Gnathophis asanoi Karmovskaya, 2004

Ho, Hsuan-Ching, Smith, David G. & Huang, Jian-Fu, 2018, Notes on two rare conger eel species (Anguilliformes: Congridae) found in Taiwanese waters, Zootaxa 4454 (1), pp. 233-237 : 235-237

Gnathophis asanoi Karmovskaya, 2004

Figs. 2A–C

Gnathophis asanoi Karmovskaya, 2004 :S18, fig. 10 (type locality: Philippines, Sibuyan Sea, 280‒440 m). Ho et al., 2015:147.

Specimen examined. NMMB-P 25987, 291 mm TL, 13 Oct. 2017, coll. H.-C. Ho; USNM 401080, 343 mm TL, 25 May 2010, coll. H.-C. Ho & Y. Yamanoue; both from Dong-gang, southern Taiwan, South China Sea, bottom trawl.

Description of Taiwanese specimens. Head length 14.4‒15.3% TL; preanal length 35.1‒37.9; predorsal length 16.8‒17.3; trunk length 20.2‒22.6; tail length 61.8‒64.9; depth at head ~4.2; depth at anus 3.4‒4.8; width at anus ~2.7. Snout length 31.3‒33.5% HL; eye diameter 14.7‒20.6% HL; interorbital width ~11.2; rictus 35.4‒41.1; gill opening width 10.5‒11.8; interbranchial width 19.6‒20.2; pectoral-fin length 23.9‒24.2.

Body moderately elongate, cylindrical in cross section anteriorly, becoming more compressed posteriorly; tip of tail moderately attenuate; anus slightly behind anterior third of total length. Dorsal-fin origin slightly ahead tip of appressed pectoral fin, continuous around tip of tail with caudal and anal fins. Anal fin begins immediately behind anus. Pectoral-fin well developed, pointed distally with narrow base. Gill opening relatively small, smaller than eye diameter, its upper end nearly opposite middle of pectoral-fin base; interbranchial broader than gill opening and eye.

Head moderately large reflected by the less slender body, deepest at about gill opening; snout long and pointed, its length 1.6‒2.1 times eye diameter, projecting well beyond lower jaw; lower jaw clearly shorter than snout; fleshy part of snout projecting anteriorly beyond anterior end of intermaxillary tooth patch; rictus below anterior half of eye. Anterior nostril tubular, near tip of snout, directed ventrolaterally. Posterior nostril elliptical, with a slightly raised rim, in front of eye at mid-eye level. Upper lip with a shallow, free, upturned flange, beginning at second infraorbital pore and ending below middle of eye. Lower lip with a well-developed downturned flange. Tongue free, long, and narrow.

Lateral-line complete, first pore on each side slightly enlarged, the canal extended to caudal-fin base; 6 before pectoral-fin base, 10 before dorsal-fin origin, 33‒36 pores before anal-fin origin; and ca. 127 total pores (based on NMMB-P 25987); no elevated pores above pectoral fin.

Head pores small ( Fig. 2B ); supraorbital canal with 5 pores, the first (ethmoidal pore) and second on ventral side of tip of snout, just ahead the lip. Infraorbital canal with 7 pores, first 4 along the upper lip and the fifth behind the rictus; 2 pores behind eye. No pore on frontal. Preopercular canal with 2 pores; mandibular pores 7, 6 along lower jaw and the last well behind rictus. Supratemporal commissure with 3 pores, the middle one tiny. Predorsal vertebrae 10; preanal vertebrae 34‒36; precaudal vertebrae ~42; total vertebrae 137‒141.

Teeth small, conical to blunt ( Fig. 2C ). Intermaxillary in about four transverse rows, connected to maxillary and vomerine teeth. Maxillary and mandibular teeth in bands, wider anteriorly, roughly in 4‒5 rows, narrower posteriorly. Vomerine teeth blunt, forming a long patch, in about 4 transverse rows.

Coloration. When fresh, body light grayish with dorsum darkly brown and abdomen silvery white; posterior fifth of body gradually darker; vertical fins whitish, forming white margin on posterior fifth of the fish. Preserved specimen paler.

Remarks. The vertebral formula and most proportions fit the original description. However, a number of differences are present in Taiwanese specimens. The 343 mm specimen has slightly larger values of preanal length (37.9 vs. 34.3‒35.7% TL in type series) and trunk (22.6 vs. 19.7‒19.9% TL), smaller eye (14.7 vs. 15.7‒17.8% HL) and 137 total vertebrae (vs. 139‒140). The 291 mm specimen has a larger eye (20.6 vs. 15.7‒17.8% HL). Both Taiwanese specimens have smaller gill openings (10.5‒11.8 vs. 14.3‒14.7% HL) and shorter pectoral fin (23.9‒24.2 vs. 28.6‒29.4% HL). There are only 9 POM pores in 291 mm specimen. We are not able to judge these differences, as not many specimens are available at present. More specimens are needed to address the variation of the present species.

Four species of Gnathophis Kaup, 1859 are currently known from the northwestern Pacific: G. heterognathus ( Bleeker, 1858) , G. ginanago ( Asano, 1958) , G. xenica ( Matsubara & Ochiai, 1951) , and G. asanoi . Of these, G. heterognathus has the widest distribution, from Japan to the Philippines ( Karmovskaya, 2004). Gnathophis ginanago and G. xenica have been recorded only from Japan, and G. asanoi is now known from the Philippines and Taiwan. Gnathophis heterognathus is distinguished from the others by the presence of elevated lateral-line pores (i.e., opening from the top of the canal rather than the bottom) over the pectoral fin; in the others, the pores open from the bottom of the canal. The remaining species are distinguished by their vertebral counts: 126‒134 in G. ginanago , 137‒141 in G. asanoi , and 151‒157 in G. xenica .

Our specimens represent the only known specimens other than the type series and extend the known range of the species northward to southern Taiwan.

Figures

FIGURE 2. Gnathophis asanoi Karmovskaya, 2004, NMMB-P25987, 291 mm TL. A. lateral view. B. head pore, by Y.-C. Tu. C. tooth pattern, upper jaw (left) and lower jaw (right).