Abyssobrotula hadropercularis, Ohashi, Shinpei & Nielsen, Jørgen G., 2016

Ohashi, Shinpei & Nielsen, Jørgen G., 2016, A new species of Abyssobrotula (Ophidiiformes, Ophidiidae) from the Kuril-Kamchatka Trench, Zootaxa 4132 (4), pp. 559-566 : 560-564

Abyssobrotula hadropercularis sp. nov.

( Figs. 1–6 , Table 1)

Holotype. NSMT-P 121429, 200 mm SL, female, Kuril-Kamchatka Trench (46°55.53′N, 160°2.84′E – 46°54.14′N, 160°1.99′E), R/V Hakuho-maru, st. NBD-2, beam trawl, 5204–5205 m, 31 May 2014.

Paratype. NSMT-P 121428, 149 mm SL, male, Kuril-Kamchatka Trench (47°0.22′N, 160°2.62′E – 47°0.91′N, 160°1.29′E), R/V Hakuho-maru, st. NBD-1, beam trawl, 5179–5223 m, 27 May 2014.

Diagnosis and similarity. Abyssobrotula hadropercularis differs from A. galatheae , the only other species of the genus, by the following characters ( A. galatheae mentioned in parenthesis): Opercular spine pointed and strong (vs. flat and weak), pectoral fin rays 14–15 (vs. 10–11), head length 22.0–22.5 % SL (vs. 17.5–19.5), diameter of pigmented eye 1.2–1.3 % SL (vs. 0.7–0.9), preanal length 42.5 % SL (vs. 33.0–41.5), prepelvic length 14.0–14.5 % SL (vs. 10.5–12.5), rakers on anterior gill arch robust and close-set (vs. thin and well separated).

Description. Selected meristic and morphometric characters are shown in Table 1. The description is based on the holotype, differences observed in the paratype mentioned in parenthesis. Body compressed with tapering tail, depth at anus about 7 times in SL. Head inflected downward, its length slightly less than half preanal-fin length. Cycloid scales in some parts of head and body ( Fig. 2 ), but empty scale pockets indicate that most areas of body and head covered with scales. Judging from the loose skin, snout and dorsal part of head seem to have been swollen. Two pairs of nostrils with wide opening between tip of snout and eye: Anterior nostril circular at tip of snout and posterior nostril between anterior nostril and eye, slightly exposing lateral ethmoid. Eye small, 3.8 (4.6) times in snout length. Mouth inferior, upper jaw long, posterior margin extending well behind eye. Supramaxilla elliptical. Opercle robust, but its dorsal margin extremely thin making rudimentary bulge above spine; its spine pointed and strong not reaching posterior end of subopercle. Preopercle thin and soft, its hind margin without spines. Gill opening wide. Anterior left gill arch (right gill arch is missing in holotype) with 5 (4–5) short rakers on upper branch, one long raker at the angle between branches, and lower branch with 7 (8–9) long rakers followed by 7 (7–8) short rakers. Long rakers robust and close-set ( Fig. 3 ). Longest gill raker on anterior arch about three times length of longest gill filament. Pseudobranch consisting of two short filaments. Branchiostegal rays 7 in left and 8 in right (8 in both sides). Lateral line indistinct. Base of dorsal and anal fins long, continuous with caudal fin; their rays unbranched. Origin of dorsal fin above base of pectoral fin. Origin of anal fin well anterior to midpoint of body. Pectoral fin slender extending beyond anus. Pelvic-fin rays thread-like, originating below preopercle. Caudal fin missing most parts of rays (with slender rays). Anus just anterior to anal-fin origin.

