Careproctus spinulosus, Kai & Matsuzaki & Mori & Pitruk & Misawa & Tashiro, 2024

Kai, Yoshiaki, Matsuzaki, Koji, Mori, Toshiaki, Pitruk, Dmitry L., Misawa, Ryo & Tashiro, Fumihito, 2024, Snailfishes of the genus Careproctus (Perciformes: Liparidae) with a reduced pelvic disk: three new species and new records from the western North Pacific with comments on their phenotypic diversity, Zootaxa 5492 (2), pp. 191-213 : 201-203

Careproctus spinulosus sp. nov. Kai, Matsuzaki & Mori

New Japanese name: Tomoshibi-bikunin

Fig. 2D , 5 ; Table 1

urn:lsid:zoobank.org:act:440CC240-A352-4A00-84DF-DBCFFCFD44F3

Holotype. FAKU 146600 , 201.0 mm SL, female, off Rausu , Hokkaido, Japan, 44.033ºN, 145.383ºE, 570–825 m depth, F/ V Houyu-maru, Aug. 2018, coll. by Koji Matsuzaki, Shigeki Fujimoto, and Shigetada Fujimoto.

Paratypes. FAKU 146573 , 146574 , 146591 , 105.1 – 190.6 mm SL, 2 males and 1 female, collected with holotype ; FAKU 146631–146632 , 170.6 – 199.8 mm SL, 2 females, off Rausu , Hokkaido, Japan, 500–800 m depth, F/ V Houyu-maru , 10 Sep. 2014, coll. by Koji Matsuzaki, Shigeki Fujimoto, and Shigetada Fujimoto ; FAKU 146900 , male and female, off Rausu, Hokkaido, Japan, 44.023ºN, 145.353ºE, depth unknown, F/ V Houyu-maru , 6 Aug. 2019, coll. by Koji Matsuzaki, Shigeki Fujimoto, and Shigetada Fujimoto ; FAKU 147539 , female, off Rausu , Hokkaido, Japan, depth unknown, F/ V Houyu-maru , 14 Apr. 2020, coll. by Koji Matsuzaki, Shigeki Fujimoto, and Shigetada Fujimoto ; FAKU 147741–147742 , 156.2 + mm SL, 166.3 mm SL, 2 females, off Rausu , Hokkaido, Japan, 600–800 m depth, F/ V Houyu-maru , 20 Jul. 2020, coll. by Koji Matsuzaki, Y. Kai, Shigeki Fujimoto, and Shigetada Fujimoto ; FAKU 147909, 200.4 mm SL, female, 44.024ºN, 145.308ºE, off Rausu , Hokkaido, Japan, 540–750 m depth, F/ V Houyu-maru , Aug. 2020, coll. by Koji Matsuzaki, Shigeki Fujimoto, and Shigetada Fujimoto ; HUMZ 235310 ( FAKU 148864 ), 112.2 mm SL, male, off Rausu , Hokkaido, Japan, 500–800 m depth, F/ V Houyu-maru , Jul. 2021, coll. by Koji Matsuzaki, Shigeki Fujimoto, and Shigetada Fujimoto ; FAKU 148884 , male, 198.8 mm SL, off Rausu , Hokkaido, Japan, 800–1,200 m depth, F/ V Houyu-maru , May 2021, coll. by Koji Matsuzaki, Shigeki Fujimoto, and Shigetada Fujimoto .

Diagnosis. A species of Careproctus with the following combination of characters: vertebrae 55–58; dorsal-fin rays 50–52; anal-fin rays 43–48; pectoral-fin rays 31–36; pectoral fin deeply notched, lower lobe long, same length as or slightly longer than upper lobe, extending to two-thirds between anus and anal fin origin; pelvic disk rounded, greatly reduced; cephalic pores 2-6-7-2, chin pores paired in separate pits; gill slit large, extending ventrally to pectoral-fin rays 6–11; teeth simple, shouldered or weakly trilobed; anus located below posterior rim of orbit; peritoneum and stomach black.

Description. Measurements shown in Table 1 . Paratype data given in parentheses if different from holotype.

Body deep anteriorly, moderately compressed, tapering posteriorly. Skin thick, completely covered by cactus-like prickles; gelatinous tissue under skin well developed. Head large, robust, broadly rounded from nape to snout. Snout rounded, not protruding anterior to mouth. Mouth moderately large, terminal, horizontal; maxilla extending to mid orbit (or slightly shorter); oral cleft extending to anterior rim of orbit. Premaxillary teeth blunt, simple, shouldered or weakly trilobed, arranged in oblique rows of 6 (4–6) teeth per row forming relatively narrow band, inner teeth not enlarged. Mandibular teeth blunt, simple, shouldered or weakly trilobed, arranged in oblique rows of 6 (3–6) teeth per row forming narrow band, inner teeth not enlarged. Narrow diastema at symphysis of upper and lower jaws. Orbit of moderate size, rounded; pupil small and rounded. Nostril single, with short tube, level with mid-orbit (or dorsal part of orbit). Cephalic sensory pores of moderate size: nasal pores 2, maxillary pores 6, preoperculomandibular pores 7, suprabranchial pores 2; cephalic pore pattern 2-6-7-2. Chin pores paired in separate pits, well separated. Coronal pore absent. Gill slit moderately large, upper margin level with mid-orbit, extending ventrally to pectoral-fin ray 6 (6–11). Gill rakers 10, short, with tiny spines on tips (based on FAKU 146632 and FAKU 147742). Opercular flap rounded; tip at level with ventral rim of orbit. Pyloric caeca 20 (14–23), thick and long, covering two-thirds of stomach, on center-left side of visceral cavity.

