Gibberichthys latifrons (Thorp, 1969)

Ho, Hsuan-Ching, Su, Yo, Leung, Nok-Sum & Lin, Tzu-Yung, 2023, New records of a rare gibberfish, Gibberichthys latifrons (Stephanoberyciformes, Gibberichthyidae), from the South China Sea, with comments on morphological characters, ZooKeys 1172, pp. 47-59 : 47

Gibberichthys latifrons (Thorp, 1969)

Figs 1 , 2 , 3

Kasidoron latifrons Thorp, 1969: 63, figs 1-4 (type locality: Western Indian Ocean off Zanzibar, Tanzania, 8°34'S, 42°37'E, from stomach content of lancetfish).

Gibberichthys latifrons (Thorp, 1969): de Sylva and Eschmeyer 1977: 228; Kotlyar 1991: 26, 1996: 259, 2002: 478; Causse 2005: 91; Okiyama et al. 2007: 45.

Material examined.

DOS 08997 (1, sex indeterminate, 49.6 mm SL), 27 Aug. 2021, coll. N.-S. Leung. DOS 09023 (1, sex indeterminate, 77.6 mm SL), 13 Oct. 2022, c. 400 m, coll. N.-S. Leung. NMMB-P37435 (1 male, 100.7 mm SL), bottom trawl, 26 Dec. 2022, coll. K.-H. Wu. NMMB-P37470 (1 female, 103.0 mm SL and 2 males, 97.2, 101.0 mm SL), bottom trawl, c. 400-500 m, 29 Jan. 2023, coll. H.-C. Ho. NMMB-P37945 (1, sex indeterminate, 82.2 mm SL), 11 Feb. 2023, coll. Y.-M Huang. All from off Dong-gang , Pingtung, southwestern Taiwan. Otoliths: CHLOL21943, taken from NMMB-P37470, 101.0 mm SL, 1.92 mm and 2.03 mm in length. CHLOL22021, taken from NMMB-P37470, 97.4 mm SL, 2.01 mm and 2.12 mm in length .

Description of Taiwanese specimens.

Tables 1 , 2 provide morphometric and meristic data.

Dorsal-fin elements 5-7 (fixed spines) + 1-2 (movable spines) + 8-9 (soft rays), all rays branched (1 specimen with first ray simple). Pectoral-fin elements 13-14 (1 with 15 in one side), upper and lowermost rays unbranched, others branched. Pelvic-fin elements I, 4-6, spine short and movable, slightly recurved, all rays branched. Anal-fin elements 2-4 (fixed spines) + 1-2 (movable spines) + 7-8 (soft rays). Principal caudal-fin rays 10 + 9, uppermost and lowermost rays unbranched; procurrent caudal-fin rays 7-8 and 6 on upper and lower lobes, respectively. Gill rakers on 1st arch 5-6 + 13-15 = 18-21; on 2nd arch 4-5 + 12-13 = 16-18; on 3rd arch 2 + 10-11 = 12-13; and on 4th arch 0 + 6-8 = 6-8. Lateral line with c. 32-36 vertical branches (some damaged); scale rows along lateral line c. 40-44 (many lost); scale rows above lateral line 5-7; scale rows below lateral line c. 18-21. No abdominal scutes. Pyloric caeca 9-13 (n = 4). Vertebrae 12-13 + 18-20 = 30-32 total (n = 7); branchiostegal rays 9; interneural 3, upper ends slightly extended upwards on dorsum forming three bumps.

Body moderately long, rather thick, depth at dorsal-fin origin 2.9-3.7 in SL. Head large, length 2.3-2.7 in SL, its height clearly less than its length, 1.3-1.5 in HL; upper profile of head convex, gently curved to dorsal-fin origin; forehead convex and broad, HF1 8.1-10.2 and HF2 4.3-4.6 in HL; eyes small, width 3.7-5.5 in HL; snout convex and short, not extending before premaxilla, length 2.5-3.2 in HL; interorbital space broad, width 2.0-2.5 in HL; postorbital length 1.9-2.1 in HL.

Mouth large, upper-jaw length 1.6-1.7 in HL; posterior end of maxilla rounded, slightly beyond vertical through posterior margin of eye; lower-jaw length slightly larger than upper-jaw length, 1.5-1.6 in HL. Upper jaw overhanging lower jaw completely. Two nostrils at same horizontal level, anterior nostril at about middle of snout; posterior nostril oval, much larger than anterior nostril, right in front of eye. Symphysis of premaxillae forming deep notch, edentate. Symphysis of dentaries with small blunt knob and edentate. Supramaxilla single, with long needle-like process extending anteriorly and long rectangular process posteriorly; covering about third of posterior portion of maxilla in width.

Spiny ridges associated with skull ridge present on head (including snout, jaws, cheek, chin, and gill cover), nape, and pectoral girdle. A small rounded fenestration on each side of supraorbital region, usually covered by skin and can only be observed when skin removed. Outer premaxillary surface completely exposed, extending almost to posterior end of maxilla and bearing villiform teeth along entire length, except for largely naked on middle areas of anterior half, followed by narrow tooth band on posterior half of the bone. Dentary completely covered by upper jaw when mouth closed; a narrow band of villiform teeth extending over about 3/4 of upper jaw. Palatine and vomer toothless.

