Careproctus laperousei 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 : 73-76

Careproctus laperousei Chernova, Thiel & Eidus , new species

English name: Laperouse snailfish

( Fig. 1–2 ; Tables 1–2)

urn:lsid:zoobank.org:act:7A8265FB-E629-4391-A273-39677385D59F

Holotype: ZMH 26369, 136 mm TL, 120 mm SL, the northern slope of the Kuril-Kamchatka Trench, 46°06.502´ N, 152°14.139´ E, Agassiz trawl, depth 4803– 4796 m, 29 July 2015, R / V “ Akademik M. A. Lavrentyev ”, cruise 71, station 10–8, collector I. Eidus. The holotype is an immature female (stage of maturity II).

Diagnosis. A species of Careproctus with the following combination of characters: vertebrae 57 (11+46). Pleural ribs 2 pairs. D 53, A 45, P 26, C 8 (principal rays). Hypural one, slitted. Head length 22.5 % SL, preanal length short, 31 % SL. Eye not large, 16.7 % lc, disk 37.0 % lc. Opercular flap angular, protruding. Pores 2-6-7-1. Pectoralfin length 20 % SL. Grayish-brown with a pink tint when fresh. Peritoneum black.

Description. Fresh specimen. Head widely rounded, snout somewhat flattened. Greatest depth behind occiput. Caudal part of body becoming noticeably less deep at the middle of its length; translucent at the end. Skin slippery, moderately gelatinous. Body grayish-brown, with a pink tint. Black peritoneum showing through the body wall. Marginal part of the disk uncolored. Head, pectoral and unpaired fins blackish. Skin around the anus and genital opening light.

Preserved specimen. Dorsal contour of the body arched; ventral contour almost straight. The body height 63 % lc, contained 7.1 times in SL. Head not large, 4.4 times in SL, but rather massive; its width (70 % lc) greater than the height (63 % lc). Dorsal contour rounded to the tip of snout. Snout gelatinous, distinctly protruding above the lower jaw, 2.2 times as large as eye. Nostril looks as a pore with a raised edge, at the level of the upper edge of eye. Eye small, less than 1/5 of head length. Mouth inferior. Lower jaw slightly shorter than the upper jaw, so the edge of maxillary dental patch is visible when looking at head from below. Oral cleft extending to anterior rim of pupil. Teeth simple, elongated, in oblique rows; 5–6 teeth in a full row in front of jaws. Gill opening completely above the pectoral-fin base, reaching down to the upper ray; 1.7 times longer than eye diameter. Opercular flap large, angular and protrudes markedly back (as a result, head length is larger than predorsal length). Length of operculum is 2 times that of the eye. Cephalic pore pattern 2-6-7-1. Pores small, chin pores slightly brought together.

Radiograph. Vertebrae 57 (precaudal 11, caudal 46). Dorsal-fin rays 53 (precaudal 9), anal-fin rays 45, anterior one before the first haemal spine. Rayless pterygiophores absent; anteriormost dorsal-fin ray inserted between neural spines 3 and 4. Pleural ribs in 2 pairs on 8th and 9th vertebrae ( Fig. 2 ). Hypural one, slitted. C 1+4/4+0, principal rays 8; the single secondary ray sits on the dorsoposterior third of hypural.

Dorsal-fin origin above the base of pectoral fin. Dorsal fin low, in anterior half of length its height does not exceed a half of the body height. Anal fin is lower than the dorsal fin. Dorsal and anal fins overlap caudal fin at about 1/5th of its length.

Pectoral fin with 26 rays, subdivided in two lobes. Upper lobe long (20 % SL and 89 % lc), with 19 thin rays, reaching to anal-fin origin. Lower lobe shorter (67 % of the upper lobe length), with 7 rays, free tips of which protrude from fin membrane. There is lack of shortened rays or wider ray spacing in the transition between two pectoral lobes (clear fin notch absent). Dorsalmost pectoral-fin ray at level of infraorbital pores, symphysis of pectoral fins located below posterior margin of eye.

Pelvic disk 2.2 times larger than eye, flattened; anterior lobe well defined, marginal part thin and not cartilaginous, translucent; segmented tubercles around the central part absent. Disk located immediately behind the pectoral symphysis; its posterior edge approximately below the end of the opercular lobe. The distance from chin to anterior margin of disk equal to disk length. Anus opens slightly closer to disk than to anal-fin origin. Distance from posterior margin of disk to anus larger than eye, distance from anus to anal-fin origin less than disk length. Skin thin, translucent, naked and slightly gelatinous.

