Ophichthus hirritus, E, John, 2010

E, John, 2010, Deepwater Indo-Pacific species of the snake-eel genus Ophichthus (Anguilliformes: Ophichthidae), with the description of nine new species, Zootaxa 2505, pp. 1-39 : 16-17

Ophichthus hirritus sp. nov.

Figures 16–18 , Table 2

Holotype. MNHN 1989-0747, 518 mm, female with developed ova, from Seychelle Is. (04o21'S, 56o19'E), captured by trap in 600 m by A. Intes on 22 Oct. 1987.

Paratypes. CAS 229178 (originally MNHN 1989-0747), 534 mm, female with developed ova, collected with the holotype; MNHN 1989-0749, 528 mm, mature male, from Seychelle Is. (04o34'S, 56o26'E), captured by trap in 600 m by A. Intes on 22 Oct. 1987.

Diagnosis. A moderately elongate, slender species of Ophichthus , subgenus Coecilophis , with: tail 58– 59% and head 7.9–8.4% of total length; dorsal-fin origin 3 pectoral-fin lengths behind gill opening; pectoral fins rounded; posterior nostril a hole in upper lip covered by a flap; head pores inconspicuous, SO 1+4, IO 4+2, POM 3+5; teeth conical, stout and numerous, not enlarged, biserial anteriorly and uniserial posteriorly on vomer, biserial on maxillary and biserial anteriorly on mandible; coloration uniform brown, paler ventrally, fins pale. Mean vertebral formula 19/62/171, total vertebrae 171–172 (n=3).

Counts and measurements (in mm) of the holotype. Total length 518; head 40.9; trunk 173.1; tail 304; predorsal distance 73; pectoral-fin length 9.1; pectoral-fin base 3; body depth at gill openings ~13.5; body width at gill openings ~12; body depth at anus ~13; body width at anus ~11.5; snout 6.7; tip of snout to rictus 12.1; eye diameter 4.7; interorbital distance 4.7; gill-opening height ~4.5; isthmus width ~8. Vertebral formula 19/63/172.

Description. Body moderately elongate ( Figure 16 ), compressed throughout, depth at gill openings 33–38 in TL. Branchial basket slightly wider and deeper than body. Head and trunk short 2.3–2.4 in TL; head 11.9– 12.6 in TL, 4.0– 4.2 in trunk. Snout rounded when viewed from above. Snout bisected on underside by a groove flanking anteriormost tooth. Lower jaw included; jaws slightly hooked such that jaw teeth are exposed and lips do not meet when mouth is closed. Mouth not elongate, rictus about one-half eye length behind rear margin of eye. Eye 3.2–3.5 in upper jaw and 10.5–10.7 in head, its center well behind middle of upper jaw. Tube of anterior nostril short, hardly capable of being deflected forward. Lips without barbels. Posterior nostril a hole above upper lip, entirely covered by a flap that does not extend to edge of mouth. Dorsal-fin origin approximately 3 pectoral-fin lengths behind gill opening. Median fins low. Pectoral fins rounded, less than jaw in length. Pectoral-fin base in upper half of gill opening.

Head pores ( Figure 17 ) small, inconspicuous. Single median interorbital and temporal pores. Supraorbital pores 1+4, infraorbital pores 4+2, lower jaw pores 5, preopercular pores 3. Lateral-line pores present but difficult to discern.

Teeth ( Figure 18 ) stout, conical, and numerous, not enlarged. Intermaxillary with a rosette of 7–9 teeth surrounding a central tooth, followed by 3, then 2 pairs, then a nearly uniserial row of 15 vomerine teeth descending in size. Maxillary dentition irregularly biserial comprising 18–20 pairs. Mandibular teeth close set, an irregular row of 3–5 teeth followed by 15–17 uniserial teeth. Larger paratype has irregularly triserial teeth in jaws and on vomer, rather than the more regular biserial and uniserial dentition of the holotype and smaller paratype.

Color in ethanol uniform brown, paler on tip of chin, throat and belly. Anterior nostrils pale. Lips with a faint brown edging along posterior half. All fins pale. A large indistinct white spot surrounds anus. Peritoneum pale.

Size. Largest known is a 530 mm female with developed ova.

Etymology. From the Latin hirritus , to snarl like a dog, in reference to its facial appearance.

Distribution. Known from three specimens trapped in 600 m off the Seychelle Islands.

Remarks. The new species is most similar to Ophichthus serpentinus Seale (1917) but differs in having a longer head (11.9–12.6 vs. 14.7–15.6 in TL), a slightly more posterior dorsal-fin origin, slightly more total vertebrae (171–172 vs. 162–167), and in having 3 rather than 2 preopercular pores. The new species differs from many of its deepwater congeners in having a rounded pectoral fin, a short upper jaw, a posterior eye location relative to the rictus, and in that its anal-fin base is pale rather than darkened posteriorly.

Figures

FIGURE 16. Holotype of Ophichthus hirritus, MNHN 1989 - 0747, 518 mm, from Seychelle Islands.

FIGURE 17. Head of holotype of Ophichthus hirritus, MNHN 1989 - 0747, 518 mm.

FIGURE 18. Dentition of holotype of Ophichthus hirritus, MNHN 1989 - 0747, 518 mm.

Tables

TABLE 2. Counts and proportions (in thousandths) of the holotype and two paratypes of Ophichthus hirritus sp. nov. TL = total length. HL = head length.

TL (mm)	Mean ---	Range 518–534
HL/TL	81	79–84
Head and trunk/TL Tail/TL	416 584	412–422 578–588
Depth at gill opening/TL	27	26–29
Dorsal-fin origin/TL Pectoral-fin length/HL	147 241	139–161 219–283
Upper jaw/HL	312	296–335
Snout/HL Eye/HL	201 94	164–225 93–95
Predorsal vertebrae	19	18–21
Preanal vertebrae Total vertebrae	62 171	61–63 171–172