Neenchelys andamanensis, Hibino, Yusuke, Satapoomin, Ukkrit & Kimura, Seishi, 2015

Hibino, Yusuke, Satapoomin, Ukkrit & Kimura, Seishi, 2015, A new species of Neenchelys (Anguilliformes: Ophichthidae: Myrophinae) from the eastern Indian Ocean, Zootaxa 4060 (1) : -

Neenchelys andamanensis sp. nov.

New English name: Andaman Worm Eel Figs. 1 , 2 , 3

Holotype. PMBC 25065, 336 mm TL, sex unknown, 7°21'N, 97°26'E, off Phuket, Andaman Sea, eastern Indian Ocean, 520–531 m depth, 27 January 1999, collected by S. Bussarawit and C. Aungtonya.

Diagnosis. A species of Neenchelys with the following combination of characters: head 7.4% TL; tail 60% TL; body depth at gill opening 1.4% TL; origin of dorsal fin anterior to mid-trunk, horizontal distance from the origin to a vertical through mid-anus 65% of trunk length; interorbital width 4.5% HL; pectoral fin minute, 2.4% HL; predorsal vertebrae 36, preanal 77, and total 221.

Description. Counts: 36 predorsal, 77 preanal, and total vertebrae 221. Proportional measurements as % TL: head length 7.4; trunk length 33; preanal length 40; tail length 60; predorsal length 19; body depth at gill opening 1.4; body depth at mid anus 1.2; body width at gill opening 0.6; body width at mid anus 1.0. Proportional measurements as % of trunk length: horizontal distance from origin of dorsal fin to a vertical through mid-anus 65. Proportional measurements as % of head length: head depth 25; head width 14; eye diameter 5.3; interorbital width 4.5; snout length 14; upper-jaw length 33; mouth gape 25; gill-opening length 1.8; pectoral-fin length 2.4.

Body elongate, extremely slender, trunk subcylindrical but gradually compressed posteriorly, strongly compressed at tip of tail ( Fig. 1 ); head small; tail long, preanal length clearly shorter than tail. Snout long, deep and horizontally wide, tip of snout relatively acute, its length about 2.6 times eye diameter; small papillae distributed on tips of snout and lower jaw ( Fig. 2 a); mouth inferior, distance from tip of snout to tip of lower jaw slightly shorter than eye diameter; no prominent groove on ventral side of snout; anterior nostril tubular, short, its length half of eye diameter, with elongate flap on posterior margin of rim ( Fig. 3 ); posterior nostril as elongate slit, entirely open posteriorly, located above upper lip on anteroventral side of eye; eye small, covered by a transparent skin, located at midpoint of upper jaw; mouth large, rictus of mouth much behind a vertical through posterior margin of eye; a weak ridge on upper and lower lips; all teeth conical, pointed, and slightly recurved posteriorly; jaws and vomerine teeth uniserial ( Fig. 2 b, c); intermaxillary teeth arranged in a trapezoid; interorbital region slightly convex, without a median groove; gill opening constricted, one-third of eye diameter, located ventrolaterally, just anterior to base of pectoral fin; arrangement of cephalic sensory pores as follows ( Fig. 2 a): one + four supraorbital, four + two infraorbital, six + two preoperculomandibular, and two supratemporal; lateralline almost completed, posteriorly reaching to 1/2 head length before caudal-fin base; pores small but conspicuous, 11 anterior to pectoral-fin insertion, 36 anterior to dorsal-fin origin, 78 anterior to anus, and total 187. Dorsal and anal fins somewhat low, both fins confluent with caudal fin; origin of dorsal fin located anterior to mid-trunk; tip of caudal fin rounded, extremely short; pectoral fins minute, inconspicuous, their length shorter than eye diameter and their base less than half of gill opening.

Color of fixed and preserved in 10 % formalin. Head and body uniformly brown ( Fig. 1 ), with scattered dark spots mainly distributed along dorsal midline, lateral line, and anal-fin base; sensory pores on head relatively pale. Dorsal and anal fins pale brown, but darker posteriorly (posteriormost tail region about 1/3 head length); caudal fin dark brown and pectoral fin pale brown.

Distribution. Known from only type locality, off Phuket, southeastern Andaman Sea, eastern Indian Ocean. Etymology. The scientific name is derived from the type locality, Andaman Sea.

Figures

FIGURE 1. Holotype of Neenchelys andamanensis sp. nov., PMBC 25065, 336 mm TL, Andaman Sea. A position of anus, D origin of dorsal fin.

FIGURE 2. Lateral view of head (a), dentition of upper jaw and palatal area (b), and lower jaw (c) of Neenchelys andamanensis sp. nov., holotype, PMBC 25065. IMT intermaxillary teeth, IO infraorbital pores, LL lateral-line pores, POM preoperculomandibular pores, SO supraorbital pores, ST supratemporal pores, UJT upper-jaw teeth, VT vomerine teeth. Arrows indicate interorbital and median supratemporal pores.

FIGURE 3. Lateral view of anterior nostril of Neenchelys andamanensis sp. nov., holotype. PMBC 25065 (right side). IO infraorbital pore, SO supraorbital pore. Arrow indicates an elongate flap.