Bathylagichthys kobylianskyi Gon & Stewart

Gon, Ofer & Stewart, Andrew L., 2014, A new species of the genus Bathylagichthys (Pisces, Bathylagidae) from New Zealand, Zootaxa 3884 (4), pp. 371-378 : 373-377

Bathylagichthys kobylianskyi Gon & Stewart , new species

Figure 2 a–c; Table 1

Bathylagichthys problematicus: Kobyliansky 1990: 27 , in key.

Holotype. NMNZ P. 35456, 129.8 mm SL, New Zealand, Hikurangi Trench, 42°12’S, 177°30’E, plankton trawl, 20–60 m, RV Tangaroa, TAN 9802/188, February 1998.

Paratypes. New Zealand EEZ: NMNZ 13911, 142.7 mm, North Island, East Cape Ridge to southern Kermadec Trench, 37°50.9’S, 178°55.4’E, midwater trawl, 30 m, RV James Cook, JCO 7913/004, 30 September 1979; NMNZ P.13912, 53.4 mm, North Island, off Mahia Peninsula, outer Hikurangi Trench, 39°9.51’S, 179°10.7’E, midwater trawl, 30 m over 1700 m, RV James Cook, JCO 7913/031, 3 October 1979; NMNZ 13914, 125 mm, North Island, SE of Gisborne, western Hikurangi Trench, 39°5.07'S, 178°37.685'E, midwater trawl, 30 m, RV James Cook, JCO 7913/020, 1 October 1979; NMNZ P.13915, 2: 60–132 mm, North Island, E of East Cape Ridge, 38°22.16'S, 179°15.69'E, midwater trawl, 30 m, RV James Cook, JCO 7913/010, 1 October 1979; NMNZ P.13916, 2: 126.7–148.3 mm, North Island, Gisborne, Ranfurly Bank, 38°22.0’S, 179°45.9'E, midwater trawl, 30 m, RV James Cook, JCO 7913/012, 10 October 1979; NMNZ P.17971, 3: 50–145 mm, North Island, East Cape Ridge, 38°22'S, 179°35.35'E, midwater trawl, 30 m, RV James Cook, JCO 7913/011, 1 October 1979; NMNZ P.17992, 5: 49–174 mm, North Island, E of Mahia Peninsula, 39°0.64'S, 178°26.065'E, midwater trawl, 30 m over 1871– 1414 m, RV James Cook, JCO 7913/021, 1 October 1979; NMNZ P.19969, 89.1 mm, North Island, Gisborne, SE of East Cape, 37°51.65'S, 178°55.7'E, midwater trawl, 30 m, RV James Cook, JCO 8001/017, 11 January 1980; NMNZ P. 20680, 103.15 mm, North Island, East Cape sampling area, fine mesh midwater trawl, RV James Cook, JCO 8109/201, June 1981; NMNZ P. 35414, 103 mm, Hikurangi Trench, 40°05.0’S, 179°20.0’E, 20–60 m, RV Tangaroa, TAN 9802/0133, February, 1998; NMNZ P. 39740, 120 mm, Southern New Caledonian Basin, 35º59.02'S, 170º03.58'E, midwater trawl, 0–1975 m, RV Tangaroa, NORFANZ TAN 0308/168, 5 June 2003; NMNZ P. 53051, 103.5 mm, Hikurangi Trench, 40°08.46’S, 178°14.59’E, midwater trawl, 15–98 m, RV Tangaroa, TAN 9503/056, 29 March, 1995; NMNZ P. 54489, 149.7 mm, North Island, Hawke’s Bay, N of Mahia Peninsula, 39°09.95’S, 178°48.76’E, midwater trawl, 90–120 m, RV James Cook, JCO 7913/028, 2 October 1979; NMNZ P.56083, 85.9 mm, collected with holotype; BMNH 2014.7.21.2–3, 2: 55.95–119.5 mm (originally part of NMNZ P.13912); CSIRO H 7584-01, 2: 113.6–137.1 mm (originally part of NMNZ P.13911); SAIAB 200132, 3: 116.7–145.7 mm (originally part of NMNZ P.13916). Norfolk Ridge: NMNZ P.18546, 2: 54–140 mm, E of Wanganella Bank, 32°14.35'S, 167°47.8'E, midwater trawl, 125 m over 1640–1678 m, RV James Cook, JCO 8516/ 0 21, 24 October 1985. Tasman Sea: NMNZ P.18917, 3: 124.6–154.5 mm, northern central Tasman Basin, 40°06.95'S, 160°15.75'E, midwater trawl, 35–45 m, RV James Cook, JCO 8516/008, 16 October 1985; MCZ 171511, 152.7 mm, NSMT-P 120864, 2: 138.8–152.4 mm and USNM 432150, 3: 124.4–131.4 mm (all three lots originally part of NMNZ P.18917).

