Macrourus whitsoni Regan 1913

Macrourus whitsoni (Regan 1913)

Chalinura whitsoni Regan, 1913: 236, Pl. 2 [fig. 2]. 2 syntypes: 1—BMNH 1912.7.1.87, off Coats Land, Antarctica, 71°22' S, 16°34' W, 1410 fathoms [2578 m]; 2—NMSZ 1921.143.357 South Atlantic Ocean, 48°06' S, 10°05' W, depth 1742 fathoms [3186 m.]

Macrourus whitsoni — Trunov & Konstantinov, 1989 (probably includes some M. caml, description, compared with M. carinatus, in Russian, English summary). Trunov & Konstantinov, 1990: 44–54 (described, illustrated, key, in Russian, English summary). Iwamoto in Cohen et al., 1990: 233–240 (described, illustrated, key). Iwamoto in Gon & Heemstra, 1990: 192, 202–206 (described, illustrated, key).

Diagnosis. Ventral surface of the head mostly scaled, except for scaleless areas anterior to the mouth and on the anterior third of the lower jaw. Pelvic fin with 9 (rarely 10) rays. Lower jaw with a single row (sometimes 2 rows at tip) of long, slender, spaced (about a tooth-length) teeth. Upper jaw with 3–5 rows of teeth with teeth in the outer row enlarged relative to those of inner rows. Body scales relatively small, 36–45 in a diagonal row from anal fin origin to lateral line. Pyloric caeca 15–26.

Specimens examined. Syntype. BMNH 1912.7.1.87 (63 mm HL, 274 mm TL), off Coats Land, 71º 22' S, 16º 34' W, 1410 fathoms (2578 m) Scotia stn. 417, trawl, 18 Mar 1904, here designated as the lectotype. The second syntype, NMSZ 1921.143.357 (see Herman et al., 1990), (approx. 420 mm TL) South Atlantic Ocean, 48º 6' S, 10º 5' W, 1742 fathoms (3186 m) was unavailable for study.

Non-type specimens (45). NMNZ P.036149 (109 mm HL, 470 mm TL), Ross Sea slope, 77º 20' S, 169º 25' E, 780–848 m, FV San Aotea II, OBS 1180/028, bottom longline, 22 Jan 1999; NMNZ P.036150 (2, 133– 137 mm HL, 642–654 mm TL), Ross Sea slope, 73º 12' S, 177º 6' W, 978–1305 m, FV Janas, OBS 1181/028, bottom longline, 19 Jan 1999; NMNZ P.037582 (3, 93– 107 mm HL, 353–442 mm TL), Ross Sea slope, 72º 39' S, 179º 35' W, 76–2, 793 m, FV Sonrisa, OBS 1311/001, bottom longline, 30 Jan 2000; NMNZ P.037797 (2, 97– 109 mm HL, 435–517 mm TL), Ross Sea slope, 70º 55' S, 179º 13' E, 1217–1365 m, FV San Aotea II, OBS 1430/123, bottom longline, 25 Feb 2001; NMNZ P.037807 (2, 95– 109 mm HL, 396–423 mm TL), Ross Sea slope, 71º 28' S, 178º 10' W, FV Sonrisa, OBS 1431/10/R5C, bottom longline, 28 Jan 2001; NMNZ P.038565 (100 mm HL, 456 mm TL), Scott Island, Ross Sea, 66º 29' S, 176º 30' W, 1179–1212 m, FV San Aotea II, OBS 1595B/150A, bottom longline, 23 Apr 2002; NMNZ P.038619 (88 mm HL, 412 mm TL), Ross Sea slope, 75º 12' S, 174º 6' W, 1323–1368 m, FV Janas, OBS 1593A/060, bottom longline, 0 6 Feb 2002; NMNZ P.039868 (79 mm HL, 338 mm TL), Balleny Islands, 67º 42' S, 167º 9' E, 1307–1340 m, FV San Liberatore, OBS 1743/031, bottom longline, 10 Mar 2003; NMNZ P.039984 (79 mm HL, 338 mm TL), Pacific– Antarctic Ridge, 65º 15' S, 178º 10' W, 1445–1452 m, FV Janas, OBS 1728/077, bottom longline, 16 Feb 2003; NMNZ P.039985 (81 mm HL, 256 mm TL), Pacific– Antarctic Ridge, 66º 40' S, 177º 26' W, 1160–1339 m, FV Janas, OBS 1728/020, bottom longline, 0 8 Jan 2003; NMNZ P.039986 (74 mm HL, 330 mm TL), Pacific– Antarctic Ridge, 65º 25' S, 178º 18' W, FV Janas, OBS 1728/084, bottom longline, 20 Feb 2003; NMNZ P. 040622 (92 mm HL, 435 mm TL), Scott Canyon, Ross Sea, 72º 13' S, 175º 55' E, 1333–1382 m, FV Gudni Olafsson, OBS 1843/034, bottom longline, 20 Jan 2004; NMNZ P. 040623 (82 mm HL, 371 mm TL), Adare Seamounts, Ross Sea, 71º 27' S, 176º 47' E, 1200–1221 m, FV Gudni Olafsson, OBS 1843/042, bottom longline, 25 Jan 2004; NMNZ P. 041442 (149 mm HL, 657 mm TL), Ross Sea slope, 71º 20' S, 179º 18' W, 1315–1679 m, FV San Aspiring, OBS 2011/058, bottom longline, 23 Jan 2005; NMNZ P. 042295 (2, 115– 119 mm HL, 525–530 mm TL), NMNZ P. 042316 (2, 117– 122 mm HL, 542–588 mm TL) Off Wilkes Land, 64º 22' S, 114º 23' E, 1696–1738 m, FV San Aspiring, OBS 2183/093, bottom longline, 15 Feb 2006; NMNZ P.043665 (109 mm HL, 512 mm TL), Ross Sea slope, 72º 5' S, 175º 35' E, 1567–1587 m, RV Tangaroa, IPY/ CAML TAN 0802/133, bottom trawl, 22 Feb 2008; 43732 (125 mm HL, 592 mm TL), NMNZ P.043733 (118 mm HL, 545mm TL), NMNZ P.043734 (113 mm HL, 573 mm TL), NMNZ P.043735 (131 mm HL, 607 mm TL), NMNZ P.043736 (106 mm HL, 500 mm TL), NMNZ P.043737 (10, 46– 73 mm HL, 204–334 mm TL) Ross Sea slope, 71º 52' S, 174º 4' E, 1954–1990 m, RV Tangaroa, IPY/ CAML TAN 0802/167, bottom trawl, 25 Feb 2008; NMNZ P.043855 (67 mm HL, 281 mm TL), North Scott Seamounts, 68º 7' S, 179º 15' W, 855–879 m, RV Tangaroa, IPY/ CAML TAN 0802/211, bottom trawl, 0 3 Mar 2008; NMNZ P. 051973 (90 mm HL, 387 mm TL), Ross Sea slope, 69º 21' S, 178º 39' W, 425–1661 m, FV Janas, OBS 1429/122, bottom longline, 20 Feb 2001; NMNZ P. 051974 (104 mm HL, 452 mm TL), NMNZ P. 051975 (2, 115– 124 mm HL, 520–546 mm TL) Cosmonaut Sea, 66º 19' S, 33º 14' E, 1317–1334 m, FV Janas, OBS 2068/033, bottom longline, 26 Mar 2005; NMNZ P. 051987 (125 mm HL, 578 mm TL), Ross Sea slope, 73º 15' S, 177º 18 ' W, 940–1211 m, FV Janas, OBS 1181/027, bottom longline, 19 Jan 1999.

