Careproctus acanthodes Gilbert & Burke 1912

Careproctus acanthodes Gilbert & Burke 1912

English common name: Toge Snailfish

Japanese common name: Toge-bikunin Figures 2 A, 5D, 6; Tables 1–3

Careproctus acanthodes Gilbert & Burke 1912:363, pl. 43, fig. 3. Type locality: Tatar Strait, 47°38'40"N, 141°24'30"E.— Burke 1930:135, fig. 56 (description, key).— Soldatov & Lindberg 1930:25 (Tatar Strait, key).— Chapman & DeLacy 1934:3 (comparisons).— Taranetz 1937:137 (Tatar Strait, key).— Okada & Matsubara 1938:346 (Gulf of Tartary).— Schmidt 1950:210 (description, Tatar Strait, west off Kamchatka Peninsula).— Böhlke 1953:135 (type catalog).— Matsubara 1955:1193 (Tartar Strait).— Ueno 1971:97 (Sakhalin, Russia).— Quast & Hall 1972:28 (near Alaska).—Kido 1984:339, pl. 365-H (Tatar Strait).— Lindberg & Krasyukova 1987:441 (Tatar Strait, Sea of Okhotsk).— Kido 1988:217 (considered C. acanthodes a synonym of C. rastrinus).— Pitruk 1990:36 (list, Sea of Japan).—Sokolovskaya et al. 1998:11 (Sea of Japan).— Sheiko & Fedorov 2000:32 (considered C. acanthodes a synonym of C. rastrinus).— Mecklenburg et al. 2002:611 (considered C. acanthodes a synonym of C. rastrinus).— Chernova et al. 2004:4 (checklist).— Chernova 2005b:S7 (comparisons).—Love et al. 2005 (C. acanthodes valid).— Kai et al. 2011a:144 (genetics, morphology, phylogenetics, as SOJ3).— Kai et al. 2011b:368 (fig. 1a, phylogenetics, as SOJ3).— Shinohara et al. 2011:47 (Sea of Japan).— Shinohara et al. 2014:256 (Sea of Japan).

Holotype. USNM 73332, 75.9 mm, Russia, Tatar Strait off southwestern coast of Sakhalin Island, Albatross station 4997, 47.6444°N, 141.4083°E, depth 581 m, 23 September 1906.

Paratypes. SU 22236, 4 (32.9–50.7 mm), same locality data as for holotype.

Additional material examined. A total of 24 specimens, not including the types above, 68.3–104.7 mm SL. See “Non-type material examined below.”

Diagnosis. Careproctus acanthodes is distinguished from all other species of Careproctus by the combination of cyt b and 16S rRNA sequences (“SOJ3” of Kai et al. 2011a; Table 1), a slender body covered by cactus-like prickles, a broad interorbital, the presence of the postorbital pore, a moderate-sized pelvic disc, a lower pectoral-fin lobe shorter than upper lobe, and a light peritoneum. It is most similar to C. pellucidus of the western Pacific, from which it is further distinguished by its larger pelvic disc (18.2–28.8 % HL in C. acanthodes vs. 10.0–17.0 % HL in C. pellucidus), shorter lower pectoral-fin lobe (35.7–61.2 vs. 57.2–128.8 % HL), longer nasal tube (2.0–6.2 vs 0.1– 2.6 % HL), and fewer gill rakers (7–10 vs. 10–13). It is also similar to C. rastrinus and light colored C. trachysoma, from both of which it can be distinguished by its shorter lower pectoral-fin lobe (35.7–61.2 vs. 52.6–141.9 % HL), longer nasal tube 2.0–6.2 vs 0.1–4.7 % HL), and lower counts of median fin rays (dorsal 52–55, anal 44–49 in C. acanthodes vs. 57–63 and 51–57 in C. rastrinus and C. trachysoma) and total vertebrae (56–61 vs. 62–67). From C. phasma, it can be distinguished by the postorbital pore (present vs absent in C. phasma), broader interorbital (fleshy distance 42.9–72.8 vs. 19.6–52.5 % HL), and shorter lower pectoral-fin lobe (35.7–61.2 vs 60.3–134.6 % HL). From C. scottae, it can be distinguished by its shorter lower pectoral-fin lobe (35.7–61.2 vs 54.2–132.6 % HL), lower counts of dorsal-fin rays (52–55 vs 54–61 in C. scottae), anal-fin rays (44–49 vs 47–53), and vertebrae (56–61 vs. 59–64). It is further distinguished from C. spectrum by its smaller orbit (24.0–33.9 vs. 33.9–34.4 % HL).