Gill rakers rod-shaped with pointed tip, somewhat laterally compressed, covered with small teeth on inner surfaces; rakers in outer row of first arch longer than remainder, longest gill raker about equal in length to eye diameter; no raker on inner surface of first arch; gill rakers in outer row of second arch slightly shorter than those in outer row of first arch; gill rakers in outer row of third arch shorter than those in two anterior arches; low knobs present in inner rows of second and third arches; single row of short, somewhat knob-like rakers on fourth arch. Tooth patch present on fifth ceratobranchial. Long, oval tooth patch on third epibranchial arch. Large, triangular villiform tooth patch on second pharyngeal arch and small irregularly triangular tooth patch on third pharyngeal arch. Gill filaments on first arch short, about half length of longest opposite rakers.

Body covered with cycloid scales, all embedded under thin skin. Head entirely naked. Lateral-line scales not distinct from neighboring scales.

Dorsal fin low, with long base, length of dorsal-fin base 3.2-3.7 in SL. Pectoral fin short, its length 2.3-2.5 in HL, tip slightly pointed, reaching to or slightly beyond vertical through anal-fin origin. Pelvic fin short, its length 3.5-4.1 in HL, tip reaching anal-fin origin. Anal fin moderately small, its base length 1.7-2.0 in HL. Caudal fin moderately large, forked, its length 2.2-2.7 in HL.

Lateral line single, originating behind posttemporal bone; its anterior portion slightly curving down, running along dorsal profile on about upper fifth of body, with nearly straight posterior portion ending at caudal-fin base. Clear but weak lateral-line canal along surface of body, with about 32-36 pairs of pale upper and lower vertical extensions, each bearing about 3 papillae (partly damaged by trawl operation in examined specimens).

Anus situated anteriorly, between middle of pelvic fins, clearly anterior to anal-fin origin. Light organ absent. Caudal peduncle long, rather thick, its length 1.4-1.7 in HL, height 3.3-6.1 in HL.

Otolith morphology.

Sagittal otoliths were taken from NMMB-P37470, 101.0 mm SL (right: 1.92 mm in length x 2.17 mm in width, left: 2.03 x 2.20) and 97.2 mm SL (right: 2.01 x 2.26, left: 2.12 x 2.28) (Fig. 3 ). Otolith tall, somewhat bilobed, ventral lobe more developed than dorsal lobe, its width 1.9-2.2% SL, length/depth ratio 0.88-0.93. Dorsal margin highly convex, smooth with 3 or 4 indistinct lobes; ventral margin curved with slight wave; posterior margin entire, slightly convex with a shallow excisura caudalis, pseudo-excisura and pseudo-rostrum poorly developed; distal surface slightly convex, rather smooth; proximal surface slightly concave; sulcus groove deep and wide, with a large ostium opening dorso-anteriorly; ostial colliculum oval, surrounded by broad crista superior and crista inferior; no cauda or caudal colliculum; rostrum broadly rounded; antirostrum rounded, poorly developed; a shallow notch on excisura; dorsal depression deep and broad; ventral depression absent.

Coloration.

When fresh, body dark brown to black mixed with deep red color. Mouth cavity and gill chamber orange-red. When preserved, body uniformly black with pale mouth cavity and gill chamber. Stomach and pyloric caeca white, intestine orange-red on anterior half, paler on posterior half. Peritoneal membranes light orange-red on pale gray background. Mouth cavity and gill chamber orange-red on bluish gray background.

Maturity.

The largest specimen (103.0 mm SL) is a mature female with two large ovaries containing many large, loose eggs (c. 0.6-0.7 mm). Three other specimens (97.2, 101.0 and 100.7 mm SL) are mature males with well-developed testis.

Distribution.

Originally described from the western Indian Ocean ( Thorp 1969) and recorded from scattered localities, including Japan, Vietnam, Ceram Sea, Halmahera Sea, New Guinea Sea, off Molucca, Marquesas, Samoa Islands, Comoro Islands, Madagascar, Saya de Malha Bank, and the East Indian Ridge; bathymetric range 320-1700 m ( Kotlyar 2002; Causse 2005; Okiyama et al. 2007). Our specimens were collected from depths about 400-500 m by bottom trawl.

Figures

Figure 1. Gibberichthys latifrons (Throp, 1969), fresh condition. A-C NMMB-P 37470: female, 103.0 mm SL (A), male, 101.0 mm SL (B), male, 97.2 mm SL (C) D NMMB-P 37435: male, 100.7 mm SL E DOS 08997: 49.6 mm SL.

Figure 2. Preserved specimens of Gibberichthys latifrons (Throp, 1969). A-E same specimens as in Fig. 1.

Figure 3. Otoliths of Gibberichthys latifrons (Throp, 1969). A, B CHLOL 21943, from NMMB-P 37470, 101.0 mm SL C, D CHLOL 22021, from NMMB-P 37470, 97.2 mm SL. A, C left otolith B, D right otolith. 1 inner surface, 2 outer surface. Scale bar: 1 mm.