Careproctus brevipectoralis Chernova, Thiel &Eidus, 2020

Kai, Yoshiaki, Endo, Hiromitsu, Tashiro, Fumihito & Nakayama, Naohide, 2021, Two new species of snailfishes of the genus Careproctus (Cottoidei: Liparidae) from the western North Pacific Ocean with a range extension of Careproctus brevipectoralis, Zootaxa 4951 (2), pp. 361-371 : 368-369

publication ID	https://doi.org/ 10.11646/zootaxa.4951.2.9
publication LSID	lsid:zoobank.org:pub:942E67E4-6A3E-4AFE-8911-2AF58A0F92DD
DOI	https://doi.org/10.5281/zenodo.4683534
persistent identifier	https://treatment.plazi.org/id/03826F0F-FFC4-E075-FF2B-D5E30431FADA
treatment provided by	Plazi
scientific name	Careproctus brevipectoralis Chernova, Thiel &Eidus, 2020
status

Treatment

English name: Short-finned snailfish; New Japanese name: Nezumi-kon’nyaku-uo

Figs. 1E View FIGURE 1 , 2C, 2F View FIGURE 2 , 3C View FIGURE 3 ; Table 1 View TABLE 1

Careproctus brevipectoralis Chernova, Thiel & Eidus, 2020: 77 View Cited Treatment , figs. 4–5 (type locality: Kuril Basin GoogleMaps of the Sea of Okhotsk, 46.948ºN, 151.082ºE, 3,300–3,301 m).

Specimen examined. BSKU 96445, 194.6 mm SL, male, 39.5530ºN, 143.4168ºE, off Iwate, Japan, 2,388–2,433 m depth ( KT08-27 , St. M-3) GoogleMaps , R / V Tansei-maru , 22 Oct. 2008, coll. by Hiromitsu Endo and Naohide Nakayama .

Diagnosis. A species of Careproctus with the following combination of characters: vertebrae 55–56; dorsal-fin rays 49–51; anal-fin rays 43–44; pectoral-fin rays 26–28; pectoral fin with distinct notch; cephalic pores 2-6-7-1, chin pores well separated; gill slit entirely above pectoral fin; pleural ribs absent; peritoneum dark, stomach white ( Chernova et al. 2020; this study).

Description of Japanese specimen. Counts and measurements are shown in Table 1 View TABLE 1 . Body elliptic and deep, compressed, tapering posteriorly, deepest at origin of dorsal fin ( Fig. 1D View FIGURE 1 ). Skin thin, fragile, lacking prickles. Head compressed, dorsal profile rounded from nape to snout. Snout blunt, rounded, with thick gelatinous tissue, projecting anterior to lower jaw. Mouth moderately large, subterminal; maxilla extending to middle of orbit; oral cleft extending to anterior rim of orbit. Premaxillary teeth simple, inner teeth weakly shouldered, in 6 oblique rows; inner teeth of anterior portion of premaxillary weakly trilobed teeth ( Fig. 2C View FIGURE 2 ). Mandibular teeth simple, inner teeth weakly shouldered, in 6 oblique rows. A narrow diastema present at symphysis of upper and lower jaws. Orbit rounded, relatively small. Nostril single, with short tube at level with middle of orbit. Cephalic sensory pores moderate size: nasal pores 2, maxillary pores 6, preoperculomandibular pores 7, suprabranchial pore 1; cephalic pore pattern 2-6-7-1. Chin pores well separated ( Fig. 3C View FIGURE 3 ). Gill slit completely above pectoral-fin base, almost equal to eye diameter; upper margin of gill slit at level with dorsal rim of orbit and lower margin with ventral rim of orbit. Gill rakers 9, flattened and undeveloped. Opercular flap slightly rounded posteriorly. Pyloric caeca 14, on centerright side of visceral cavity.

Vertebrae 56 (9+47). Pleural ribs absent. Dorsal-fin rays 51. Anteriormost dorsal-fin pterygiophore without ray, pterygiophore with anteriormost dorsal-fin ray inserted between neural spines 3 and 4; dorsal-fin origin between levels of opercle and anus. Anal-fin rays 44; anal-fin origin below 8th dorsal-fin ray. One anal-fin pterygiophore anterior to first haemal spine bearing a single ray. Membrane of posterior dorsal- and anal-fin rays attached about equidistant on caudal fin. Caudal fin truncate. Principal caudal-fin rays 9 (5 on upper and 4 on lower hypural plate), single dorsal and anal procurrent rays present. Hypural plates fused with terminal vertebral centrum, upper and lower hypural plate separated by a narrow slit.