Description. Body small, maximum size examined 104.7 mm SL, relatively slender, tapering posteriorly, anteriorly rounded in cross section; depth at pectoral-fin base 80.2–107.1 (86.0) % HL. Head moderate, 24.5–27.0 (27.0) % SL, dorsal profile rounded from nape to snout. Snout blunt and short, slightly projecting anterior to lower jaw. Mouth terminal, small, horizontal; upper jaw 40.3–47.1 (40.8) % HL, maxilla extending to mid-orbit, oral cleft extending to anterior rim or anterior part of orbit; mandible 42.8–50.0 (48.9) % HL. Premaxillary tooth plates matching mandibular tooth plates. Premaxillary and mandibular teeth simple with weak shoulders in 29–33 oblique rows of 7–9 teeth forming narrow bands. Diastema absent at symphysis of upper and lower jaws. Orbit 24.0–33.9 (32.7) % HL, dorsal margin well below dorsal contour of head, suborbital depth to upper jaw 25.6–75.8 (52.3) % OL, 6.5–19.0 (17.1) % HL; pupil round. Interorbital space broad, fleshy distance 42.9–72.8 (46.5) % HL, bony distance 14.5–29.9 (22.0) % HL, strongly convex. Snout longer than orbit, 87.8–154.6 (91.1) % OL, 27.3–39.5 (34.3) % HL. Nostril single, with well-developed tube at level with mid-orbit; nostril tube length 7.4–25.8 % OL.

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

Gill opening large, 18.2–36.1 (24.4) % HL, upper margin at mid-orbit or level with dorsal rim of orbit, extending ventrally to pectoral-fin rays 1–5 (ray 2). Opercular flap rounded to slightly angular (rounded). Gill rakers 7–10 (Tables 2–3), short, blunt.

Dorsal-fin rays 52–55 (53; Tables 2–3), anterior dorsal lobe absent, anterior rays buried in tissues, tips of more posterior rays not exserted. Anteriormost dorsal-fin pterygiophore inserted between neural spines 2 and 3 or 3 and 4, rayless or bearing a small ray (between 3 and 4, rayless). Predorsal length 26.3–32.6 (32.6) % SL. Anal-fin rays 44–49 (49; Tables 2–3), one to two anal-fin pterygiophores anterior to first haemal spine (one), each bearing a single ray (anterior ray in holotype apparently split), tips of all rays exserted. Anal-fin origin below vertebrae 12– 13 (caudal vertebrae 2–3), preanal length 33.4–45.2 (33.4) % SL.

Pectoral fin deeply notched, with 29–36 (33) rays (Tables 2–3). Upper lobe 48.3–75.1 (67.3) % HL, with 22– 30 (27) rays extending to or beyond anal-fin origin, longer than lower lobe, dorsalmost rays lengthening to rays 4– 6, more ventral rays gradually shortening to shortest ray of notch. Lower lobe moderately elongate, 35.7–61.2 (39.9) % HL, with 6–8 rays (8), extending between anus and anal-fin origin; dorsal rays gradually lengthening to elongate rays 2–5, ventral rays gradually shortening to ventralmost ray near pectoral symphysis. Tips of rays 5– 30% free of membrane, rays of lower lobe more strongly exserted, up to 30% free of membrane in longest ray. 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 placed anteriorly, at level between snout and anterior rim of orbit. Proximal pectoral radials four (3+1), robust: radials 1–2 notched and hour-glass shaped, radial 3 crescent shaped, radial 4 round (Fig. 5 D). Interradial fenestrae three, extending between scapula and proximal radials 1–3: fenestra 1 crescent shaped, 2 oval, 3 dorsoventrally elongate. Scapula broadly T-shaped, with long robust arms and shorter robust helve, broad notch between base of helve and anterior extension of basal cartilage; coracoid with broad triangular head and short, robust helve. Distal radials present at base of all rays except the dorsal- and ventralmost.