Vertebrae 55 (55–58), precaudal 9 (9 or 10) and caudal 46 (46–48). Pleural ribs in 2 pairs (1 or 2 pairs), on abdominal vertebrae 8 and 9 (or 9 and 10). Dorsal-fin rays 50 (50–52), not exserted. Anteriormost dorsal-fin pterygiophore rayless, inserted between neural spines 3 and 4 (or 2 and 3). Anal-fin rays 45 (43–48), not exserted. Two (two or three) anal-fin pterygiophores anterior to 1 st haemal spine, each bearing a single ray. Membrane of posterior dorsal- and anal-fin rays attached about equidistant to caudal fin. Caudal fin slightly rounded. Principal caudal-fin rays 8 (8–9), 4(3–4) and 4 (4–5) rays on upper and lower hypurals, respectively, dorsal procurrent rays 1 (rarely absent), ventral procurrent rays absent (or 1). Hypural plates fused with terminal vertebral centrum and parhypural, upper and lower hypural plate separated by narrow slit.

Pectoral fin deeply notched, with 34 (31–36) rays; upper lobe with 21 (21–26) rays, just reaching to (or not reaching) vertical of anal fin origin; lower lobe elongate, with 13 (9–13) rays, 6 th (or 5 th) ray from ventralmost longest, longer than upper lobe, extending to two-thirds between anus and anal-fin origin. Rays in notch more widely spaced than rays of lobes. Tip of pectoral-fin rays of upper lobe slightly protruding, rays of lower lobe strongly exserted. Uppermost pectoral-fin base below level of ventral rim of orbit, level with lower jaw tip. Lowermost pectoral-fin base below anterior half of orbit. Pelvic disk rounded, minute and greatly reduced ( Fig. 5C ). Anus much closer to pelvic disk than to anal fin origin, located below posterior rim of orbit.

Pectoral girdle (based on FAKU 146632: Fig. 2D ): Proximal pectoral radials 3; upper radials 1 and 2 hour-glass shaped, with two notches, placed close to each other; radial 3 rounded squarish, widely separated from upper two radials. Interradial fenestrae 3, extending between scapula and radials 1–2, and below radial 2; fenestra 1 roundish, fenestrae 2 and 3 elliptical. Scapula broadly Y-shaped, with robust helve. Coracoid diamond-shaped, with short thin helve. Distal radials present at base of pectoral-fin rays 2 to 24, absent from base of ventralmost 9 rays.

Coloration: When fresh (based on FAKU 146600), head and body dark reddish, belly somewhat paler. Iris dark, margined with silver. Dorsal, anal, and caudal fins pale red, mottled with dark red; pectoral fin dark red, basal part paler. Pelvic disk white. When preserved, head, body, and fins white. Eyes black. Oral and branchial cavities pale; peritoneum and stomach dark brown (or black).

Reproduction. The holotype (201.0 mm SL) was an immature female. The ovary was whitish, with small rounded eggs less than 0.50 mm diameter. FAKU 146591 (190.6 mm SL) was a spent female with yolked (2.91–3.30 mm diameter) and small immature (less than 0.50 mm diameter) eggs. Yolked eggs were rounded.

Distribution. Known only from the southern Sea of Okhotsk, off Rausu, Hokkaido, Japan, at depths of 500– 1,200 m ( Fig. 3 ).

Etymology. The specific name “ spinulosus ” is derived from the diminutive form of Latin “spina” (spine), in reference to the cactus-like prickles covering the entire body.

Remarks. Among the species with a reduced pelvic disk, C. spinulosus sp. nov. shares a lower pectoral-fin lobe apparently longer than the upper lobe with C. gilberti , but can be distinguished from the latter in having a smaller gill opening, extending ventrally to pectoral-fin rays 5–11 (vs. 14–16), and the body completely covered by cactus-like prickles (vs. smooth, without cactus-like prickles) ( Mecklenburg et al. 2002; see also Remarks under C. sp. cf. gilberti ).

The C. rastrinus and C. reinhardti species groups are also characterized as having a long pectoral fin lower lobe, except for C. acanthodes ( Orr et al. 2015) .As stated above, the members of both species groups have a relatively larger pelvic disk (2.2–9.6% SL) than C. spinulosus sp. nov. (0.4–1.4% SL). The new species can be further distinguished from the former in having a black peritoneum (vs. light or gray) ( Orr et al. 2015). Elassodiscus caudatus ( Gilbert, 1915) and Elassodiscus nyctereutes Kai, Matsuzaki, Orr, Mori & Kamiunten, 2020 mostly resemble the new species in having a long pectoral fin lower lobe, but clearly differ in having trilobed teeth (vs. simple, shouldered or weakly trilobed) ( Kai et al. 2020).

Figures

FIGURE 2. Pectoral girdle in five species of Careproctus with a reduced pelvic disk. Careproctus barbatulus sp. nov., FAKU 146634, paratype, 220.8 mm SL (A); Careproctus barbatulus sp. nov., FAKU 147740, non-type (B); Careproctus longibarbatus sp. nov., FAKU 148477, paratype, 223.0 mm SL (C); C. spinulosus sp. nov., FAKU 146632, paratype, 199.8 mm SL (D); C. mederi, FAKU 148478, non-type, 143.6 mm SL (E); C. gilberti, FAKU S4869, non-type, 67.2 mm SL (F). Shaded areas represent cartilage.

FIGURE 3. Distributional records of species of Careproctus with a reduced pelvic disk based on the present and previous studies (see text).

FIGURE 5. Careproctus spinulosus sp. nov., FAKU 146600, holotype, 201.0 mm SL, fresh condition (A), preserved condition (B), and ventral view of head region (C); ventral view of head region of FAKU 148864, paratype, 112.2 mm SL (D). Dotted red line and arrow indicates position of anus and pelvic disk, respectively.