Careproctus brevipectoralis Chernova, Thiel & Eidus, 2020

Chernova, Natalia, Thiel, Ralf & Eidus, Irina, 2020, Four new species of Careproctus (Cottoidei: Liparidae) from the deep-water vicinity of the southern Kuril Islands (Western North Pacific), Zootaxa 4821 (1), pp. 71-87 : 77-79

Careproctus brevipectoralis Chernova, Thiel & Eidus , new species

English name: Short-finned snailfish

( Fig. 4–5 )

urn:lsid:zoobank.org:act:9CB23AFA-008B-48C3-84CA-C6DA73250689

Holotype: ZMH 26370, TL 164 mm, SL 150 mm, Kuril Basin of the Sea of Okhotsk, 46°56.85´ N, 151°04.92´ E, Agassiz trawl, depth 3300–3301 m, 23 July 2015, R / V “ Akademik M. A. Lavrentyev ”, cruise 71, station 7–12, collector I. Eidus. The specimen is an immature male (stage of maturity II).

Diagnosis. A species of Careproctus with the following combination of characters: vertebrae 55 (10+45), pleural ribs absent. D 49, A 43, P 26, C 9 (principal rays). Hypural unslitted. Head small, 17.7 % SL; preanal length 34.0 % SL. Body deep behind head (119 % lc) and above anal-fin origin (113 % lc), end of tail thin (at about one fifth SL). Eye 26.4 % lc; pelvic disk 41.5 % lc. Pores 2-6-7-1. Pectoral-fin upper lobe short (11.3 % SL), lower lobe slightly longer (13.3 % SL). Grayish brown with reddish tint when fresh. Peritoneum black.

Description. Fresh specimen. Body elliptic in shape, deep and very gelatinous. Tips of dorsal and anal-fin rays protruding from the fin membrane behind the mid-length of body. Lateral line of 20 neuromasts curved in anterior part of body, then following midline being visible on ¾ of tail. Second line of 12 neuromasts present a short distance above former line on a half of body length. Skin grayish-brown with reddish tint, mottled with small dark dots. Head, pectoral fin and base of dorsal and anal fins blackish. Black peritoneum shows through the skin. Margins of the dorsal, anal and caudal fins are light and transparent.

Preserved specimen. Body elliptic, deep and laterally compressed. Preanal distance not large (34.0 % SL) but twice longer than head. Greatest body depth at the anterior third of body length, 4.8 times in SL (excluding height of the dorsal fin, which is hidden in dense tissues). Posteriorly, approximately one fifth of SL, body disproportionately thin.

Head short (5.7 times in SL) and high at nape; head width almost equal to head depth. Snout high, protruding forward over the upper jaw; its front surface is slightly flattened, nasal and anterior infraorbital pores somewhat widened and directed forward. Eye 26.4 % lc, interorbital distance wide (56 % SL). Pupil round. Mouth horizontal, terminal. Oral cleft extending to anterior margin of eye. Teeth simple, in multiple rows; posterior teeth with traces of lateral shoulders and bent into oral cavity. Anterior oblique row on upper jaw with 6 teeth, on lower jaw 5. Gill slit about equal to eye diameter, located completely above pectoral-fin base; upper end of gill slit at level of upper edge of eye, lower end not quite reaching to level of upper pectoral-fin ray. Opercular lobe small and rounded, covering the lower half of gill opening. Cephalic pore pattern 2-6-7-1; the suprabranchial pore located above the very edge of gill opening; chin pores are not brought together.

Radiograph. Vertebrae 55 (precaudal 10, caudal 45), Dorsal-fin rays 49 (precaudal 7), four anterior rays shorter and weaker than the subsequent ones. Anal-fin rays 43, anterior one behind the first haemal spine. Rayless pterygiophores one ( Fig. 5 ), anteriormost dorsal-fin ray inserted between neural spines 4 and 5. Pleural ribs absent. Hypural one, unslitted. C 1+5/4+1; principal rays 9.

