Ophichthus congroides, 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 : 12-15

Ophichthus congroides sp. nov.

Figures 13–15

Holotype. NMNZ P. 41177, 522 mm, an immature male, from Akiaki Island (18o33'S, 139o12'W), Tuamotu Islands, Polynesia, trapped in 300 m by J. Poupin on 10 June 1989.

Paratype. CAS 229328, 472 mm, an immature male, captured with the holotype.

Diagnosis. An elongate species of Ophichthus , subgenus Coecilophis , with: tail 60–63% and head 8.3– 8.4% of total length; dorsal-fin origin above mid-pectoral fin; pectoral fins elongate, lanceolate; posterior nostril opens within outer lip, with a small anterior flap; head pores small but apparent, SO 1+4, IO 4+2-3, POM 2+6; teeth small, conical and numerous, biserial anteriorly and uniserial posteriorly on vomer, biserial on maxillary and partially biserial on mandible; coloration uniform brown-gray, paler on ventral and dorsal surfaces, fins pale. Mean vertebral formula 21/76/206, total vertebrae 204–208 (n=2).

Counts and measurements (in mm) of the holotype and those of the paratype (in parentheses). Total length 522 (472); head 43.1 (39.6): trunk 163.9 (137.4); tail 315 (295); predorsal distance 72 (64); pectoral-fin length 18.3 (damaged); pectoral-fin base 3.9 (3.9); body depth ~14.2 (damaged) at gill openings; body width at gill openings ~10.6 (damaged); snout 8.5 (8.1); tip of snout to rictus 18.5 (17.6); eye diameter 7.7 (6.7); interorbital distance 6.9 (6.2); gill-opening height ~4 (~5); isthmus width ~6 (damaged). Vertebral formula 22/ 77/208 (20/75/204).

Description. Body elongate ( Figure 13 ), compressed in tail region, depth at gill openings 37 in TL. Branchial basket slightly wider and deeper than body. Head and trunk short, 2.5–2.7 in TL; head 11.9–12.0 in TL, 3.5–3.8 in trunk. Snout not elongate, nearly rounded when viewed from above. Snout not bisected on underside by a groove. Lower jaw included, upper and lower lips meet when mouth is closed. Mouth moderately elongate, rictus about one eye length behind rear margin of eye. Eye 2.4–2.6 in upper jaw and 5.6– 5.9 in head, its center slightly behind middle of upper jaw. Tube of anterior nostril very short, barely capable of being deflected forward. Lips without barbels. Posterior nostril a hole above upper lip, partially covered along anterior quarter by a minute flap. Dorsal-fin origin slightly above mid-pectoral fin. Median fins very low, in a groove that deepens posteriorly for its entire length. Pectoral fins pointed, dorsal-most rays elongate, nearly equal to jaw in length. Pectoral-fin base in upper half of gill opening.

Head pores ( Figure 14 ) small but apparent. Single median interorbital and temporal pores. Supraorbital pores 1+4, infraorbital pores 4+3 (paratype has 4+2), mandibular pores 6, preopercular pores 2. Lateral-line pores present but difficult to enumerate, 9 before gill opening, 78 before mid-anus.

Teeth ( Figure 15 ) minute, conical. Intermaxillary with a rosette of 6 small teeth, then 6 pairs of erect, pointed teeth, and a linear uniserial row of 11 smaller teeth on the vomer, becoming smaller posteriorly. Maxillary teeth irregularly biserial, an outer row of about 40 teeth flanked by an inner row of 32–33 teeth. Mandibular teeth irregularly biserial, an outer row of 38–40 close-set teeth flanked by an inner row 18–22 teeth.

Color in isopropanol tan, darker along mid-flanks. Throat region and posterior half of head gray. Belly region grayish-black. Fins pale, except dorsal which is dark about a head length before tail tip. Anterior nostrils, inside of mouth, and tail tip pale. Peritoneum black.

Size. The holotype, an immature male, is 522 mm.

Etymology. Named congroides because of the similarity of its posterior nostril condition to that of certain congrids.

Distribution. Known only from the type series, trapped in 300 m off Akiaki Island, Tuamotu Islands, Polynesia.

Remarks. The holotype of the new species is in excellent condition. The paratype has been eviscerated and its pectoral fins are damaged. There is some confusion as to the precise locality of their collection. The collector, Joseph Poupin, had set deep traps and had collected two Gymnothorax intesi , presumably along with the new species. He identified the new species as congrids and gave them, along with the morays, to John E. Randall of the Bishop Museum of Natural History. The eels were then loaned to Peter Castle of Victoria University of Wellington, and ultimately deposited at the Museum of New Zealand Te Papa Tongarewa. The paratype was subsequently deposited at the California Academy of Sciences.

The new species is most closely related to those species of the subgenus Coecilophis with elongate pectoral fins, two preopercular pores, and biserial maxillary and mandibular dentition, viz. O. aniptocheilos , O. brachynotopterus , O. genie , O. kunaloa , O. mystacinus and O. tomioi . It has more total vertebrae (204– 208) than all of those species, and its dorsal-fin origin (slightly in advance of the pectoral-fin tips) is significantly different than that of O. brachynotopterus and O. mystacinus , which arises in mid-trunk, and that of the other species which arises in advance of the pectoral-fin tips. It is similar to O. echeloides , O. genie , O. hirritus , O. humanni , O. microstictus , O. serpentinus , and O. urolophus in lacking black pigmentation along the posterior base of the anal fin.

Figures

FIGURE 13. Holotype of Ophichthus congroides, NMNZ P. 41177, 522 mm, from Tuamotu Islands.

FIGURE 14. Head of holotype of Ophichthus congroides, NMNZ P. 41177, 522 mm.

FIGURE 15. Dentition of holotype of Ophichthus congroides, NMNZ P. 41177, 522 mm.