Ophichthus tomioi, 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 : 32-36

Ophichthus tomioi sp. nov.

Figures 32–35 , Table 4

Holotype. CAS 214208, 390 mm, immature male, from San Bernadino Strait, Philippine Islands, (12o54'29"N, 124o23'36"E), Field no. TI-95-3, captured by 30 m otter trawl in 376–382 m by Tomio Iwamoto at 1623–1819 hrs on 23 Sept. 1995.

Paratypes. MNHN 2001-1060, 369 mm, female, from Nuku Hiva (08o27'S, 140o10'W), Marquesas, Polynesia, station CP 1175, captured by beam trawl in 300 m by the MUSORSTOM 9 Expedition on 25 Aug. 1997. CAS 229180, 334 mm, an immature male, collected along with MNHN 2001-1060. MNHN 2001-1065, 447 mm, male, from Somo-Somo Strait, Fiji (16o45'S, 179o59'W), Field no. CP 1395, captured by otter trawl in 423 m on 23 Feb. 1999. MNHN 1989-0748, 427 mm, female, Seychelle Islands, (04o22'S, 56o18'E), Sta. Radiale 2, collected by benthic trap in 400 m, by A. Intes in Oct. 1987.

Diagnosis. A moderately elongate species of Ophichthus , subgenus Coecilophis , with: tail 59–62.5% and head 9.1–10% of total length; dorsal-fin origin slightly in advance of end of pectoral filaments; pectoral fins pointed, elongate and filamentous; posterior nostril a hole in outer lip, covered by an anterior flap; eye large, nearly equal to snout; head pores minute, SO 1+4, IO 4+2, POM 2+6-7; teeth conical, small, and numerous, uniserial on vomer, regularly biserial and close set on maxillary and mandible; coloration yellow, tan along mid-flanks, hindmost ventral surface of tail black. Vertebral formula 16/62/169, total vertebrae 166–189 (n=5).

Counts and measurements (in mm) of the holotype. Total length 390; head 37.5; trunk 119.5; tail 233; predorsal distance 52; pectoral-fin length 17; pectoral-fin base 3.0; body depth at gill openings 12.5; body width at gill openings 11.5; body depth at anus 11.3; body width at anus 10.3; snout 7.3; tip of snout to rictus 16.4; eye diameter 6.0; interorbital distance 5.7; gill-opening height 5.2; isthmus width ~7. Vertebral formula 16/62/169.

Description. Body moderately elongate ( Figure 32 ), compressed in posterior tail region; depth at gill openings 25–31 in TL. Branchial basket slightly wider and deeper than body. Head and trunk short, 2.5–2.7 in TL; head 10–11 in TL, 3.0– 3.8 in trunk. Snout short, rounded when viewed from above. Snout not bisected on underside by a groove. Lower jaw slightly included, upper and lower lips almost meet when mouth is closed. Mouth not elongate, rictus about 1/2 eye length behind rear margin of eye. Eye large, 2.4–2.9 in upper jaw and 5.4–6.6 in head, its center above middle of upper jaw. Tube of anterior nostril short, not reaching snout tip or lip margin. Lips without a barbel between nostrils. Posterior nostril a hole above upper lip, partially covered anteriorly by a small flap that extends slightly beneath edge of lip. Dorsal-fin origin in advance of pectoral-fin tips. Dorsal fin low, in a groove for its entire length. Anal fin higher, in a groove similar to that of dorsal. Pectoral fins pointed, elongate, and filamentous, about equal to jaw in length. Pectoral-fin base in upper half of gill opening.

Head pores ( Figure 33 ) small, inconspicuous, difficult to discern. Single median interorbital and temporal pores. Supraorbital pores 1+4, infraorbital pores 4+2, lower jaw pores 6–7, preopercular pores 2. Lateral-line pores present but difficult to enumerate, 8 before gill opening. Total pores of a paratype (MNHN 2001-1065) 160, 62 before anus, last pore 33 mm before tail tip.