Comparative material. Bathylagichthys greyae – Western North Atlantic: FMNH 49730, holotype, 71.0 mm; CAS (SU) 50974, paratype, 35.5 mm; MCZ 162109, 75 mm; MCZ 164742, 105 mm. Gulf of Mexico: MCZ 91362, 2: 68.8–78.8 mm. Middle North Atlantic: MCZ 91357, 64 mm; MCZ 149497, 141 mm; MCZ 159262, 136 mm; MCZ 159263, 11: 72–122 mm. Eastern North Atlantic: MCZ 66131, 84 mm; MCZ 150908, 59 mm; MCZ 150970, 2: 79–92 mm; MCZ 159259, 2: 57–61 mm; SAIAB 54811, 2: 127.0– 127.4 mm; SAIAB 54813, 131.9 mm; SAIAB 54815, 3: 112.4–142.5 mm; all radiographs, except SAIAB material. Bathylagichthys problematicus — Namibia: SW of Luderitz, IIPB 708–1981, 288 mm; IIPB 709–1981, 185 mm; IIPB 710–1981, 220 mm, all paratypes collected with the holotype; IIPB 114–1985, 2: 226.0– 231.2 mm.

Diagnosis. A species of Bathylagichthys with two branchiostegal rays, 43–45 (usually 44) vertebrae ( Fig. 2 b), 25–31 (usually 27–31) gill rakers, short supraorbital bone not reaching posteriorly over centre of eye ( Fig. 3 ), and caudal peduncle about as long as deep and of similar length to anal-fin base.

Description. Data in parentheses are the range for paratypes. Dorsal-fin rays 13 (12–14); anal-fin rays 11(10–13); pectoral-fin rays 11 (10–12); pelvic-fin rays 10 (9–12); branchiostegal rays 2, in all; gill rakers 9 + 20 (8–10 + 17–21); pyloric caeca 11 (9–14); vertebrae 44 (43–45). Body elongate, sub-cylindrical anteriorly, becoming strongly compressed on caudal peduncle; body depth gradually increasing from 8.0 (6.8–8.8) at preopercle edge to 6.7 (5.95–7.1) at pectoral-fin base, reaching its deepest point, 5.6 (5.0–6.3), at dorsal-fin origin; it then gradually tapers posteriorly to 5.6 (6.2–7.6) at pelvic-fin insertion and 7.75 (7.5–8.95) at anal-fin origin, reaching its narrowest point at caudal peduncle 10.9 (9.9–11.9), all in SL. Body width 1.5 (1.3–2.0) in its depth at pectoral-fin base. Head moderate, its length 4.4 (3.6–4.9) in SL. Snout 1.3 (1.2–1.6) in eye diameter and 4.2 (3.8–5.0) in head length; eye large, its diameter 3.2 (2.8–3.5), upper jaw 4.3 (4.0–5.8) and lower jaw 3.6 (3.4–4.5), all in head length. Supraorbital bone short not reaching vertical at centre of eye ( Fig. 3 ), 1.6 (1.6–2.0) in eye diameter. Caudal peduncle about as deep as long, its least depth 0.92 (0.9–1.2) in its length, and its length 11.9 (8.9–12.2) in SL, and 1.0 (0.9–1.3) in anal-fin base. Dorsal fin origin at or slightly in front of middle of body (as the standard length), distance from snout to dorsal-fin origin 2.2 (2.0–2.2) in SL. Pectoral fin inserted low on body, distance from upper pectoral-fin base to dorsal midline of body 1.3 (1.1–1.3) in body depth at pectoral-fin base. Adipose fin with short base, its origin over anterior half of anal-fin base, and its distance from snout 1.5 (1.1–1.2) in SL. Distance from snout to anal-fin origin 1.2 (1.2–1.3) and to upper pectoral-fin base 4.1 (3.5–4.7) in SL. Pelvic-fin inserted below end of dorsal-fin base, its distance from snout 1.7 (1.7–1.9) in SL. Distance from upper pectoral-fin base to pelvic-fin insertion 2.9 (2.8–3.7) in SL; distance from pelvic-fin insertion to anal-fin origin 3.75 (3.55–4.6) in SL and 1.3 (1.1–1.4) in distance from upper pectoral-fin base to pelvic-fin insertion; distance from dorsal-fin origin to adipose fin 2.4 (2.4–2.8) in SL. Mouth small, upper jaw ends at or before anterior edge of eye and has no teeth. Lower jaw with single series of small close-set multi-cuspid teeth (sometimes damaged or abraded). Vomerine teeth small, slender, with slightly incurved tip, in single series and separated from each other by a distinct gap of about one tooth width.

