Hoplostethus grandperrini, Roberts & Gomon, 2012

Roberts, Clive D. & Gomon, Martin F., 2012, A review of giant roughies of the genus Hoplostethus (Beryciformes, Trachichthyidae), with descriptions of two new Australasian species., Memoirs of Museum Victoria 69, pp. 341-354 : 351-353

Hoplostethus grandperrini sp. nov.

Grandperrin’s giant sawbelly

Figures 2 , 5 & 6 ; Tables 1 & 2

Hoplostethus cf. g igas: Grandperrin & Lehodey, 1992: 7, 26 and 35, listed, seamount “B”, Norfolk Ridge, New Caledonia.

Holotype. NMNZP.027462 (455) New Caledonia, Norfolk Ridge , Seamount “B”, 24°55.15'S, 168°20.95'E, 600–675 m, BERYX 2 , stn 3, N.O. Alis, chalut à poissons (= fish bottom trawl), 24 October 1991, R. Grandperrin and C. Roberts. (Lodged in NMNZ collection at the request of MNHN).

Paratype. MNHN 2012–0269 (131) New Caledonia, SE slope of Grande Terre , 22°13.00' S, 167°14.00' E, 500–510 m, MUSORSTOM 4, stn 238, N.O. Vauban, chalut à perche (= beam trawl), 2 October 1985 .

Diagnosis. Pectoral–fin rays 17 or 18; total gill rakers on outer side of first arch 19 or 20; abdominal scutes 13 or 14, scutes rectangular and rugose in large individuals; predorsal scales, 21–24; isthmus lacking scales; body scales adherent; lateral line scales with strong medial ridge and spine posteriorly and with numerous fine rather long spines in small individuals, scales rugose, lacking a posterior spine in large adults; scales on predorsal midline forming very low ridge in small individuals, no ridge apparent in very large individuals; body ovoid and deep, depth 1.8–1.9 in SL; dorsal profile of head gently curved; dorsal– and anal–fin spines of moderate thickness; pectoral fin of moderate length, reaching base of second anal–fin spine in small individuals, to tenth or eleventh abdominal scute in largest; adults orange–red; buccal cavity mostly white, black only on roof of mouth posteriorly, opercular recess black anteriorly, much paler near periphery. Reaches 455 mm SL.

Description. (See Table 1 for frequencies of values for selected meristic characters.) Dorsal–fin rays VI, 13; anal–fin rays III, 9; caudal–fin rays 6 + 2 + 9 + 8 + 2 + 6; pectoral–fin rays 17 (18 in 1 of 4); pelvic–fin rays I, 6; gill rakers 6 + 1 + 13 (6 + 1 + 12); lateral–line scales 28 + 1; transverse scales 12/1/26 (11/1/35); predorsal scales 21 (24); scutes 14 (13; Table 2); vertebrae 11 + 15; pseudobranch 15 (only holotype examined); branchiostegal rays 8.

(See Table 1 for comparative ranges of selected morphometric characters.) Body ovoid and deep, depth 1.8–1.9 in SL. Head large, its height equal to or slightly greater than its length, 99.1–103% HL; upper profile in front of dorsal fin gently curved to upper jaw; anterodorsal profile moderately separated from upper orbital rim; space between eyes wide, interorbital width 31.1–34.0% HL; eye of moderate size, orbital diameter 23.2– 29.18% HL; crests of head bones strong, fine spinules on apices at skin surface; depressions between crests moderately deep, hidden by thick skin in adults; infraorbital bones becoming progressively broader with growth; nostrils immediately preceding orbits, posterior nostril two to four times area of anterior nostril; mouth reaching just beyond vertical through hind margin of eye; large, fine denticulate teeth covering oral margins and exposed lateral surfaces of premaxilla and dentary, palatine with narrow band of similar teeth, vomer apparently lacking teeth (with three small teeth in 131 mm paratype); tip of dentary with ossified knob at symphysis. Preopercular spine short and rounded (slender and pointed, reaching to pelvic-fin base in small individual). Humeral spines short and rounded (short and pointed in smallest individual). Longest gill raker about 2/3 eye diameter; gill filaments at angle of first gill arch very short, about 1/10 eye diameter and just less than 1/2 length of longest filaments of pseudobranch.