Dorsal fin immersed in a dense cartilaginous-like tissue to about middle of SL, completely hidden. In the second half of body, tips of D and A rays protrude from fin membrane (but the rays are soft). Dorsal and anal fins relatively low; their height in anterior half of body less than a third of body height. Pectoral fin with a deep notch separating its lower lobe, consisting of elongated filiform rays. Upper pectoral-fin lobe short (11.3 % SL), not reaching to A-fin origin. Lower lobe slightly longer (13.3 % SL or 118 % of the upper-lobe length), slightly extending beyond anus. Three pectoral notch rays (41 % of the upper-lobe length) slightly spaced, P 26 (16+3+7) in both fins. Dorsalmost pectoral-fin ray at level of infraorbital pores; base of lowermost ray behind posterior margin of eye.

Disk 41.5 % lc, with a dense cartilaginous marginal part and segmented tubercles around the central part. Posterior edge of disk under gill opening. Anus opens twice closer to disk than to anal-fin origin. Anus surrounded unusually by dense tissue.

Skin quite dense, very gelatinous and entirely speckled with small blackish dots; upon closer examination, in some of them, rosettes of tiny needles immersed in skin are noticeable.

In alcohol, skin grayish-brown; head, abdomen and pectoral fins blackish. Disk light. Peritoneum black, oral cavity gray. Blackish bands along bases of dorsal and anal fins not enter the narrowed posterior part of tail.

Distribution. Kuril basin of the Sea of Okhotsk, depth 3301 m.

Environmental conditions. Bottom sediments in the box-corer sample at the place of capture included the upper layer of thin brown silt, and deeper dense greenish silt. The ground from the Agassiz trawl included gray and brown silt. The bycatch was dominated by the holothurians Molpadia sp., Echiura and glass sponges; polychaetes were numerous (not less than 12 species including Travisia sp.). Gorgonians and alcionarians, as well as ascidia of Culeolus sp. and colonies of bryozoans Kinetoskias were few.

Etymology. The name of the species is derived from the Latin words “brevis” (short) and “pectus” (chest, pectoral), since pectoral fins of this species are short compared with other species.

Comparative notes. Absence of pleural ribs, pore number 2-6-7-1, deep and compressed leaf-like body (greatest depth 119 % of lc, depth above A-fin origin 113 %lc), short head (18 % SL) and short pectoral fin (11.3 % SL), cartilaginous-like tissue surrounding the dorsal fin and dense tissue around anus, distinguish the species from other Careproctus of the North Pacific, including the C. laperousi described above.

By the number of vertebrae and fin rays, absence of ribs and by the pore formula, C. brevipectoralis is most similar to C. hyaleius Geistdoerfer which was described from deep-sea hydrothermal vents (Eastern Pacific, 12°48.63’ N, 103°56.41’ W, depth 2630 m) and possess similar counts (vertebrae 54–56, D 48–49, A 43) ( Geistdoerfer 1994; Chernova & Geistdoerfer 2003). The new species differs from the latter by shape of body, black peritoneum (light in the latter), and pigmented skin (vs. the whole body is translucent).

Other North Pacific Careproctus with number of vertebrae 52–61 ( C. rotundifrons Sakurai & Shinohara , C. comus Orr & Maslenikov , C. boversianus Gilbert & Burke , C. batialis , C. marginatus Kido ) differ from C. brevipectoralis in having 2 or 3 pairs of pleural ribs, three-lobed teeth and pore pattern 2-6-7-2. The state of pleural ribs is unknown for C. sinensis Gilbert & Burke , C. zachirus , C. longifilis and C. melanuroides , all having D 51–54, number of vertebrae 55–58 (unknown for C. melanuroides ) and pores 2-6-7-1 (unknown for C. melanuroides ). Careproctus sinensis and C. zachirus differ from C. brevipectoralis in having trilobed or shouldered teeth, larger head (25.7–27.7 % SL) and pale peritoneum. Careproctus longifilis and C. melanuroides posess black peritoneum but differ from C. brevipectoralis in having larger head (22.2–26.3 % SL vs. 18 % SL) and smaller disk (16.1–22.2 and 24.5–25.6 % lc vs. 41.5 % lc).

Figures

FIGURE 4. Careproctus brevipectoralis sp. nov., holotype, ZMH 26370: A, fresh specimen; B–C, preserved specimen.

FIGURE 5. Fragment of the radiograph, Careproctus brevipectoralis sp. nov., holotype, ZMH 26370: in—free interneurale; pleural ribs absent.