Macrourus holotrachys Günther 1878

Mcmillan, Peter, Iwamoto, Tomio, Stewart, Andrew & Smith, Peter J, 2012, A new species of grenadier, genus Macrourus (Teleostei, Gadiformes, Macrouridae) from the southern hemisphere and a revision of the genus, Zootaxa 3165, pp. 1-24 : 15-16

Macrourus holotrachys Günther 1878

Macrurus holotrachys Günther, 1878: 24 . Holotype BMNH 1887.12.7.87, East of Rio de la Plata mouth, Challenger station 320, 600 fathoms [1097 m]. Günther, 1887: 136, Pl. 26 (redescribed, illustrated).

Macrourus holotrachys —Trunov, 1986: 22, 29–31 (described, in Russian, English summary). Trunov & Konstantinov, 1986: 125–135 (described, illustrated, 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 entirely or mostly scaleless but up to 8 small patches of scales (usually less than about 10 small scales per patch) may be present at the posterior end of head, beside articulation of lower jaw and beside posterior end of premaxilla, and rarely posteriorly on lower jaw. Pelvic fin with 8 or 9 rays (rarely 10). Lower jaw with 2–5 rows of small uniform-sized teeth reducing to 1 or 2 rows posteriorly. Upper jaw with 4–6 rows of small, uniform-sized teeth. Body scales large, thick, adherent, with a central row of strong spinules, 18–26 scales in a diagonal row from anal fin origin to lateral line. Pyloric caeca 9–16.

Specimens examined. Holotype. BMNH 1887.12.7.87 (50 mm HL, 220 mm TL), south east Atlantic Ocean east of Rio de la Plata, 37° 17' S, 53° 52' W, 600 fm (1097 m), Challenger stn. 320, 14 Feb 1876.

Non-type specimens (29, all taken by bottom longline). NMNZ P.036987 (143 mm HL, 640 mm TL), South Georgia, 54º 0' S, 39º 0' W, 1300–2000 m, Apr 1997; NMNZ P.038550 (153 mm HL, 681 mm TL), NMNZ P.038555 (185 mm HL, 802 mm TL), Pacific-Antarctic Ridge, 64º 6' S, 177º 20' E, 1508–1543 m, FV Jana s, Obs 1593b/226, 23 May 2002; NMNZ P.038556 (186 mm HL, 761+ mm TL), Pacific-Antarctic Ridge, 63º 16' S, 176º 7' E, 1195– 1404 m, FV San Aotea II, Obs 1595b/168b, 0 3 May 2002; NMNZ P.038572 (2, 150– 183 mm HL, 612–790 mm TL), Pacific-Antarctic Ridge, 63º 11' S, 174º 19' E, 1084–1224, FV San Aotea II, Obs 1595b/170A, 0 4 May 2002; NMNZ P.038573 (2, 132– 203 mm HL, 557–817+ mm TL), Pacific-Antarctic Ridge, 63º 16' S, 175º 5' E, 1368– 1383 m, FV San Aotea II, Obs 1595b/169A, 0 3 May 2002; NMNZ P.038598 (165 mm HL, 682 mm TL), Pacific- Antarctic Ridge, 63º 22' S, 175º 33' E, 1163–1166 m, FV Janas, Obs 1593b/228, 26 May 2002; NMNZ P.039922 (166 mm HL, 600+ mm TL), Pacific-Antarctic Ridge, 64º 34' S, 171º 11' W, 1278–1463 m, FV Avro Chieftain, Obs 1841/018, 14 Dec 2003; 39949 (146 mm HL, 600 mm TL), NMNZ P.039957 (139 mm HL, 611 mm TL) Macquarie Ridge, 51º 8' S, 161º 29' E, 853–1364 m, FV San Aotea II, Obs 1836/005, 12 Nov 2003; NMNZ P. 040586 (207 mm HL, 910 mm TL), Pacific-Antarctic Ridge, 64º 28' S, 177º 32' E, 1100–1455 m, FV Avro Chieftain, Obs 1742/ 0 97, 14 Apr 2003; NMNZ P. 041359 (152 mm HL, 665 mm TL), NMNZ P. 041360 (162 mm HL, 763 mm TL), De Gerlache Seamount, 65º 19' S, 90º 37' W, 1233–1407 m, FV Avro Chieftain, Obs 2009/084, 14 Feb 2005; NMNZ P. 041361 (162 mm HL, 696 mm TL), De Gerlache Seamount, 65º 19' S, 90º 25' W, 1055–1340 m, FV Avro Chieftain, Obs 2009/087, 15 Feb 2005; NMNZ P. 042247 (147 mm HL, 599+ mm TL), Pacific-Antarctic Ridge, 62º 22' S, 167º 6' E, 1365–1386 m, FV San Aotea II, Obs 2184/123, 15 Feb 2006; NMNZ P. 042248 2, 167– 187 mm HL, 749–835 mm TL), Pacific-Antarctic Ridge, 62º 31' S, 168º 28' E, 1180–1241 m, FV San Aotea II, Obs 2184/120, 13 Feb 2006; NMNZ P. 042573 (162 mm HL, 715 mm TL), NMNZ P. 042574 (145 mm HL, 632+ mm TL), NMNZ P. 042575 (2, 130– 153 mm HL) West of South Georgia, 53º 16' S, 41º 55' W, 1200 m, FV San Aspiring, Obs 2234/235, 28 Aug 2006; NMNZ P. 042585 (113 mm HL, 494+ mm TL), NMNZ P. 042586 (144 mm HL, 641 mm TL) South Georgia, 54º 39' S, 39º 3' W, 1260 m, FV San Aspiring, Obs 2234/123, 0 6 Jul 2006; NMNZ P. 042588 (144 mm HL, 611+ mm TL), South Georgia, 55º 10' S, 36º 22' W, 1250 m, FV San Aspiring, Obs 2234/ 128, 0 9 Jul 2006; NMNZ P. 042589 (154 mm HL, 605+ mm TL), South Georgia, 55º 12' S, 42º 15' W, 1430 m, FV San Aspiring, Obs 2234/228, 22 Aug 2006; NMNZ P. 042590 (112 mm HL, 482+ mm TL), South Georgia, 53º 13' S, 42º 21' W, 1410 m, FV San Aspiring, Obs 2234/234, 25 Aug 2006; NMNZ P.045188 (185 mm HL, 810 mm TL), Pacific-Antarctic Ridge, 62º 31' S, 168º 28' E, 1180–1241 m, FV San Aotea II, Obs 2184/120, 13 Feb 2006.

