Apterichtus malabar, 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 : 67-69

Apterichtus malabar n. sp.

Figures 11–12 , Tables 1 , 4

Holotype. AMS I.19426-001, 414 mm, female, Australia, New South Wales, off Malabar (33°58’S, 151°17’E), Sta. 3 Malabar Benthic Survey, 66 m, 26 March 1973.

Paratypes. 3 specimens, 240–363 mm. AMS I.19427-001, 240 mm, Australia, New South Wales, off Malabar (33°58’S, 151°17’E), 44–46 m, collected by benthic trawl, 14 March 1973. AMS I.19428-001, 343 mm, Australia, New South Wales, off Malabar (33°58’S, 151°17’E), Sta. 16, 49– 55 m, collected by D. Hoese using a benthic trawl, 2 January 1973. CAS 234253 (previously AMS I.19428-002), 363 mm, collected with AMS I.19428-001.

Diagnosis. An elongate species with: tail 1.9–2.2, head 18–19, and body depth 52–77 in total length; 3 preopercular pores and 5 pores in supratemporal canal; teeth conical, uniserial on jaws and vomer; 6 vomerine teeth; body mostly pale in preservative; and MVF 78–158, total vertebrae 155–162 (n=4).

Counts and measurements (in mm) of the holotype. Total length 414; head 23.4; trunk 174.6; tail 216; body depth at gill openings ~6.7; body width at gill openings ~4.9; body depth at anus ~5.0; body width at anus ~4.9; head depth at branchial basket 6.9; head width at branchial basket 6.5; snout length 4.1; tip of snout to rictus 7.4; tip of snout to tip of lower jaw 3.6; eye diameter 1.8; interorbital distance 2.0; gill-opening length 2.9; isthmus width ~1. Vertebral formula 73–155. Lateral-line pores difficult to count accurately due to small size and waxy exudate, 6 pores in branchial region.

Description. Body elongate, nearly cylindrical throughout, snout and tail tip sharply pointed; depth at gill openings 52–77 in TL. Branchial basket slightly wider and deeper than body. Head and trunk 1.8–2.1 in TL; head 18–19 in TL, 7.5–9.0 in trunk. Snout pointed, its underside somewhat rounded and bisected by a groove ( Figs. 11–12 ). Lower jaw included, its tip slightly in advance of eye. Slope of dorsal surface of snout approximately 40° relative to underside of snout. Lower jaw included, its tip slightly in advance of eye; snout extends beyond tip of lower jaw by slightly less 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, 4.1–5.5 in upper jaw and 13–17 in head, its anterior margin above tip of lower jaw, its center well in advance of 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. 11 ) small but apparent. Single median interorbital and temporal pores. Supraorbital pores 1+4, infraorbital pores 5+2 (holotype has 6+2 left), 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 pores in branchial region.

Teeth ( Fig. 12 ) uniserial, small, conical and slightly recurved. Intermaxillary with a chevron of 7 teeth (the largest in the jaw), followed by a short gap and a linear row of 6 small vomerine teeth. Jaw teeth nearly subequal, small, 17–18 teeth in each side of upper jaw and 18–19 teeth in each side of lower jaw, the posteriormost 6–7 irregularly biserial.

Body mostly colorless (presumably faded) in isopropanol.

Size. The largest specimen examined is 414 mm, a gravid female (ova 0.8–1.1 m diameter).

Etymology. Named malabar , in reference to its location of capture, to be treated as a noun in apposition.

Distribution. Known only from the type specimens which were captured off Malabar , NSW, Australia, at 44–66 m depth.

Remarks. As explained in the previous description of Apterichtus dunalailai , A. malabar shares the cephalic pore configuration of 5 supratemporal pores and 3 preopercular pores with A. dunalailai , A. klazingai and A. moseri . It differs significantly from all but A. dunalailai in having more total vertebrae (160 vs. 131–145). Apterichtus malabar is most similar to the deep water A. dunalailai but differs in having a shorter head (5.2–5.6% vs. 6.0–6.2% of TL), a shorter and deeper snout (19.8–21.2% vs. 17.5–20.4% of HL) (compare figures 6 and 11), and more preanal vertebrae (73–80 vs. 68–74).

It is notable that eastern Australia also has Apterichtus flavicaudus and A. klazingai in its shallow water ichthyofauna, generally occurring at overlapping depths.

Figures

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.

Tables

TABLE 4. Counts and proportions (in thousandths) of the holotype and 3 paratypes of Apterichtus malabar n. sp. TL = total length. HL = head length.

	holotype	mean	range
TL (mm)	414	---	240–414
HL/TL	56	54	52–56
Head and trunk/TL	478	515	478–543
Tail/TL	522	485	457–522
Upper jaw/HL	316	344	316–381
Snout/HL	175	188	175–204
Eye/HL	77	72	59–77
Interorbital/HL	85	84	74–88
Gill opening/HL	124	98	88–124
Isthmus/HL	47	52	47–56
Depth at gill opening/TL	16	16	13–19
Width/depth at gill opening	731	831	731–960
Preanal vertebrae	73	78	73–80
Total vertebrae	155	158	155–162