Ophichthus ishiyamorum, 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 : 22-24

Ophichthus ishiyamorum sp. nov.

Figures 22–25

Holotype. USNM 394260, 437 mm, mature male, Gulf of Aden, Somalia (10o51'40"N, 43o56'35"E), captured by shrimp trawl at 258–326 m on 6 Sept. 1986, Station 4, SOSC field number 860906.

Paratype. CAS 227329, 429 mm, mature male, Gulf of Aden, Somalia (10o55'22"N, 46o51'14"E), captured in a lobster pot at 400 m on 23 Aug. 1986, Station BAST 11–23, SOSC field number 860823.

Diagnosis. A stout species of Ophichthus , subgenus Coecilophis , with: tail 52–55% and head 14–15% of total length; dorsal-fin origin ahead of pectoral-fin tips; pectoral fins wedge-shaped; posterior nostril in upper lip, covered by a flap; head pores inconspicuous, SO 1+4, IO 4+2, POM 3+7–9; teeth small, conical, widely spaced, nearly uniserial on vomer and jaws; coloration uniform tan, fins pale. Mean vertebral formula 15/50/ 131, total vertebrae 130–132 (n=2).

Counts and measurements (in mm) of the holotype and those of the paratype (in parentheses). Total length 437 (429); head 63.5 (62.8); trunk 143.5 (132.2); tail 230 (234); predorsal distance 82.0 (82.5); pectoral-fin length 22.8 (22.4); pectoral-fin base 5.8 (5.5); body depth at gill openings ~20 (18); body width at gill openings 17; body depth at anus ~18 (~15); body width at anus ~13.5 (~15); snout 12.0 (11.6); tip of snout to rictus 18.7 (21.8); eye diameter 6.5 (6.5); interorbital distance 9.8 (8.7); gill-opening height ~9.5 (~9); isthmus width ~10 (~9). Vertebral formula 15/50/132 (15/49/130).

Description. Body stout ( Figure 22 ), compressed throughout, depth at gill openings 22–24 in TL. Branchial basket deeper and slightly wider than body. Head and trunk short, 2.1–2.2 in TL; head 6.8 in TL, 2– 2.3 in trunk. Snout short, broad, slightly swollen in appearance. Snout not bisected on underside by a groove. Jaws subequal. Lips meet when mouth is closed. Mouth moderately elongate, rictus about one-fourth eye length behind rear margin of eye. Eye 2.9–3.4 in upper jaw and 9.6–9.8 in head, its center behind middle of upper jaw. Tube of anterior nostril short, barely extending beyond lip of lower jaw. Posterior nostril a hole above upper lip, entirely covered by a flap that extends below edge of upper lip. Dorsal-fin origin slightly ahead of end of pectoral fin. Dorsal fin low, in a shallow groove. Anal fin low, in a groove similar to that of dorsal. Pectoral fins wedge-shaped, slightly longer than jaw in length. Pectoral-fin base in upper half of gill opening.

Head pores ( Figure 23 ) small, inconspicuous. Single median interorbital and temporal pores. Supraorbital pores 1+4, infraorbital pores 4+2, lower jaw pores 7–9, preopercular pores 3. Lateral-line pores present but difficult to discern. The anterior-most left mandibular pores of the paratype are abnormal in that a small pair exists just above and another just anterior to the anterior-most normal pair ( Figure 24). Ophichthid eels (and other eels) occasionally possess additional pores, however such an abnormality has not been reported from other ophichthids.

Teeth ( Figure 25 ) small, conical, sharp. Intermaxillary with a rosette of 5 small teeth, then 2 irregular pairs, and a linear row of 12 vomerine teeth, becoming smaller posteriorly. Maxillary dentition mostly uniserial, 14–15 widely spaced small teeth flanked by 3–4 larger teeth that begin behind level of posterior nostril. Mandibular teeth pointed, widely spaced, about 14–15 in a single row.

Color in ethanol tan, the result of minute brown punctations which overlay the entire body, more numerous and denser along dorsal midhalf. Dorsal-fin base dark in trunk region, its margin pale throughout. Nostrils pale. Fins pale. Base of anal fin in posterior region not darkened. Peritoneum unpigmented.

Size. Largest known specimen is 437 mm, a mature male.

Etymology. I am pleased to name this interesting eel in honor of Nelson and Patsy Ishiyama for their interest in and generous support of ichthyological research.

Distribution. Known only from the Gulf of Aden, Somalia, where it was trapped and trawled between 258– 400 m.

Remarks. The new species is most similar to Ophichthus urolophus in terms of its pectoral fin shape, body coloration, dentition, and vertebral number (total vertebrae 130–132 vs. 134–139). It differs from O. urolophus in its dorsal-fin origin, arising before the pectoral-fin tips rather than slightly behind them, and, as well, from all other Coecilophis in having the longest head length (14–15% of TL vs. 13% or less for all others).

Figures

FIGURE 22. Holotype of Ophichthus ishiyamorum, USNM 394260, 437 mm, from Somalia.

FIGURE 23. Head of holotype of Ophichthus ishiyamorum, USNM 394260, 437 mm.

FIGURE 25. Dentition of holotype of Ophichthus ishiyamorum, USNM 394260, 437 mm.