Ophichthus mccoskeri, Sumod & Hibino & Manjabrayakath & Sanjeevan, 2019

Sumod, K. S., Hibino, Yusuke, Manjabrayakath, Hashim & Sanjeevan, V. N., 2019, Description of a new species of deep-water snake eel, Ophichthus mccoskeri (Ophichthidae: Ophichthinae) from Andaman Sea, India, Zootaxa 4686 (1), pp. 112-118 : 113-114

Ophichthus mccoskeri sp. nov.

Proposed common name: Black-tipped Andaman Snake eel, with reference to the colouration and type locality at which the specimens were collected.

( Figures 1–4 , Table 1 )

Holotype. CMLRE IO /SS/FIS/00449 A (346 mm TL), 321 m off South Great Nicobar , India (6°38’18” N; 93°41’4.81” E) collected on September 2010 onboard FORV Sagar Sampada.

Paratypes. Five specimens (331–415 mm TL) CMLRE IO /SS/FIS/00449 A, CMLRE IO /SS/FIS/00449 B, off South Great Nicobar (6°37’48.84”N; 93°41’11.47”E) ; CMLRE IO /SS/FIS/00449 C, West Little Andaman (10°51’32.21”N; 92°21’54.54”E) ; CMLRE IO /SS/FIS/00449 D, off South Nicobar (6°35’53.1”N; 93°11’12.01”E) & CMLRE IO /SS/FIS/00449 E, off North Andaman (12°29’53.11.98”N; 93°10’12.20”E); collected from a depth ranging from 314–363 m onboard FORV Sagar Sampada .

Diagnosis. A moderately elongate species of the genus Ophichthus , subgenus Coecilophis , with the following combination of characters: head 13.0–14.0%, tail 54.6–56.8 %, depth at gill opening 4.0–4.7 % and dorsal-fin origin 18.4–20.5 % of total length; eyes large, its diameter almost equal to snout; pectoral fins elongate but not lanceolate, with elongated middle most ray; rear margin of orbit in advance of rictus, with its center positioned after the midpoint of upper jaw; posterior nostril opens along upper lip, with a small anterior flap; preoperculomandibular pores 3 + 6; teeth numerous, small and conical, biserial on maxillary with triserial ending, uniserial anteriorly and biserial posteriorly on mandible with triserial ending, and biserial anteriorly and uniserial posteriorly on vomer; colouration pale brown on dorsal surface and whitish below, snout tip brown with lower jaw pale; median fins and pectoral fins colourless except anal-fin base blackened posteriorly and vertebral formula 20/55/153.

Description. Counts and measurements of the holotype (in mm): Total length 346; head 48.6; trunk 106; tail 191; predorsal distance 69.0; pectoral fin length 15.8; pectoral fin base 4.6; body depth at gill opening 16.2; body width at gill opening 12.4; body depth at anus 11.8; body width at anus 10.3; snout length 9.5; upper jaw length 21.3; lower jaw length 20.6; eye diameter 9.0; interorbital width 5.6; gill opening height 8.1; inter-gill width 10.2; vertebral count 19/53/150.

Body ( Fig. 1 ) moderately elongate, cylindrical anteriorly and compressed in posterior tail region. Depth at gill opening 4.0–4.7% in total length. Head and trunk 44.2–45.4%, head 13.0–14.0% and tail 54.6–56.8% in total length. Snout tip moderately rounded and not elongated. Anterior nostril tubular, directed anteriorly, not reaching the snout tip. Snout not bisected on underside by a groove. Posterior nostril opens along upper lip with a short anterior flap, extends beyond the edge of lip. Upper jaw slightly extended at its tip, upper and lower lips meets when mouth is closed. Eye large, approximately equal to snout, 17.1–19.4% of head length. Posterior margin of eye in advance of rictus. Center of eye placed slightly posterior to middle of upper jaw. Branchial basket slightly wider and deeper than body. Dorsal-fin origin 18.4–20.5% in total length. Dorsal and anal fins placed in a groove for their entire length. Dorsal and anal fins end before the tail tip by approximately half the snout length. Pectoral fin elongated but not lanceolate, its base positioned in upper half of the gill opening.

Head pores ( Fig. 2 ) small but conspicuous. Single median interorbital and temporal pores, supraorbital pores (SO) 1 + 4, infraorbital pores (IO) 4 + 2, preoperculomandibular pores (POM) 3 + 6, supratemporal pores (ST) 3. Lateral-line pores before pectoral base 9–11, before dorsal-fin 20–21, before anus 54–59 (10, 21 and 56 in holotype).

Teeth ( Fig. 3 ) small, conical, and numerous. Intermaxillary with a rosette of 6–9 teeth preceded by 4–6 teeth, followed by 2–7 biserial vomerine teeth continued by 15–17 uniserial teeth. Biserial maxillary teeth with triserial ending. Mandibular teeth uniserial anteriorly with few isolated pairs, biserial in last quarter and ending as triserial.

Body colouration when fresh light brown on dorsal surface and white ventrally, including lower jaw and branchial region; dorsal surface of the head and snout brown; posterior and anterior nostrils pale; median and pectoral fins pale white, except posterior region of anal- fin base which is black ( Fig. 4 ). Colour after preservation in formaldehyde is darker brown dorsally, the remainder the same as in fresh specimens.

Distribution. Known only from the continental slope off Andaman waters, India (South Great Nicobar and West Little Andaman), depth ranging from 314– 363 m.

Etymology. This species is named in honor of the well-known snake eel expert John E. McCosker for his immense contributions to ophichthid eel systematics and phylogeny.

Figures

FIGURE 1. Fresh specimen of Ophichthus mccoskeri sp. nov., paratype, CMLRE IO/SS/FIS/0049 E, 447 mm TL.

FIGURE 2. Head of holotype of Ophichthus mccoskeri sp. nov., CMLRE IO/SS/FIS/00449 A, 346 mm TL.

FIGURE 3. Dentition of holotype of Ophichthus mccoskeri sp. nov., CMLRE IO/SS/FIS/00449A, 346 mm TL. A) Upper jaw B) Lower Jaw.

FIGURE 4. Enlarged view of posterior region of tail, holotype of Ophichthus mccoskeri sp. nov., CMLRE IO/SS/FIS/00449 A, 346 mm TL.