Pectoral fin short, rounded, with 28 rays, 5 th ray from uppermost longest, reaching to midway between anus and anal-fin origin; deep notch present, rays in notch slightly more widely spaced than rays of lobes; rays of lower lobe exserted, longest ray of lower lobe extending to midway between posterior rim of pelvic disk and anus. Uppermost pectoral-fin base level with tip of snout; symphysis of pectoral-fins below posterior rim of orbit. Pectoral radials 4, of moderate, rounded, arranged at nearly equal intervals ( Fig. 2F View FIGURE 2 ). No interradial fenestrae between proximal radials. Scapula broad with robust helve, posteroventral margin rounded. Coracoid triangular with long thin helve and broad lamina. Distal radials present at base of all pectoral-fin rays, except for uppermost ray and lower 3 rays. Pelvic disk of moderate size, round, below region between posterior rim of orbit and gill slit. Anus about midway between pelvic disk and anal-fin origin, somewhat closer to pelvic disk.

Coloration: When fresh, head, nape, and belly blackish; ventral side of head gray; body posterior to anus pale gray or pink ( Fig. 1E View FIGURE 1 ). Dorsal and anal fins colorless, distal margins black; caudal fin colorless, uppermost and lowermost rays black; pectoral fin colorless; pelvic disk gray margined with black. Eye black. When preserved, head and belly dark brown; nape brown; ventral side of head pale brown; body posterior to anus pale brown (skin mostly damaged). Fins white; pelvic disc margined with dark brown. Peritoneum and branchial cavity black; oral cavity pale; stomach white.

Distribution. Western Pacific Ocean, Kuril Basin of the Sea of Okhotsk and off the Pacific coast of Tohoku District, northern Honshu Is., Japan, in depths of 2,388 –3,301 m ( Chernova et al. 2020; this study).

Remarks. Chernova et al. (2020) described their new species, Careproctus brevipectoralis , on the basis of a single specimen from the Kuril Basin of the Sea of Okhotsk at the depth of 3,300 –3,301 m. The present specimen agreed well with C. brevipectoralis in having a cephalic pore pattern of 2-6-7-1, chin pores in separated pits, no pleural ribs, a short pectoral fin, not reaching to anal-fin origin, and a gill slit completely above the pectoral fin. Furthermore, counts and measurements of the present specimen roughly matched those of the holotype of C. brevipectoralis ( Table 1 View TABLE 1 ). Chernova et al. (2020) described the holotype as having simple teeth, some with lateral shoulders, and no slit between the upper and lower hypural plate, while our specimen has simple or weakly shouldered teeth on both jaws, except for the anterior portion of premaxillary with weakly trilobed teeth, and a narrow slit between upper and lower hypural plate. Tooth patterns and shapes are useful to distinguish snailfish species (e.g., Stein 1978; Kido 1988), but sometimes can vary with ontogeny ( Orr 2012) or by the position on the tooth plate ( Kido & Shinohara 1997; Sakurai & Shinohara 2008; Murasaki et al. 2019b). We regard differences between our specimen and the holotype as intraspecific variations, and identified the present specimen as C. brevipectoralis , representing the second and southernmost record of the species.

Comparisons with other species of Careproctus are well described in Chernova et al. (2020). Among the species of Careproctus known from the North Pacific, Chernova et al. (2020) described the differences between C. brevipectoralis and four other species having a cephalic pore pattern of 2-6-7-1 and similar counts in vertebrae and fin rays: Careproctus sinensis Gilbert & Burke, 1912 , Careproctus longifilis Garman, 1892 , Careproctus melanuroides Schmidt, 1950 , and Careproctus zachirus Kido, 1985 . Although Chernova et al. (2020) noted that the presence or absence of pleural ribs as unknown for these species, the holotypes of C. sinensis and C. zachirus have pleural ribs and are clearly distinguishable from C. brevipectoralis (see Matsuzaki et al. 2020; this study).