Body covered with adherent scales, those above lateral line, posteriorly and low on side densely covered by rather long fine spines, scales above and covered laterally by pectoral fin, cycloid (cycloid scales distributed more ventrally in smaller individual); head naked except for patch of scales on cheek posterior to rear tip of maxilla in about three or four vertical rows, posteriormost row with 13 or 14 scales; isthmus scaleless; lateral–line scales rugose, without a strong spine (smaller individual having each lateral–line scale with slender ridge and small pointed spine posteriorly, peripheral row of spinules noticeably longer than others); low serrated abdominal keel formed from slightly rugose, enlarged scales (scutes) with pointed apices (smaller individual with smooth scutes more typical of other species), scales on midline preceding scutes somewhat enlarged but not counted as scutes above; scales on dorsal midline in front of dorsal fin not forming low ridge (smaller specimen with posterior scales slightly raised medially), their spinules not enlarged. First dorsal–fin spine short, second and third spines progressively longer, last three increasing in length only slightly; spines of moderate thickness, those posteriorly progressively thicker with distinct lengthwise striations; first soft ray longer than last spine, subsequent rays progressively decreasing in length, outer margin of soft dorsal fin slightly curved. First anal–fin spine short, second short or of intermediate length, and third long; spines of similar robustness to those in dorsal fin. Caudal fin distinctly forked, lobes broad and rounded. Pectoral fin of moderate length reaching tenth or eleventh abdominal scute (reaching base of second anal–fin spine in smaller individual). Pelvic fin reaching to middle scutes (to eighth scute in smaller individual).

A large species, largest specimen examined 455 mm SL.

Colour in life. Head orange–red; body orange–tan dorsally, extending ventrally to pelvic–fin base anteriorly and to anal–fin base posteriorly; opercle black suffused with red; dark areas of buccal and branchial cavities black, pale areas stark white; fins orange to orange–tan, without darker margins (fig. 6).

Pigmentation in alcohol. Freshly preserved individuals grey–tan; opercle dark; buccal chamber pale, roof dark posteriorly; fins pale, outer edge of membranes between dorsal–fin spines dusky. Etymology. The specific name grandperrini recognises Dr René Grandperrin, retired chief scientist of ORSTOM Nouméa, ardent fish researcher and leader of deepwater fish explorations off New Caledonia (Chef de Mission of research cruises BERYX 2 and HALIPRO2),in recognition of his strong support for collaborative fieldwork between French and New Zealand scientists.

Distribution. Known only from the types collected at Seamount “B” in the northern portion of the Norfolk Ridge, south of New Caledonia and on the south-eastern slope of New Caledonia’s Grande Terre (fig. 2), from depths of 500– 675 m.

Comments. The great similarity of many Hoplostethus species to one another has led to confusion about the identity of this species with two other apparently undescribed species living on seamounts in waters off southern New Caledonia. At least one of the latter reaches a considerable size, the largest known specimen measuring 355 mm SL, and has a distribution that includes Australian territorial waters. The three are consistently separable by a combination of characters, including numbers of pectoral– fin rays and abdominal scutes, and the pigmentation of the buccal cavity. The identities of the other two species will be the subject of a forthcoming publication by Gomon and Roberts (ms).

With regard to the three New Caledonian species we recognise, G. grandperrini has 17 or 18 pectoral–fin rays (versus 16 or 17, rarely 15 or 18, and 15, rarely 16 in the other two), 13 or 14 abdominal scutes (versus 10–15 and 11–13 scutes) and has a buccal cavity that is mostly pale, any black pigmentation confined to the rear of the mouth in the vicinity of the throat (versus buccal cavity entirely black behind the oral valves, including the underside of the tongue and top of the lower jaw, and buccal cavity black with vomer, underside of the tongue and the top of the lower jaw white). These same character combinations, plus high count of predorsal scales (21–24 versus 9–15, 16–22), separate H. grandperrini from the other two giant species treated above. Based on the limited series of types, H. grandperrini also appears to have a greater body depth, postorbital length, interorbital width, and pelvic fin to anal fin distance (fig. 5).

Of the remaining nominal species referred to the subgenus H. ( Hoplostethus ) apparently only two regularly have 17 or 18 pectoral–fin rays, H. druzhinini Kotlyar, 1986 in the Arabian Sea and H. vniro in the southeastern Atlantic. Both of these species differ from H. grandperrini in having on average more numerous gill rakers, 21–25, versus 19 or 20. In addition, H. duzhinini has only 8–12 abdominal scutes (versus 13–14) and a mostly black buccal cavity (versus mostly pale).

Figures

Figure 2. Collection localities for specimens examined of Hoplostethus gigas (squares), H. melanopeza sp. nov. (circles) and H. grandperrini sp. nov. (diamonds). Red symbols indicate holotypes or lectotype.

Figure 5. Selected proportional measurements relative to standard length for Hoplostethus gigas, H. melanopeza sp. nov. and H. grandperrini sp. nov.

Figure 6. Hoplostethus grandperrini sp. nov., NMNZ P.027462, 455 mm SL, holotype. A, fresh, photo by C. Roberts. B, preserved, photo by C. Struthers.