Neenchelys daedalus McCosker, 1982

Ho, Hsuan-Ching, Hibino, Yusuke & Huang, Jian-Fu, 2018, Note on rare snake eels (Anguilliformes: Ophichthidae) and additional data on three Neenchelys recently described from Taiwan, Zootaxa 4454 (1), pp. 200-214 : 207-209

Neenchelys daedalus McCosker, 1982

Figure 4 ; Table 2

Neenchelys daedalus McCosker, 1982:63 , figs. 4–5 (type locality: Astrolabe Bay, south of Madang, Papua New Guinea, 5°24’S, 14°52.5’E). Hibino et al., 2012:345 (in part). Ho et al., 2013:7. Tashiro et al., 2015:5. Ho & Loh 2015:54. Hibino et al., 2015:57 (in Key).

Material examined. NMMB-P 26828 , 306 mm TL, off Dong-gang fishing port, Pingtung, southwest Taiwan,

South China Sea, 6 Feb. 2017, coll. J.-F. Huang. NMMB-P 27328, 392 mm TL, off Dong-gang fishing port, Pingtung, southwest Taiwan, South China Sea, 13 Oct. 2017, coll. H.-C. Ho.

Diagnosis. A species of Neenchelys with the following combination of characters: body elongate and relatively compressed, its depth 46¯54 times in TL; origin of dorsal fin at about midtrunk, 1.0¯1.2 times HL behind gill opening; predorsal length 6.5¯ 6.9 in TL; head 13¯ 15 in TL, trunk 4.8¯ 5.3 in TL; tail 1.3¯ 1.8 in TL; pectoral fin elongate, nearly as long as upper jaw; an enlarged blunt flap on posterior-dorsal margin of anterior nostril. Total vertebrae 225̄238, MVF 31-58-233. Mandibular pores 5̄6. Body coloration in isopropyl alcohol uniformly tan, except belly which is dark brown to black; fins colorless except darker posterior end. ( McCosker, 1982; present study)

Description of Taiwanese specimens. The following data are given for 306 mm specimen parenthetically followed by those of the 392 mm specimen.

Body very elongate, body depth at anus 50 (54) times in TL; somewhat cylindrical with tail gradually compressed posteriorly; depth of body relatively uniform, tapering gradually to tail tip; depth of head subequal to that of body. Tail slender, anus at anterior 1/4 of total length. Dorsal and anal fins low and fleshy, continuous with a small but distinct rayed caudal fin; origin of dorsal fin slightly before mid-point of trunk. Pectoral fin relatively well developed, broad at base and pointed posteriorly.

Head profile terete, relatively small, it length 14.8 (15.1) times in TL; scattered small papillae on surfaces of anterior portions of snout, lips and lower jaw; snout acute anteriorly, tip of snout projecting well beyond lower jaw, its length 5.6 (6.3) times in HL; dorsal surface of snout broad and tumid, housing an extensive nasal organ on either side. Anterior nostril tubular with an enlarged blunt flap on posterior-dorsal margin, the opening directed anteroventrally. Posterior nostril in front of lower margin of eye, opening directed ventrally, appearing in lateral aspect as a diagonal slit, the posterior end of which is highest. Behind and below nostril and parallel to it is a groove that is longer than nasal slit.

Lower jaw included, its tip reaching a line between anterior margins of anterior nostrils. Angle of gape about one eye diameter behind a vertical through posterior margin of pigmented eyeball. Tongue not free, well attached to mouth floor. Gill opening a narrow vertical slit, situated at anteroventral corner of pectoral fin base.

Head pores small ( Fig. 4C , in part). Supraorbital pores 5 (5), first pore at ventral side of tip of snout, last pore at anterior-dorsal corner of eye; infraorbital pores 6 (6), 2 pores between anterior and posterior nostrils, 2 beneath and 2 behind eye. Mandibular pores 6 (6); preopercular pores 2 (2); supratemporal pores 3 (3; if 2 side pores counted as first pore of lateral line); 1 (0) frontal pore; no adnasal pore.

Teeth slender, pointed, tips directed posteriorly ( Fig. 4D ). Intermaxillary teeth 2 (2), well separated from that of vomer; vomerine teeth uniserial, terminating posteriorly at about level of posterior margin of eye; maxillary uniserial, originating between second and third vomerine tooth, with 9̄10 (10̄11) teeth, terminating posteriorly at gape; dentary with 16 (25¯29) uniserial teeth, its end terminating at opposite maxillary tooth row.

Lateral line incomplete, pores small and inconspicuous, the canal extending to about one HL before the tail tip. Cephalic lateral- line pores 13̄14 (14), predorsal pores 34̄35 (33), preanal pores 60̄61 (61), and total pores ca. 190 (ca. 200).

Predorsal vertebrae 32 (31), preanal vertebrae 57 (59), and total vertebrae 233 (238).

Coloration. When fresh uniformly brownish gray with posterior end of dorsal and anal fin margins edged black; in preservative gray to light brown, with posterior end of dorsal and anal fins edged black.

Remarks. The species was originally described based on 2 specimens collected from Papua New Guinea. Although there is one additional record from Japan, it was proved to be a misidentification ( Ho et al., 2013, 2015). Thus our specimens represent the third specimens of this species and also the first record of northwestern Pacific Ocean.

Table 2 shows the morphometric and meristic data of two Taiwanese specimens compared to these of two types. The morphometric proportions are mostly overlapped, except for these mentioned below. In Taiwanese specimens, the eye diameter is slightly larger (6.8% vs. 5.1̄5.6% HL), the interorbital width is clearly broader (10.7̄12.6% vs. 8.4̄8.7% HL), the rictus is slightly longer (26.9̄30.0% vs. 24.3̄26.4% HL), and the body is slightly deeper and wider. The numbers of head and lateral-line pores are quite consistent, except for 6 mandibular pores in a Taiwanese specimen, whereas the types have only 5. It is notable that the types have a single frontal pore, whereas one of our specimens has one and the rest have none. YH examined the CAS paratype and found its eye diameter 7.2% HL and rictus 31.3% HL. Moreover, the CAS paratype has small papillae on its snout, lips and anterior portion of its lower jaw, similar to that of N. similis , but quite scattered in arrangement.

Our specimen has the vertebrae formula 32-57-233 (31-59-238) which is close to that of the type series.

The arrangement and number of teeth is nearly identical to that of the paratype ( Ho et al. 2013: figs. 3C, D), except there are only two intermaxillary teeth. Both of our specimens have 6 pores on each side of the mandible, instead of 5 in the type series. These two differences may be attributable to individual variation.

It is also notable that the holotype (342 mm TL) and paratype (272 mm TL) of N. daedalus are females with mature or near-mature gonads (holotype has eggs approximately 1 mm in diameter), whereas N. similis matures at more than 600 mm TL. This may indicate that N. daedalus is a smaller species.

Figures

FIGURE 4. Neeenchelys daedalus McCosker, 1982. A, B. NMMB-P26828, 306 mm TL, lateral view. C, D. NMMB-P27328, 392 mm TL. C. anterior portion of head, arrow indicates frontal pore. D. upper jaw teeth.