Holotype Paratype Paratype Paratype Paratype Colour when fresh (without scales and skin partially lost), pale brown, darker dorsally, peppered with dark brown dots of various sizes ( Fig. 2 c); snout, jaws, interorbital space, temporal area and opercle blackish; black peritoneum shown through ventral body wall between pectoral and pelvic fins, becoming brownish and narrower between pelvic and anal fins. Dorsal and caudal fins blackish; pectoral, pelvic and anal fins pale; adipose fin blackish at base, dusky distally, with pale tip.

Colour in alcohol: body brown, darker above lateral line, and covered with dark brown dots of various sizes; tip of snout and opercle dark brown, cheek paler; fins dusky, caudal fin darkest; adipose fin with minute dark dots on its proximal part.

Dorsal-fin rays Anal-fin rays

10 11 12 13 14 n 9 10 11 12 13 n Bathylagichthys greyae 8 16 3 27 10 6 16 B. kobylianskyi 2 27 13 42 1 10 21 11 43 B. problematicus 4 1 5 1 2 2 5 Total gill rakers

24 25 26 27 28 29 30 31 32 33 34 35 n Bathylagichthys greyae 2 4 1 7 B. kobylianskyi 1 5 10 8 4 4 32 B. problematicus 1 2 1 1 5 Distribution. This species is presently known from the New Zealand EEZ, Norfolk Ridge and Tasman Sea. Most specimens were collected in the vicinity of East Cape, North Island. The southernmost capture was on the northern Chatham Rise slope (NMNZ P.35456) and the northernmost capture was on the Norfolk Ridge, just outside the New Zealand EEZ (NMNZ P.18546). One lot of specimens (NMNZ P.18917) was collected in the northern central Tasman Basin, well outside the New Zealand EEZ. Specimens of this species were usually trawled at relatively shallow depths of 15–320 m over a bottom depth range of 800–4700 m.

Etymology. Bathylagichthys kobylianskyi is named for Dr Stanislav Kobyliansky of the P.P. Shirshov Institute of Oceanology, Moscow, in recognition of his contribution to the systematics of the family Bathylagidae .

Total vertebrae

42 43 44 45 46 47 48 49 50 51 n Bathylagichthys greyae 8 18 3 29 B. kobylianskyi 3 39 3 45 B. problematicus 1 1 3 5 Comparisons. Bathylagichthys kobylianskyi is closely related to B. greyae ( Cohen, 1958) as both species have two branchiostegal rays; the remaining species of this genus have three or four branchiostegal rays ( Kobyliansky, 1990). They also share a short supraorbital not reaching a vertical through the middle of the eye, a short caudal peduncle of about the same length as anal-fin base, and a similar count of dorsal-fin rays ( Table 2). However, B. greyae differs from B. kobylianskyi in having modally more anal-fin rays and vertebrae ( Tables 2 & 4), and fewer gill rakers ( Table 3; Carter & Hartel, 2002), as well as a shallower body showing lower percentage SL values at every point at which body depth was measured ( Table 5).

Remarks. The pectoral-fin was not damaged in four specimens in which its length was 4.4–6.4 in SL (15.5–22.9% SL). The pelvic fin was intact in two specimens in which its length was 6.5–7.3 in SL (13.7–15.3% SL). The bathylagid fishes collected during the surveys of the New Zealand EEZ included a number of specimens with two branchiostegal rays and 43–45 vertebrae that identified as Bathylagichthys problematicus using Kobyliansky’s (1990) key for this genus. Examination of X-rays of the three extant paratypes of B. problematcius revealed 50–51 vertebrae ( Fig. 2 d) and, as a consequence, that the New Zealand specimens, having a lower vertebral count, represent another species. In an earlier paper Kobyliansky (1985) reported B. greyae from 16 specimens collected in the cold temperate waters of the southern hemisphere. He later re-identified some of these specimens as a new species he named B. australis ( Kobyliansky, 1990) , presumably leaving the remainder as B. greyae . Although Kobyliansky’s (1990) key separates B. greyae from “ B. problematicus ” unambiguously, we compared our material with North Atlantic specimens of the former species, including data obtained from X-rays of its holotype and one paratype ( Tables 2–5). The differences we observed (see Comparsions above) convinced us that “ B. problematicus ” of Kobylianski (1990) is an undescribed species. We anticipate that this species will be found elsewhere in the southern hemisphere.