Counts and measurements ( Tables 1 –2).

Description (Figures 8–9, Tables 1 –2). Head large, length 3.6 to 4.7 into total length. Very strong scutes on head ridges, armed with strong spinules. Slightly elongated snout, length less than orbit diameter, tipped with a strong scute. Prominent strong scutes on angles of snout where nasal ridge meets suborbital ridge. Upper jaw about same length as orbit diameter, posterior end of premaxilla below or just behind mid-orbit. Chin barbel about onethird of orbit diameter.

Teeth in both jaws small, pointed. Upper jaw teeth in 4–5 rows with outer teeth not noticeably enlarged relative to those of inner rows. Lower jaw with 3–4 rows at tip, reducing to 2–3 posteriorly, outer teeth not noticeably enlarged.

Origins of pectoral and pelvic fins about on same vertical, and both slightly in advance of origin of first dorsal fin.

Body scales large, thick, adherent. Those between lateral line and first dorsal fin base with a long central row of enlarged strong spinules with 3–5 lateral ridges that lack spinules. Scales lateroventrally on body and tail with a central row of strong spinules. Dorsal head covered with heavy, spinulated, adherent scales, except for scaleless area around nostrils extending dorsally to nasal ridge and ventrally to suborbital ridge. Ventral surface of head entirely or mostly scaleless but up to 8 small patches of scales (usually less than about 10 small scales per patch) may be present at posterior end of head, beside articulation of lower jaw, beside posterior end of premaxilla, and rarely on posterior half of lower jaw.

Fresh colour of head and body dark brown. No obvious dark abdominal area in large individuals. Lining of mouth greyish-black and gill cavity blackish. Ventral surface of head dark greyish-brown. Fins greyish or blackish. Preserved specimens dark brownish.

Size. To at least 910 mm TL, and about 4.9 kg.

Distribution ( Figure 5 C). Probably widespread in temperate to Subantarctic waters of the southern hemisphere and northern Southern Ocean including the South Atlantic Ocean off the east coast of South America, South Georgia, Discovery Tablemount ( Golovan & Pakhorukov, 1983; Trunov, 1986), southwest Pacific Ocean ( Macquarie Ridge, Pacific-Antarctic Ridge), southeast Pacific Ocean off Chile (Ruiz R. & Oyarzun G., 1993), De Gerlache Seamount, at 850–2000 m. Two specimens captured on the north end of the Macquarie Ridge (NMNZ P.039949, P.039957) represent a new record of the species from the New Zealand EEZ.

Comparisons and remarks (Table 3). Macrourus caml , M. carinatus , and M. whitsoni all have a mostly scaled ventral surface of the head. M. caml , and M. whitsoni have much smaller body scales, 30–40 and 36–45 respectively in a diagonal row from anal fin origin to lateral line. M. carinatus has an outer row of enlarged teeth in the upper jaw and is generally pale to medium brown. M. berglax is known only from the northern hemisphere north of about 37° N, has pelvic fin with 8 (rarely 9) rays, large body scales with 13–17 diagonal rows from anal fin origin to lateral line, and 14–23 pyloric caeca.

Figures

FIGURE 5. Distribution maps for southern hemisphere species of Macrourus based only on specimens examined in this study. (A) M. caml sp. nov.; (B) M. carinatus; (C) M. holotrachys; (D) M. whitsoni.