HL), and to C. phasma from which it can be distinguished by the postorbital pore (present in C. trachysoma vs. absent in C. phasma), smaller pelvic disc (11.2–18.1 vs. 20.1– 35.9 % HL), shorter nasal tube (1.3–4.3 vs. 2.9–5.7 % HL), peritoneum and stomach color (pale in C. phasma), higher counts of dorsal-fin rays (57–62 vs. 50–56), higher counts of anal-fin rays (51–57 vs. 43–49), and higher counts of caudal vertebrae (51–56 vs. 44–50). It is further distinguished from C. spectrum by its higher counts of dorsal-fin rays (57–62 vs. 52–54 in C. spectrum), smaller orbit (16.7–28.3 vs. 33.9–34.4 % HL), and smaller pelvic disc (11.2–18.1 vs. 22.5–23.1 % HL).

Description. Body heavy and deep anteriorly, tapering strongly posteriorly, moderately compressed; depth at pectoral-fin base 87.3–133.2 % (125.5) % HL. Head short, 19.3–26.3 (23.1) % SL, robust, dorsal profile rounded from nape to snout. Snout blunt, slightly projecting anterior to lower jaw. Mouth terminal, small, horizontal; upper jaw 35.5–51.5 (42.3) % HL, maxilla extending to anterior rim of orbit or mid-orbit, oral cleft extending to anterior rim of orbit; mandible 42.1–55.6 % HL. Premaxillary tooth plates matching mandibular tooth plates. Premaxillary and mandibular teeth simple with weak shoulders in 21–47 oblique rows of 7–14 teeth forming narrow bands. Diastema absent at symphysis of upper and lower jaws. Orbit 16.7–28.3 (23.5) % HL, dorsal margin well below dorsal contour of head, suborbital depth to upper jaw 11.3–15.3 % HL, to lower jaw 26.6–38.0 % HL; pupil round. Interorbital space broad, fleshy distance 38.5–61.6 (49.2) % HL, bony distance 22.9–33.0 % HL, strongly convex. Snout much longer than orbit, 109.2–223.7 (143.3) % OL, 30.9–43.8 (33.6) % HL. Nostril single, with welldeveloped tube at level with lower rim of orbit; nostril tube length 12.3–24.2 % OL.

Pores of cephalic lateralis system of moderate size, pore pattern 2-6-7-2, chin pores paired. Interorbital pore absent.

Gill opening small, 21.1–43.9 (28.8) % HL, upper margin at level of mid-orbit or dorsal rim of orbit, extending ventrally to just above the upper pectoral-fin ray to pectoral-fin ray 1–3 (ray 3). Opercular flap rounded to slightly angular (rounded). Gill rakers 8–11 (Tables 2–3), short, blunt.

Dorsal-fin rays 57–62 (61; Tables 2–3), anterior dorsal lobe absent, anterior rays buried in tissue, tips of more posterior rays not exserted. Anteriormost dorsal-fin pterygiophore often rayless, inserted between neural spines 2 and 3 or 3 and 4 (between 3 and 4). Predorsal length 21.9–30.4 (25.0) % SL. Anal-fin rays 51–57 (53; Table 2–3), one to four anal-fin pterygiophores anterior to first haemal spine (two), each bearing a single ray, tips of rays not exserted. Anal-fin origin below vertebrae 13–14 (caudal vertebrae 2–3), preanal length 31.4–44.4 (32.1) % SL.

Pectoral fin deeply notched, with 31–37 (31) rays (Table 2–3). Upper lobe 55.8–89.9 (73.4) % HL, with 21–31 (24) rays extending beyond anus to or near anal-fin origin, shorter than lower lobe, dorsalmost rays lengthening to rays 4–5, more ventral rays gradually shortening to shortest ray of notch. Lower lobe elongate, 77.7–132.5 (101.3) % HL, with 7–10 rays (8), extending beyond anus to or near anal-fin origin; dorsal rays gradually lengthening to elongate rays 4–5, ventral rays gradually shortening to ventralmost ray near pectoral symphysis. Tips of rays of dorsal lobe enclosed by membrane dorsally, up to 40% free of membrane in notch; rays of lower lobe more strongly exserted, 50–60% free. Notch strong, rays in notch slightly more widely spaced than rays of lobes, more widely spaced ventrally. Uppermost pectoral-fin ray level with region between ventral rim of orbit and oral cleft. Insertion of lowermost pectoral-fin ray below mid-orbit. Proximal pectoral radials four (3+1), robust: radials 1–2 notched and hour-glass shaped, radial 3 round, with deep dorsal notch, radial 4 a rounded square (Fig. 5 B). Interradial fenestrae three, extending between scapula and proximal radials 1–3: fenestrae between the scapula and radials 1 and 2 elliptical, fenestra between radials 2 and 3 narrow and dorsoventrally elongate. Scapula broadly T-shaped with robust distally broadened helve; coracoid with broad triangular head and broad helve, angled slightly anteriorly. Distal radials present at base of rays 2–18, ventralmost at level of proximal radial 3, more ventral rays articulating directly with pectoral cartilage.

