Careproctus mederi Schmidt, 1916

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 : 203-206

Careproctus mederi Schmidt, 1916

New Japanese name: Agohige-bikunin

Fig. 6 ; Table 2

Careproctus mederi Schmidt 1916: 628 ; figs. 7, 8 (original description; type locality: Sea of Okhotsk, 56.3000ºN, 145.0667ºE, 322 m depth); Schmidt 1950: 215 (description; off Iony Island, northern Sea of Okhotsk); Matsubara 1955: 1193 (key, apparently based on Schmidt 1916; Sea of Okhotsk).

Materials examined. FAKU 146572, 102.3 mm SL, female, off Rausu, Hokkaido, Japan, 44.0373ºN, 145.392ºE, 570–825 m depth , F/ V Houyu-maru, Aug. 2018, coll. by Koji Matsuzaki , Shigeki Fujimoto, and Shigetada Fujimoto . FAKU 148475, 143.6 mm SL, female, off Rausu , Hokkaido, Japan ; FAKU 149138–149139 , 56.2–76.1 mm SL, female and male, Pacific off Hokkaido, 42.7213ºN, 144.3489ºE, 532 m depth , R / V Wakataka-maru .

Diagnosis. A species of Careproctus with the following combination of characters: vertebrae 57–63; dorsal-fin rays 52–56; anal-fin rays 47–52; pectoral-fin rays 27–32; pectoral fin deeply and broadly notched, lower lobe short, reaching to midway between its base and anus; lower part of pectoral girdle protruding anteroventrally below mandible; pelvic disk rounded, greatly reduced; cephalic pores 2-6-7-2, chin pores paired in separate pits; gill slit moderately large, extending ventrally to pectoral-fin rays 6–11; teeth simple or slightly shouldered; anus located below posterior rim of orbit; peritoneum pale with black dots, stomach black ( Schmidt 1916; present study).

Description of Japanese specimens. Counts and measurements shown in Table 2 .

Body moderately deep, compressed, tapering posteriorly ( Fig. 6A ). Skin relatively thick, covered by cactus-like prickles; gelatinous tissue under skin moderately developed. Head moderately large, dorsal profile gradually sloping from nape to snout. Snout rounded, not protruding anterior to mouth. Mouth moderately large, terminal, horizontal; maxilla extending to mid orbit; oral cleft extending to anterior rim of orbit. Premaxillary teeth sharp, simple, arranged in oblique rows of 5–8 teeth per row forming relatively narrow band, inner teeth enlarged. Mandibular teeth sharp, simple, arranged in oblique rows of 4–8 teeth per row forming narrow band, inner teeth not enlarged. Diastema at symphysis of upper jaws V-shaped, wider anteriorly, that of lower jaws narrow ( Fig. 6C ). Orbit of moderate size, rounded; pupil rounded. Nostril single, with short tube, level with mid-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 rays 6–11. Gill rakers 9 or 10, short, with tiny spines on tips. Opercular flap rounded; tip level with ventral rim of orbit. Pyloric caeca 9–12, thick, covering half of stomach, on center-left side of visceral cavity.

Vertebrae 61–63, precaudal 9–10 and caudal 51–53. Pleural ribs in 1 pair on abdominal vertebrae 9 or absent. Dorsal-fin rays 55–56, not exserted. Anteriormost dorsal-fin pterygiophore inserted between neural spines 3 and 4 or 4 and 5, bearing a single ray. Anterior rayless pterygiophore present or absent. Anal-fin rays 50–52, not exserted. One or two anal-fin pterygiophore 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 or truncated. Principal caudal-fin rays 8–9, 4 and 4–5 rays on upper and lower hypurals, respectively, dorsal procurrent rays 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 and broadly notched, with 30–32 rays; upper lobe with 15–19 rays, reaching to anal-fin ray 1–4; basal part of 5–7 rays in notch adhering to body skin, tips free: lower lobe short, with 8 rays, 4 th or 5 th ray from ventralmost longest, reaching to midway between its base and anus. Rays in notch more widely spaced than rays of lobes. Uppermost pectoral-fin base level with corner of mouth. Lowermost pectoral-fin base below region between snout and anterior rim of orbit, lower part of pectoral girdle protruding anteroventrally below mandible. Pelvic disk rounded, minute, located below mid orbit. Anus much closer to pelvic disk than to anal fin origin, located below posterior rim of orbit.

Pectoral girdle (based on FAKU 148478: Fig. 2E ): Proximal pectoral radials 4; upper radials 1 and 2 hour-grass shaped with two notches; radial 3 rounded; radials 1–3 closely positioned to each other; radial 4 rounded squarish, widely separated from radials 1–3. Interradial fenestrae 3, extending between scapula and radials 1–2, and below radial 2; fenestra 1 roundish, fenestrae 2 and 3 elliptical, latter small and slit-like. 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 7 rays.

Coloration: Fresh coloration unknown. When preserved, head, body, and fins white. Distal part of dorsal and anal fins dark. Eyes black. Oral and branchial cavities pale; peritoneum pale with black dots, stomach black.

Reproduction. FAKU 146572 (102.3 mm SL) was a female with elliptical yolked eggs, large-axis diameter ranging from 5.66–6.00 mm and short-axis diameter from 2.98–3.39 mm ( Fig. 6B ).

Distribution. The syntypes were collected from near Iony Is., northern Sea of Okhotsk. Additional specimens from the same locality were reported by Schmidt (1950). Since then, no other records are known, except for Kido’s (1988) specimens, which are described herein as C. longibarbatus sp. nov. The present specimens were collected from Rausu, Hokkaido, southern Sea of Okhotsk, and Kushiro, Pacific coast of Hokkaido, Japan, the latter representing the southernmost record of the species. Known from depths between 202–825 m ( Schmidt 1950; this study).