B. kobylianskyi B. greyae

(16: 85.9–149.7 mm) (6: 112.4–142.5 mm)

Body depth @ preopercle 11.3–14.75 10.2–11.5

Body depth @ Pectoral-fin base 14.0–16.8 11.0–13.9

Body depth @ dorsal-fin origin 16.0–19.9 12.25–15.7

Body depth @ pelvic-fin insertion 13.1–16.0 10.6–13.3

Body depth @ anal-fin origin 11.2–13.35 9.75–11.45

Least depth of caudal peduncle 8.4–10.1 7.2–8.7

Figures

FIGURE 2. (a) Bathylagichthys kobylianskyi NMNZ P. 35456, holotype, 129.8 mm, preserved (O. Gon). (b) Radiograph of the holotype (M. Lisher). (c) B. kobylianskyi NMNZ P. 39740, paratype, 120 mm, after death (NORFANZ Founding Parties / C. Struther). (d) Radiograph of B. problematicus IIPB 709 / 1981, paratype (M. Lisher).

FIGURE 3. Dorso-lateral view of the right supraorbital of Bathylagichthys kobylianskyi NMNZ P. 20680, paratype. Arrows point to anterior and posterior ends of the bone.

Tables

TABLE 1. Proportional measurements of selected type specimens of Bathylagichthys kobylianskyi expressed as percentage of the standard length.

Standard length (mm)	NMNZ P.35456 129.8	BMNH NMNZ 2014.7.21.2-3 P. 56083 55.95 85.9	NMNZ P.20680 103.15	BMNH 2014.7.21.2-3 119.5
Head length (mm)	29.4	15.5 22.7	25.85	28.4
Body depth @ preopercle Body depth @ Pectoral-fin base	12.5 15.0	14.75 13.8 16.8 14.4	13.0 16.2	13.4 15.4
Body depth @ dorsal-fin origin	18.0	17.9 16.1	18.0	18.6
Body depth @ pelvic-fin insertion Body depth @ anal-fin origin	15.7 12.9	14.3 13.4 11.2 11.7	14.4 12.55	15.8 12.85
Length of head	22.65	27.7 26.4	25.1	23.8
Length of snout Eye diameter	5.35 7.1	7.1 6.4 10.0 8.7	5.8 7.8	5.9 7.6
Length of upper jaw	5.3	6.9 5.9	5.2	6.3
Length of lower jaw Length of dorsal-fin base	6.3 14.3	7.6 7.3 13.05 11.7	6.6 14.6	6.95 13.5
Length of anal-fin base	8.7	11.4 9.95	10.3	10.5
Depth of caudal peduncle Length of caudal peduncle	9.2 8.4	9.3 9.55 8.6 9.4	9.6 9.9	9.4 9.2
Snout to dorsal-fin origin	46.1	50.0 46.9	45.8	48.3
Snout to adipose fin Snout to anal-fin origin	85.2 83.2	84.9 84.3 81.05 80.9	83.7 79.8	88.1 85.9
Snout to upper pectoral-fin base	24.4	28.2 27.1	27.0	25.3
Snout to pelvic-fin insertion End of dorsal-fin base to adipose fin	57.9 25.35	56.0 57.7 23.8 25.8	55.9 25.55	58.6 28.6
Upper pectoral-fin base to pelvic-fin insertion	34.2	28.9 29.5	29.5	35.9
Pelvic-fin insertion to anal-fin origin Greatest body width	26.7 9.9	24.8 23.5 9.2 10.8	25.0 10.0	28.2 10.25
Upper pectoral-fin base to dorsal midline of body	11.6	13.6 12.05	13.2	12.3
Length of supraorbital bone Dorsal-fin origin to adipose fin	4.4 41.4	5.45 4.9 36.6 37.8	4.8 40.0	4.4 41.7