Counts and measurements (Tables 1 –2).

Description (Figures 10–11, Tables 1 –2). Head large, length 3.2 to 5.1 into total length. Small scutes on head ridges, armed with short spinules. Slightly pointed snout, length less than orbit diameter, tipped with a prominent scute. Upper jaw larger than orbit diameter, posterior end of premaxilla below about rear of orbit. Chin barbel about one third of orbit diameter.

Teeth in both jaws pointed, may be slightly curved inwards. Upper jaw teeth in up to 4–5 rows at tip but 2 rows posteriorly with outer teeth noticeably enlarged. Lower jaw with long, slender, spaced (about a tooth–length) teeth in 1–2 rows at tip, usually 1 row posteriorly.

Origins of pectoral and pelvic fins about on same vertical, and both slightly in advance of origin of first dorsal fin. Pelvic fin relatively long compared to others in genus.

Body scales small, deciduous. Those between lateral line and first dorsal fin base with a central row of small spinules and there may be one short row of small spinules on each side. Body scales on lower body lack a central spinule row. Dorsal head covered with small, flat, adherent scales, except for scaleless area around nostrils extending dorsally to nasal ridge but usually a few scales ventrally above suborbital ridge. Ventral surface of head anterior to mouth scaleless. Numerous rows of small flat scales lacking spinules at posterior end of ventral surface of head. Scales extending forward to about level with nostrils and reducing to a few rows anteriorly. Small scales on rear half to two–thirds of lower jaw.

Fresh colour of head and body pale to medium brownish, pale in smaller specimens. Sides of head and abdomen may be silvery to whitish under the scales. Lining of mouth, gill cavity, and lips greyish–black. Ventral surface of head brownish with numerous pale pore openings. Fins pale greyish–brown. Preserved specimens brownish overall.

Size. To about 660 mm TL. This appears to be the smallest species in the genus.

Distribution (Figure 5 D). Probably widespread in the Southern Ocean. Specimens examined in this study were from 64–77° S from the South Atlantic Ocean off Coats Land, south Indian Ocean (Cosmonaut Sea, Durmont D’Urville Sea), and South Pacific Ocean (Ross Sea, Balleny and Scott Islands slope, Pacific Antarctic Ridge), at 400–3200 m. The lectoype and paralectotype are the deepest records of the species (2579 and 3186 m respectively).

Comparisons and remarks (Table 3). Macrourus caml has 8 (rarely 7 or 9) pelvic fin rays, a band (2–3 rows) of small uniform-sized teeth in the lower jaw, lacks an outer row of enlarged teeth in the upper jaw, and 30–40 scales in a diagonal row from anal fin origin to lateral line. M. carinatus has large body scales with 19–25 in a diagonal row from anal fin origin to lateral line. Macrourus holotrachys (southern hemisphere) and M. berglax (northern hemisphere) both have an almost scaleless ventral surface of the head. See “Comparisons and remarks” for M. caml for comments about Trunov & Konstantinov (1989) work on M. whitsoni.

The paralectotype (NMSZ 1921.143.357) was unavailable for study and its identity is uncertain. In the description, Regan (1913) states that the pelvic fin is “9-rayed”, and that the macrourid genera included in the paper had “teeth in the lower jaw uniserial”. Both these characters suggest that the specimen is conspecific with the lectotype but doubt remains because the paralectotype is the northernmost (48º 6' S, Mid-Atlantic Ridge south of Gough Island) and deepest (3186 m) record compared to the specimens of Macrourus whitsoni examined in this study (Fig. 5 D).