Remarks. The syntypes of C. mederi (ZIN 18958) are characterized by the following characters: vertebrae 57–59; dorsal-fin rays 52–53; anal-fin rays 47–49; pectoral fin deeply and broadly notched, lower lobe short; pelvic disk minute, 1.0–1.2% of SL; cephalic pores 2-6-7-2, chin pores paired in separate pits; gill slit moderately large, extending ventrally to pectoral-fin rays 10–12; body completely covered with cactus-like prickles ( Schmidt 1916; this study) ( Fig. 6D–F ). The present specimens from the southern Sea of Okhotsk agreed with the syntypes in having a small pelvic disk 0.7–1.4% of SL, a short pectoral fin lower lobe, not reaching the anus, and the body covered with cactus-like prickles. In addition, both the syntypes and present specimens had the pectoral girdle protruding anteroventrally below the mandible ( Fig. 6 ). One of the syntypes (150.0 mm SL) was a female with elliptical yolked eggs, of similar size and shape to those of FAKU 146572 ( Fig. 6E ). Owing to these similarities, the present specimens were identified here as C. mederi , despite their counts of vertebrae, dorsal- and anal-fin rays, and pyloric caeca being somewhat different from those of the syntypes. Such are considered here as geographic variations ( Table 2 ). The new Japanese name "Agohige-bikunin" is proposed here on the basis of FAKU 146572.

The pectoral girdle morphology, protruding anteroventrally, in C. mederi was also seen in C. ostentum and C. parvidiscus ( Fig. 7A, B ). Careproctus mederi is more similar to C. ostentum , which has 51–56 dorsal- and 47–51 anal-fin rays, 8–13 pyloric caeca, a small pelvic disk, ca. 1.6% of SL, a moderately large gill slit, extending ventrally to pectoral-fin rays 8–16, a deep and broadly notched pectoral fin, black stomach, pale peritoneum with black dots, and elliptical eggs ( Gilbert 1896; Burke 1930; Mecklenburg et al. 2002; this study). However, C. mederi is distinguished from C. ostentum by its lighter body coloration (dark in C. ostentum : Fig. 7A ) and COI haplotypes ( Fig. 8 ), although further morphological and genetic information may support the synonymization of the two species. For the present, however, the two species are conservatively recognized as valid. In contrast, C. parvidiscus can be readily distinguished from C. mederi in having 50 dorsal- and 44 anal-fin rays, and extremely deciduous cactus-like prickles on the body (vs. 52–56 dorsal- and 47–52 anal-fin rays, and the body with strong cactus-like prickles) ( Imamura and Nobetsu 2002; this study).

Comparative materials. Careproctus mederi : ZIN 18958 (X-rays only), 4 specimens, syntypes, 108.0–152.0 mm SL, 56.300ºN, 145.067ºE, off Iony Island , northern Sea of Okhotsk, 322 m depth , 28 Aug. 1914, coll. by G. R. Meder. Careproctus ostentum : FAKU 120225 , 120227–120229 , 4 females, 74.2–80.9 mm SL, Aleutian Is., 52.550ºN, 179.950ºE, 279 m depth ; HUMZ 82565–82567 , 48.0– 66.6 mm SL, 2 males and female, Aleutian Is., 59.328ºN, 178.112ºW, 610 m depth ; USNM 48619 (photo and X-ray photo), lectotype, damaged, north of Unalaska Is. , USA, 53.564ºN, 167.781ºW, 199 m depth ; UW 119726 , 97.7 mm SL, sex undetermined, Bering Sea, 59.398ºN, 177.670ºW, 332 m depth ; UW 150870 , 72.1 mm SL, sex undetermined, Aleutian Is., 51.717ºN, 177.294ºE. Careproctus parvidiscus : HUMZ 164407 , holotype, 167.7 mm SL, male, off Shiretoko Point, Hokkaido, Japan, southern Sea of Okhotsk, 400–700 m depth , bottom gill net, 12 May 1997, coll. by T. Nobetsu .

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 6. Careproctus mederi, FAKU 146572, 102.3 mm SL, (preserved) (A); diastema at symphysis of upper jaw of FAKU 148478, 143.6 mm SL (B); eggs of FAKU 146572 (C); one of four syntypes of ZIN 18958, 150.0 mm SL, (preserved) (D), eggs (E), and ventral view of head region (F). Dotted red line and arrow indicates position of anus and pelvic disk, respectively.

FIGURE 7. Careproctus gilberti and related species. Careproctus ostentum, UW 150870, 72.1 mm SL, (preserved) (A); C. parvidiscus, HUMZ 164407, holotype, 167.7 mm SL, (preserved) (B); Careproctus sp. cf. gilberti, FAKU 147753, 55.1 mm SL, (preserved) (C); C. gilberti, OS 8684, 69.2 mm SL, (preserved) (D), and ventral view of head region of OS 8684 (E).

FIGURE 8. (A): Neighbor-joining (NJ) tree of the Careproctus gilberti, C. rastrinus, and C. reinhardti species groups based on sequence variations in the mitochondrial COI (474 bp) gene. Support values (≥50% ML bootstrap probability) indicated along branches. Each node labeled with collection registration number (sequences determined here) or INSDC accession number (sequences determined in previous studies, in italics). (B): A minimum spanning network of the C. gilberti species group. Each circle represents a unique haplotype; area of each circle proportional to number of individuals; each bar on internal nodes represents a single nucleotide change. In addition to the sequences determined here, the following sequences from INSDC were used. Careproctus ostentum: MH715573, KU053754; C. gilberti: MH630293, KU053753, MH715534–MH715569, MH882481, JQ354029, MH630294.