A. hadropercularis sp. nov. A. galatheae *

NSMT-P 121429 NSMT-P 121428

Holotype Paratype Min (mean) max No SL (mm) 200 149 67–157 16 Meristic characters

Dorsal-fin rays 116 112 97 (105.1) 116 15 Caudal-fin rays 8 8 8 16 Anal-fin rays 90 87 76 (83.0) 96 15 Pectoral-fin rays 14 (left), 15 (right) 14 (left), 15 (right) 10 (10.1) 11 16 Pelvic-fin rays 2 2 2 16 Precaudal vertebrae 19 20 17 (18.3) 19 16 Caudal vertebrae 48 48 49 (51.5) 56 16 Dorsal-fin origin above vertebra number 8 9 6 (7.1) 8 15 Dorsal-fin origin above anal-fin ray number 28 27 23 (25.8) 30 15 Anal-fin origin below vertebra number 23 24 21 (21.5) 23 15 Long gill rakers 8 9 8 (9.9) 11 16 Total gill rakers 20 21 15 (18.6) 22 16 Morphometric characters in % SL

Head 22.5 22.0 17.5 (18.4) 19.5 13 Depth at origin of anal fin 14.0 13.5 11.0 (13.7) 15.0 11 Upper jaw 11.5 11.5 9.5 (10.5) 12.0 13 Diameter of pigmented eye 1.2 1.3 0.7 (0.8) 0.9 6 Postorbital 14.5 14.5 11.5 (12.4) 13.0 10 Prepelvic 14.5 14.0 10.5 (11.8) 12.5 13 Preanal 42.5 42.5 33.0 (38.3) 41.5 14 Predorsal 25.0 25.5 20.5 (21.9) 25.5 14 Pelvic fin to anal fin origin 28.5 29.5 25.0 (27.3) 29.0 12 Pectoral fin** 24.0 23.0 21.0–51.0 13 Pelvic fin** 12.5 13.0 4.6–12.0 10 Long gill raker 3.3 3.4 2.6 (3.3) 3.8 8 Longest gill filament 1.1 1.2 0.4 (0.6) 0.8 6 * 14 specimens from Nielsen (1977) and 2 specimens newly examined (NSMT-P 18975 and 98870)

**fin rays often broken

Head pores ( Fig. 4 ). Infraorbital pores 6, preoperculomandibular pores 7 (left) or 8 (right) (8). Anterior five preoperculomandibular pores of on ventral surface of lower jaw.

Dentition. Premaxilla and dentary with 2–7 irregular rows of small, pointed teeth. Palatines with several irregular rows of small, pointed teeth. Vomer boomerang-shaped with 2–5 (2–3) irregular rows of small, pointed teeth (inner row regular). Two median and one sideways on basibranchials in holotype, most probably caused by the partly destroyed mouth-floor (fig. 5 showing undisturbed basibranchial tooth patches of paratype).

Axial skeleton (based on radiographs). First neural spine about half length of second. Neural spines 2–7 gradually decreasing in length and the posterior seven precaudal spines increasing in length. Bases of neural spines 4–19 (20) enlarged. Parapophyses developed on vertebrae 7–19 (20). Pleural ribs on vertebrae 3–17 (18). Epipleural ribs could not observed.

Otolith ( Fig. 6 ). Otolith small (0.8 mm long) nearly round in outline except for slightly elevated mid-dorsal region. Inner face almost flat, smooth, with barely visible, shallow, centrally placed sulcus. Outer face strongly convex, smooth. Otolith length to height = 1.2, length to thickness = 1.8, and length to sulcus = 3.3.

Colour (nine months after captured). Oral cavity and dorsal area and sides of head bluish and lower part dark brown. Eyes bluish with light lens. Branchial cavity and peritoneum dark brown. Abdomen dark bluish. Sides of body light brown. Fin rays with dark brown pigmentation.

Distribution. Known from two abyssal (5179–5223 meters) locations in the Kuril-Kamchatka Trench, Western North Pacific Ocean.

Etymology. The specific name, hadropercularis , derives from hadros (bulky) and opercularis (gill cover) in reference to the robust opercle.