In alcohol, pinkish pigmentation disappears. Body and bases of unpaired fins remain light (muscles and rays show through the skin). Head, abdomen and margins of unpaired fins blackish. Peritoneum black. The oral cavity, pores, disk and anus uncolored.

Distribution. The northern slope of the Kuril-Kamchatka Trench, depth 4796–4803 m. The Laperouse snailfish was collected at the greatest depths of all species of Careproctus in the North Pacific.

Environmental conditions. Bottom sediments in the box-corer sample at the place of capture included an upper layer of thin gray silt, dense greenish silt and coarse-grained black sand. The ground from the Agassiz trawl included greenish clayey silt interspersed with dense clay. The bycatch was dominated by the holothurian Peniagone sp., Sea feather Umbelulla sp., Scleractinia, sea anemones, sipunculids, polychaetes Travisia sp. and three types of Echiura.

Etymology. The species is named after the French Naval officer and seafarer J.F. Laperouse (Chevalier JeanFrançois de Galaup, comte de La Pérouse) (1741— ca. 1788), who made a geographical expedition to the Pacific Ocean and discovered the Bussol Strait in 1787.

Comparative notes. A characteristic disk with muscle reduction has been described for species of the genus Osteodiscus Stein ( Fig. 3 ). One of the representatives, O. andriashevi Pitruk & Fedorov , is known from the Sea of Okhotsk (depth 1745–1950 m) ( Pitruk & Fedorov 1990). Our specimen is assigned to the genus Careproctus , since it differs from Osteodiscus by lesser disk reduction (in Osteodiscus the musculature and cartilaginous margin of the disk are absent, pelvic rays are covered by transparent skin). Other differences include the presence of 2 pairs of pleural ribs (absent in Osteodiscus ), the structure of the hypural plate (unslitted and fused with the ural center in the latter), and also not a whip-like posterior part of the body.

Careproctus laperousei clearly differs from most of deep-water congeners of the North Pacific ( C. bathycoetus , C. batialis , C. cypselurus , С. lycopersicus , C. surugaensis and C. notosaikaiensis Kai, Ikeguchi & Nakabo ) in the presence of one or more significantly different characters (vertebrae or fin rays counts, head or disk size, pore pattern, teeth shape, color patterns) ( Jordan & Gilbert in Jordan & Evermann 1898; Gilbert & Burke 1912 a; Popov 1933; Kido 1983, 1988; Kai et al. 2011; Orr 2012; Murasaki et al. 2017).

By a combination of counts (vertebrae 57, P 26, C principal 8, pores 2-6-7-1), the new species is similar to the following congeners of the North Pacific: C. zachirus Kido , C. cyclocephalus , С. longifilis Garman , С. melanuroi-des Schmidt ( Garman 1892; Schmidt 1950; Kido 1983, 1985). Careproctus laperousei differs from C. zachirus and C. сyclocephalus in having a black peritoneum (pale in the both) and shorter head (22.5 % SL vs. 25.7–29.9 and 25.7–27.7 % SL). The new species differs from С. longifilis and С. melanuroides by larger disk (37 % lc vs. 16–22 and 25–26 % lc).

Careproctus laperousei differs from the recently described C. shigemii Matsuzaki, Mori, Kamiunten, Yanagimoto and Kai from off Rausu, Shiretoko Peninsula, Hokkaido, depth 200–300 m ( Matsuzaki et al. 2020) by cephalic pores pattern (2-6-6- 1 in the latter), fewer pectoral-fin rays (26 vs. 29–31) and black peritoneum (pale in C. shigemii ).

Figures

FIGURE 1. Careproctus laperousei sp. nov., holotype, ZMH 26369: A–C, fresh specimen; D–E, preserved specimen.

FIGURE 2. Fragment of a radiograph, holotype of Careproctus laperousei sp. nov., ZMH 26369: r—two pairs of pleural ribs on the vertebrae 8 and 9, h—haemal arch of the first caudal vertebrae.

FIGURE 3. Osteodiscus andriashevi, 166 mm TL, 151 mm SL, ZIN 49360, Sea of Okhotsk: A, lateral view, B, ventral view.