Pelvic disc small, length 11.2–18.1 (11.2) % HL, round, about as long as wide, width 10.9–17.4 (13.4) % HL, anterior lobe weakly developed, slightly cupped, distance from snout to pelvic disc 10.0–12.4 % SL. Anus posterior to gill slit, close behind pelvic disc; distance from snout to anus 58.4–89.0 (60.4) % HL.

Principal caudal-fin rays 8–11, dorsal procurrent rays 0–1, ventral procurrent rays 0–1 (0–1 + 4–5/4–6 + 0–1) (1 + 4/4 + 1). Caudal fin length 40.3–57.7 (46.8) % HL. Membrane of posterior dorsal-fin rays attached to caudal fin at shorter distance than anal-fin rays: dorsal-fin rays attached to caudal fin 29.8–59.6 (47.0) % CL; anal-fin rays, 39.1–63.4 (54.8) % CL. Depth at base of caudal fin 11.2–16.3 % CL.

Skin relatively thick, cactus-like prickles more or less covering body, in most dense region about 13 prickles in orbit length. Pyloric caeca 31–34 (31; Burke, 1930), length about 33–53 % HL, center-left side of visceral cavity.

Vertebrae 62–67 (66), precaudal 10–12 (11), caudal 51–56 (55; Tables 2–3). Pleural ribs 2 or 3 (2), anteriormost small when 3, others long and slender, present on vertebrae 8–9 or 9–10 or 10–11 (9–10).

Coloration. Body dusky purple-orange to orangish pink (Fig. 1 B,C). In darker color morphotype (Fig. 1 C), fins dusky, margins dark, lighter anteriorly becoming darker posteriorly; head, dorsum from nape to caudal fin, and ventrum at anal-fin origin to caudal fin dusky purple-orange; isthmus, base of pectoral fin, and body posterior of gill slit to anal-fin origin lighter; area above belly pale to silvery white (guanine) becoming obsolete at about a quarter to half the anal-fin length; base and lower lobe of pectoral fin light with dusky areas; dorsal margin and distal portion of fin dusky; dorsal margin of eye dark, most of eye silvery white. In lighter color morphotype (Fig. 1 B), body and fins orangish pink and white in life; head, dorsum from nape to caudal fin, and ventrum at anal-fin origin to caudal fin orangish pink; isthmus, base of pectoral fin, and body posterior of gill slit to anal-fin origin lighter; area above belly silvery white (guanine) with orangish-pink highlights becoming obsolete at about a quarter to half the anal-fin length; base and lower lobe of pectoral fin white; dorsal margin and distal portion of fin orangish pink; dorsal margin of eye dark, most of eye silvery white. Body and fins dusky to pale in preservation; base of fins beneath skin with pigment, showing faint line between fins and body. Peritoneum pale with scattered speckles; orobranchial cavity pale with scattered speckles; stomach dark, speckled dusky to black; intestines dark, dusky speckled to black; pyloric caeca pale to mottled, and urogenital papilla pale.

Life history. Reaching a maximum size of 350 mm (Okiyama 2004), the largest specimen examined was 264.8 mm (FAKU 131402), a ripe female with yolked eggs. The smallest ripe female with yolked eggs was 194.4 mm. Eggs were 3.6–5.0 mm in diameter. The only ripe male was 229.2 mm.

Distribution. Careproctus trachysoma has been collected from the Sea of Japan, from Hokkaido to off Oki Island, at 150–1345 m (Fig. 6; Okiyama 2004).

Etymology. The specific epithet is derived from the Greek trakhys (τραχύς), meaning “rough”, and soma (σῶΜα), meaning “body”, likely a reference to the covering of cactus-like prickles on the types.

Remarks. We recognize two color morphotypes within C. trachysoma (see Kai et al. 2011a, b). Lighter individuals had either been previously misidentified as C. rastrinus or recognized as a new species, and darker individuals, especially those with dark fins, identified as C. trachysoma (Kido 1988). However, no differences in morphological characters or in mitochondrial or nuclear DNA sequence data have been found between light and dark morphs (Kai et al. 2011a, b).