Pelvic disc of moderate size, length 18.2–28.8 (19.0) % HL, round, about as long as wide, width 16.9–30.2 (21.9) % HL, anterior lobe weakly to moderately developed, slightly cupped, distance from tip of snout to pelvic disc 11.7–14.9 (12.3) % SL. Anus at level just posterior to orbit, close behind pelvic disc; distance from snout to anus 16.8–22.5 (16.8) % SL, 62.2–91.8 (62.2) % HL.

Principal caudal-fin rays 9, dorsal procurrent rays 1–2, ventral procurrent rays 0 (1–2 + 4/5 + 0) (2 + 4/5 + 1). Caudal fin 36.1–47.1 (41.7) % HL. Membrane of posterior dorsal-fin rays attached for a shorter distance to caudal fin than anal-fin rays: dorsal-fin rays attached to caudal fin 21.5–47.3 (33.3) % CL; anal-fin rays, 32.0–52.1 (42.7) % CL. Depth at base of caudal fin 6.7–18.5 (17.3) % CL.

Skin relatively thick, thin gelatinous layer beneath skin, cactus-like prickles covering body, in most dense region about 10 prickles in orbit length. Pyloric caeca 19, length about 73 % HL, left side of visceral cavity.

Vertebrae 56–61 (58), precaudal 9–11 (9), caudal 47–51 (49; Tables 2–3). Pleural ribs 2 or 3 (2), when 3 anteriormost small, others long and slender, present on vertebrae 6–7, 7–8, 8–9, or 7–9 (7–8).

Coloration. Body and fins dusky orangish pink and white to dusky in life; head, dorsum from nape to caudal fin, and ventrum at anal-fin origin to caudal fin dusky orangish pink; isthmus, base of pectoral fin, and body posterior of gill slit to anal-fin origin lighter; area above belly silvery white (crystalline guanine) becoming obsolete at anal-fin origin; base and lower lobe of pectoral fin white, dorsal margin and distal portion of fin dusky; base of dorsal and anal fins pigmented along body margin; eye dark dorsally, silvery ventrally. Body and fins pale in preservation; base of fins beneath skin with pigment, showing faint line between fins and body. Peritoneum pale; orobranchial cavity pale; stomach pale to white, intestines pale, pyloric caeca pale, and urogenital papilla pale.

Life history. The largest specimen examined was 104.7 mm (FAKU 130974), a ripe female. The smallest ripe female with yolked eggs was 81 mm. Egg diameters of yolked eggs were 2.3–3.7 mm.

Distribution. Careproctus acanthodes has been collected from the eastern Sea of Japan, in the Gulf of Tatary off the southwest coast of Sakhalin Island, and in the Sea of Okhotsk off Cape Patience (Fig. 6), and off the west coast of Kamchatka (Lindberg and Krasyukova 1987). Collection depths range from 114 m to 582 m at the type locality.

Etymology. The specific epithet is derived from the Greek word akanthodes (ἀκανθὼδης), meaning “spiny form”, a reference to the cactus-like prickles covering the bodies of the cotypes.

Remarks. Schmidt (1950) described three specimens of C. acanthodes taken in the northern Sea of Okhotsk off the western coast of Kamchatka. While noting their capture far north of the type locality in the Tatar Strait, he listed meristic data that differed from the description of type material. Although his counts of 30–31 (24–25/6) pectoral-fin rays are well within the range of our material, his counts of 55–57 dorsal- and 50–54 anal-fin rays are higher than nearly all of our material examined (six of our specimens had 55 dorsal-fin rays, all others had fewer), suggesting that he may have misidentified another species.