Teeth ( Figure 34–35 ) small, conical, numerous. Intermaxillary with a rosette of 5–9 small teeth, then 3–6 irregular pairs and a linear row of 16–19 teeth on the vomer, becoming slightly smaller posteriorly. Maxillary teeth biserial, close set. An inner row of about 30–40 begins behind level of posterior nostril origin, flanked by an outer row of about 30–45 slightly smaller teeth. Mandibular teeth close set, forming biserial rows of 50–60 teeth. (The number but not the condition of jaw teeth varies considerably between specimens.)

Color in ethanol yellow ventrally, becoming tan along mid-flanks, then paler dorsally. Brown along lateral midline, posterior tail region, snout, lateral edge of anterior nostrils, interorbital region, and shoulders. Chin, throat, fins, inside of mouth, and tail tip pale. Peritoneum gray, darker than exterior surface. Ventral surface of posteriormost tail region (~1 head length) black, including a black smudge on anal fin membrane.

Size. Largest known is 447 mm, a male.

Etymology. I take pleasure in naming the new species tomioi in honor of my friend and colleague Tomio Iwamoto, who captured the holotype.

Distribution. Known from the Philippines, the Marquesas, Fiji and the Seychelle Islands, captured by trap and trawl at 300–423 m depth.

Remarks. The new species is most closely related to those Coecilophis with biserial jaw dentition and two preopercular pores, viz. Ophichthus aniptocheilos , O. brachynotopterus , O. congroides , O. genie , O. kunaloa , and O. mystacinus . All but O. genie possess the black anal-fin base coloration posteriorly. The dorsal-fin origin of O. mystacinus (mid-trunk), O. brachynotopterus , and O. congroides (slightly behind pectoral-fin tips) is posterior to that of O. tomioi . From O. kunaloa the new species differs in the relative length of its eye to its jaw (2.0–2.7 vs. 3.6–4.2 in O. kunaloa ). Ophichthus aniptocheilos has fewer vertebrae (140 vs. 166–189) and is more darkly pigmented than O. tomioi .

Ophichthus tomioi is perhaps the most widely distributed of deepwater Indo-Pacific Coecilophis . As stated in the description, the number but not the condition of jaw teeth varies considerably between some of the specimens. For example, the anterior vomerine teeth of the Fijian specimen (MNHN 2001-1065) are neatly biserial, whereas the jaw teeth are irregularly biserial ( Figure 35 ). Those of the Philippine holotype ( Figure 34 ) are similar in size and number but not as neatly arranged. I do not find such differences to be significant. The broad range of vertebral numbers of the holotype and four paratypes is also somewhat perplexing. The vertebral formulae of those specimens are: Seychelles 16/60/166; Fiji 16/67/169; Philippines 16/62/169; and Marquesas 18/63/187 and 18/63/189. I am advised by D.G. Smith of the National Museum of Natural History (pers. comm.) that widely-dispersed species of Indo-Pacific eels occasionally possess endemic forms in the Marquesas. I accept that likelihood here, however lacking other morphometric or meristic characters for those specimens I am hesitant to recognize them as distinct.

Figures

FIGURE 32. Holotype of Ophichthus tomioi, CAS 214208, 390 mm, from the Philippines.

FIGURE 33. Head of holotype of Ophichthus tomioi, CAS 214208, 390 mm.

FIGURE 34. Dentition of holotype of Ophichthus tomioi, CAS 214208, 390 mm.

FIGURE 35. Dentition of paratype of Ophichthus tomioi, MNHN 2001 - 1065, 447 mm, from Fiji.

Tables

TABLE 4. Counts and proportions (in thousandths) of the holotype and four paratypes of Ophichthus tomioi sp. nov. TL = total length. HL = head length.

	Mean	Range
TL (mm) HL/TL	--- 94	334–447 91–100
Head and trunk/TL	394	374–407
Tail/TL Depth at gill opening/TL	606 35	592–626 32–40
Dorsal-fin origin/TL	133	126–138
Pectoral-fin length/HL Upper jaw/HL	447 408	396–455 378–438
Snout/HL	198	175–211
Eye/HL Predorsal vertebrae	171 17	152–185 16–18
Preanal vertebrae	63	60–67
Total vertebrae	178	166–189