Hoplostethus grandperrini Roberts & Gomon, 2012

Su, Yo, Lin, Hsiu-Chin & Ho, Hsuan-Ching, 2023, New records of two roughy fish species of Hoplostethus and a confirmed record of H. crassispinus Kotlyar, 1980 (Trachichthyiformes, Trachichthyidae) from Taiwan, ZooKeys 1149, pp. 85-101 : 85

Hoplostethus grandperrini Roberts & Gomon, 2012

Figs 1 , 2 , 3A

Hoplostethus grandperrini Roberts & Gomon, 2012: 351 (type locality: New Caledonia, Norfolk Ridge, 24°55'8.99"S, 168°20'56.99"E, depth 600-675 m).

Hoplostethus cf. gigas - Grandperrin and Lehodey 1992: 7, 26, 35.

Material examined.

NMMB-P 36039, 395 mm SL, off the coast of Shan-hai fishing port, Pingtung, southwestern Taiwan (ca 21°59'08.75"N, 120°42'42.03"E), 19 April 2014, hook and line, purchased by C.-W. Chang .

Description of NMMB-P36039.

Meristic and morphometric values are provided in Tables 1 , 2 .

Dorsal-fin rays VI, 13; pectoral-fin rays 17/17; pelvic-fin rays I, 6/I, 6; anal-fin rays III, 9; principal caudal-fin rays 10+9=19, uppermost and lowermost rays unbranched; procurrent caudal-fin rays 7 dorsally and 7 ventrally; gill rakers on outer surface of first-gill arch 6+1+13=20; lateral-line scales 28; scale rows between dorsal-fin origin and lateral line 13, scale rows between anal-fin origin and lateral line 23; predorsal scales 24; abdominal scutes 17; vertebrae 11+16=27; pyloric caeca 44; pseudobranchial filaments 30; branchiostegal rays 8; supraneural and pterygiophore insertion formula: 0/0/2+1/1/1/1 (spinous dorsal fin only).

Body oblong, distinctly longer than deep, depth at dorsal-fin origin 2.0 in SL. Head large, its length 2.7 in SL, its height subequal to its length, 1.0 in HL; upper profile in front of dorsal fin slightly curved to back of head, with somewhat concave forehead, and abrupt downturn above maxilla; forehead broad, HF1 11.9 and HF2 5.6 in HL; eyes of moderate size, 3.7 in HL; snout length 4.6 in HL; space between eyes convex and broad, interorbital width 2.8 in HL; crests on head bones well developed and covered with rather long spinules.

Mouth large, posterior end of maxilla extending beyond vertical through posterior margin of eye. Nostrils right before anterior margin of eye, on horizontal about through center of eye; posterior nostril distinctly larger than anterior nostril; eyes rather ventrally placed, upper margin of eye on horizontal through lateral-line origin.

Most of lateral and medial surfaces of premaxilla and dentary covered with villiform teeth, those on medial surface rather conical; no teeth at symphyseal notch of premaxilla and knob at symphysis of dentaries. Narrow band of villiform teeth on palatine; vomer toothless. Gill rakers on first and second arch rod-shaped, laterally compressed, with small conical teeth on tips and inner surfaces; those in outer row of first arch longest; those on inner row of first arch and both inner and outer rows of second and third arches short; small tooth patches, forming bumps on midline of outer three arches; large tooth patches present on fourth ceratobranchial arch. Large, oval patch of villiform teeth on fifth ceratobranchial. Large, slightly oval tooth patch on second pharyngobranchial. Large teardrop-like tooth patch on third pharyngeal arch.

Preopercular spine short, its tip not reaching pelvic-fin base. Longest gill raker 0.7 in eye diameter; gill filaments at angle of first gill arch very short, ca 4.3 in eye diameter, and ca 1.8 in length of longest pseudobranchial filaments.

Body scales firmly attached, cycloid scales present on pectoral-fin region, elsewhere covered with ctenoid scales armored with rather long spinules (Fig. 2A ); isthmus and gular region naked; lateral-line scales enlarged, ca 2-3 times size of body scales; center of each lateral-line scale without distinct spine; enlarged scales (scutes) covering abdomen region, their bases covered with body scales, all scutes with single tip; predorsal scales not enlarged and not forming distinct ridge (Fig. 2B ).

Dorsal-fin spines progressively longer posteriorly, greatest increase in length from first to fourth spine; first ray unbranched, others branched; outer margin of dorsal-fin rays nearly straight. Pectoral fin truncated, slightly rounded; short, not reaching vertical through anal-fin origin. Pelvic fin short, reaching 11th abdominal scute. Pyloric caeca pale, unbranched.

Coloration.

Fresh coloration unknown, presumably a reddish body color as shown by Roberts and Gomon (2012: fig. 6). Preserved specimen uniformly pale, slightly yellowish (Fig. 1 ), membranes on head region lighter than body color. Anal- and caudal-fin rays with black pigmentation near base (Fig. 2C ). Oral cavity, including underside of tongue white, with very scarce black pigmentation (Fig. 3A ). Inner side of opercle black. Peritoneum and stomach black.

Distribution.

Previously, only type series collected between 600 and 675 m deep off the coast of New Caledonia were known. Our specimen represents the second record and a range extension to the Northern Hemisphere, suggesting a wide distribution in the western Pacific Ocean.

Remarks.

The present specimen was identified as H. grandperrini by having a pale oral cavity, a short pectoral fin with its tip not reaching a vertical through the anal-fin origin, predorsal scales not enlarged and forming a distinct ridge, head bones covered with long spinules, ctenoid scales on body with rather long spinules, and a larger size, exceeding 300 mm SL ( Roberts and Gomon 2012).

Hoplostethus grandperrini can be distinguished from other species of Hoplostethus co-occurring in Taiwan by having the following characters: a pale oral cavity, including the underside of the tongue (vs uniformly black oral cavity in both H. japonicus and H. roseus ), a short pectoral fin with its tip not reaching a vertical through the anal-fin origin (vs a long pectoral fin exceeding beyond a vertical through the anal-fin origin in H. japonicus and H. sp.; sensu Su et al. 2022).

In comparison to the data provided by Roberts and Gomon (2012), our specimen has a higher number of abdominal scutes (17, vs 13-14) and pseudobranchial filaments (30, vs 15), a slightly lower number of lateral-line scales (28, vs 29) and fewer scale rows below the lateral line (23, vs 26-35), and some slightly different morphometric characters (e.g., smaller head length, prepectoral length, and prepelvic length; Tables 1 , 2 ). These values are rather distinct, and additional research may reveal whether the Taiwanese population represents a different species. It is also notable that the forehead length (HF2) of our species is 6.7%, distinctly different from 41.0-44.2% SL provided by Roberts and Gomon (2012). Based on our previous data (e.g., 3.7-7.9% SL in specimens examined by Su et al. 2022), it is likely that they were referring to "head height" rather than "forehead height".

Figures

Figure 1. Hoplostethus grandperrini Roberts & Gomon, 2012. NMMB-P 36039, 395 mm SL, Pingtung, Taiwan.

Figure 2. Hoplostethus grandperrini, NMMB-P 36039, 395 mm SL A scales on the dorsal side of the body featuring long spinules B predorsal scales C caudal-fin pigmentation. Figs not to scale.

Figure 3. Coloration of oral cavities of Hoplostethus species A H. grandperrini, NMMB-P 36039, 395 mm SL, preserved B H. robustispinus, FRIP 01364, 241 mm SL, preserved.