Comparative material. Abyssobrotula galatheae , 16 specimens: ZMUC P77599, holotype, 130 mm SL, female, Kermadec Trench (36°07′S, 178°32′W), 5230–5340 m, R/V Galathea , 23 Feb. 1952; ZMUC P77600, paratype, 123 mm SL, female, Kermadec Trench (32°10′S, 175°54′W), 5850–5900 m, R/V Galathea , 18 Feb. 1952; ZMUC P77601–77602, paratypes, 100–110 mm SL, female, Kermadec Trench (36°34′S, 178°57′W), 4540 m, R/V Galathea , 24 Feb. 1952; CAS 36574, 133 mm SL, female, Eastern Pacific (1°19′N, 84°07′W – 1°12′N, 83°56′W), 2926–3292 m, R/V Te Vega, 6 Oct. 1968; MNHN 1976-43 and 1976-44, 67 and 132 mm SL, sex unknown and female, Eastern South Atlantic (18°52.1′S, 7°23.1′E), 5048 m, R/V Jean Charcot, 6 June 1971; MNHN 1976-45, 156 mm SL, female, Eastern Atlantic (0°23.2′N, 3°42.4′W), 4975 m, R/V Jean Charcot, 28 May 1971; NSMT-P 18975, 111 mm SL, female, Izu-Bonin Trench (30°41.3′N, 141°49.7′E), 4610 m, R/V Soyo-maru, 23 Nov. 1974; NSMT-P 98870, Western North Pacific (31°43.4′N, 158°05.3′E – 31°39.0′N, 158°07.1′E), 2171– 2491 m, R/V Kaiyo-maru, 31 May 1984; UMML 29070, 140 mm SL, female, Puerto Rico Trench (19°43′N, 67°05′W), 8370 m, R/V Pillsbury, 21 Jan. 1970; USNM 226588, 142 mm SL, Western Atlantic (28°43′N, 78°49′W), 5105 m, R/V Columbus Iselin, 12 Feb. 1978; ZIL 43250, 125 mm SL, sex unknown, Eastern Indian Ocean (15°41′S, 104°57′E), 5750–5940 m, R/V Vitiaz, 26 Nov. 1959; ZMUC P77676, 75 mm SL, sex unknown, Western North Atlantic (38°39.5′N, 69°58.1′W – 38°37.8′N, 70°01′W), 3111–3115 m, R/V Chain, 11 July 1975; ZMUC P77685–77687, 142– 157 mm SL, females, Eastern Pacific (9°23′N, 89°32′W), 3570 m, R/V Galathea , 6 May 1952.

Figures

FIGURE 1. Holotype of Abyssobrotula hadropercularis sp. nov., NSMT-P 121429, female, 200 mm SL, Kuril-Kamchatka Trench, 5204 – 5205 m. Scale bar indicates 20 mm.

FIGURE 2. SEM image of scale from cheek (left) and above pectoral fin (right) of Abyssobrotula hadropercularis, NSMT-P 121428, paratype, male, 149 mm SL. Scale bar indicates 1 mm.

FIGURE 3. Anterior, right gill arch from two Abyssobrotula species: (A) A. hadropercularis, paratype, NSMT-P 121428, 149 mm SL; (B) A. galatheae, ZMUC P 77686, 142 mm SL. Scale bars indicate 5 mm.

FIGURE 4. Head and anterior part of body of holotype of Abyssobrotula hadropercularis, NSMT-P 121429. Arrows indicate infraorbital pores hidden by loose skin. Scale bar indicates 10 mm.

FIGURE 5. Basibranchial tooth patches from paratype of Abyssobrotula hadropercularis, NSMT-P 121428. Scale bar indicates 2 mm.

FIGURE 6. Right sagittal otolith from (A) holotype of Abyssobrotula hadropercularis, NSMT-P 121428 and from (B) A. galatheae, USNM 226588, (a) inner view, (b) ventral view, (c) anterior view (illustrated by Werner Schwarzhans). Scale bars indicate 1 mm.