Apterichtus dunalailai, Hibino, Yusuke, 2015

Hibino, Yusuke, 2015, A review of the finless snake eels of the genus Apterichtus (Anguilliformes: Ophichthidae), with the description of five new species, Zootaxa 3941 (1), pp. 49-78 : 57-58

Apterichtus dunalailai n. sp.

Figures 6–7 , Tables 1–2

Holotype. MNHN 1987-0810, 289 mm, male, Vanuatu (17o53'S, 168o28'E), depth 291–300 m, captured using Warren Dredge, Campaign MUSORSTOM 8-1994, Station DW 1015, collected by N. Alis, September 1994.

Paratypes. MNHN 1987-0811, 175+ mm (approximately 330 mm by extrapolation) (tail section missing, presumably cut by dredge), Vanuatu (17o53'S, 168o58'E), depth 360–450 m, captured using Warren Dredge, Campaign MUSORSTOM 8-1994, Station DW 1016, collected by N. Alis, September 1994. MNHN 2001-1092, 177 mm, Fiji, Yangusta Cluster (18o39'S, 178o26'E), depth 389–400 m, captured using Warren Dredge, Campaign Bordau I 1999, Station DW 1499, collected by N. Alis on 12 March 1999.

Diagnosis. An elongate species with: tail 1.8–2.0, head 16–17, and body depth 71 in total length; 3 preopercular pores and 5 pores in supratemporal canal; teeth conical, uniserial on jaws and vomer; 2–3 vomerine teeth; body mostly pale in preservative, a fine brown sparse speckling on body and tail; and MVF 70–160, total vertebrae 160 (n=3).

Counts and measurements (in mm) of the holotype. Total length 289; head 17.9; trunk 127; tail 144; body depth at gill openings ~4.2; body width at gill openings ~3.5; body depth at anus ~4; body width at anus ~4; head depth at branchial basket ~5.3; head width at branchial basket ~5.2; snout 3.8; tip of snout to rictus 5.8; tip of snout to tip of lower jaw 3.5; eye diameter 1.4; interorbital distance 1.4; gill-opening length 1.6; isthmus width ~0.7. Vertebral formula 74–160. Lateral-line pores difficult to count accurately due to small size and waxy exudate, 6 in branchial region.

Description. Body elongate, nearly cylindrical throughout, snout and tail tip sharply pointed, depth at gill openings 69–74 in TL. Branchial basket slightly wider and deeper than body. Head and trunk 2.0– 2.2 in TL; head 16.1–16.7 in TL, 6.4–7.1 in trunk. Snout sharply pointed, its underside slightly rounded and bisected by a groove ( Figs. 6–7 ). Slope of dorsal surface of snout approximately 25° relative to underside of snout. Lower jaw included, its tip slightly in advance of eye; snout extends beyond tip of lower jaw by more than lower jaw length; upper and lower lips meet when mouth is closed. Mouth moderately elongate. Rictus well behind rear margin of eye. An obvious crease extends posteriorly in upper lip from beneath eye to rictus. Eye moderately developed, 4.0– 4.5 in upper jaw and 12.8–13.7 in head, its anterior margin above middle of upper jaw. Anterior nostril within a tube, approximately one-third the diameter of the eye, its base in anterior third of snout and anterolaterally directed when viewed from above. Posterior nostril opens in outer lip beneath anterior margin of eye. Branchial openings low, ventral; branchial region modestly expanded, creating a bulbous region in posterior half of head.

Head pores ( Fig. 6 ) small but obvious. Single median interorbital and temporal pores. Supraorbital pores 1 + 4, infraorbital pores 5 + 2, supratemporal pores 5, lower jaw pores 4, preopercular pores 3. Lateral-line pores difficult to count accurately due to small size and waxy exudate, 6 in branchial region.

Teeth ( Fig. 7 ) uniserial, small, conical and slightly recurved. Intermaxillary with a chevron of 5 teeth (the largest in the jaw), followed by a short gap and a linear row of 2–3 small vomerine teeth. Jaw teeth nearly subequal, small, 17–18 teeth in each side of upper jaw and 18–20 teeth in each side of lower jaw.

Body mostly faded in alcohol preservative (preserved in formalin and transferred to alcohol more than 15 years ago), however body and tail are overlain with a sparse fine brown speckling.

Size. The largest intact specimen examined is 289 mm, a male.

Etymology. Named dunalailai , a “small eel” in Fijian, to be treated as a noun in apposition.

Distribution. Known from Vanuatu and Fiji, captured using a benthic dredge at 291–450 m depth.

holotype mean range Remarks. The new species differs from its congeners in the size and shape of its snout, its cephalic pore configuration, and in its vertebral numbers. Apterichtus dunalailai shares the cephalic pore configuration of 5 supratemporal pores and 3 preopercular pores with A. klazingai , A. malabar , and A. moseri . It differs significantly from all but A. malabar in having more total vertebrae (160 vs. 131–145). Apterichtus dunalailai is most closely related to the shallow water A. malabar but differs in having a longer head (6.0–6.2% vs. 5.2–5.6% of TL), a more slender snout (compare to Figs. 11 & 12 ), and fewer preanal vertebrae (68–74 vs. 73–80).

Figures

FIGURE 6. Head of holotype of Apterichtus dunalailai, MNHN 1987 - 0810, 289 mm. Drawn by Corlis Schneider.

FIGURE 7. Dentition of holotype of Apterichtus dunalailai, MNHN 1987 - 0810, 289 mm. Drawn by Corlis Schneider.

FIGURE 11. Head of holotype of Apterichtus malabar, AMS I. 19426 - 001, 414 mm. Drawn by Corlis Schneider.

FIGURE 12. Dentition of holotype of Apterichtus malabar, AMS I. 19426 - 001, 414 mm. Drawn by Corlis Schneider.