Eustomias inconstans Gibbs, Clarke & Gomon 1983

View data on Catalog of Fishes here.

The barbel of E. inconstans is 52%–65% SL, apparently not changing with growth after 85 mm SL. The axis of the stem is variably darkly to lightly pigmented, often becoming lighter distally, and the pigment may be streaky or peppered. The axis of the filament is lightly to moderately pigmented proximally; in 1 large specimen, no pigment could be discerned. The external chevron-shaped or roundish striated areas on the stem are unpigmented in some specimens; in others they may be pigmented in the proximal half to three–fourths of the stem, in the middle portion only, or, rarely, distally.

There may be 1 or 2 terminal bulbs. The proximal bulb, in those specimens 146–157 mm SL where it is present, is spheroidal or oblatespheroidal and is small, 0.4%–0.7% SL, and contiguous with the distal bulb. The distal bulb is spheroidal to long–ovoid, widening distally in 1 specimen. It is 1.3%–2.1% SL, apparently not changing relative to SL with growth, and is 2.6–3.6 times the length of the proximal bulb, when the latter is present.

The terminal filament is 6.2%–9.2% SL at all sizes. It has very small bulblets that are difficult to discern.

The postorbital organ of large males (140–154 mm) varies from 1.4%–2.0% SL, 45%–82% of fleshy orbit length, and appears to increase relative to SL within this limited range. No color observations have been recorded.

Two continguous terminal bulbs or a single terminal bulb. Barbel 52%–65% SL. Terminal filament short, without branches, 3%–9% SL. Distal (or only) bulb 1.3%–2.1% SL, 2.6–3.6 times length of small proximal bulb, when the latter is present. Axis of stem and filament pigmented. External chevron-shaped or roundish striated areas on stem pigmented or unpigmented. Middorsal paired spots between occiput and dorsal-fin origin 8.

Known only from off Oahu, Hawaiian Islands.

Gibbs RH, Jr, Clarke TA, Gomon JR. 1983. Taxonomy and distribution of the stomioid fish genus Eustomias (Melanostomiidae), I: Subgenus Nominostomias. Smithsonian Contributions to Zoology 380:1–139.

To at least 164 mm SL.

Central North Pacific [west of O'ahu, Hawaiian Islands], 21°20'N, 158°20'W, depth 0-150 meters.

Holotype: USNM 223756.

Species either with 1 or 2 single terminal bulbs. Barbel 52-65% SL. Terminal filament short, without branches, 3-9% SL. Distal (or only) bulb 2.6-3.6 times length of small proximal bulb, when present. Axis of stem and filament pigmented. External chevron-shaped or rounded striated areas on stem pigmented or not. Middorsal paired spots between occiput and dorsal-fin 8 (Ref. 11333).

Dorsal soft rays (total): 25; Analsoft rays: 40; Vertebrae: 69

Mesopelagic (Ref. 58302).

Eustomias inconstans

Eustomias patulus.—Johnson and Rosenblatt, 1971:310 [part; specimen from Hugh M. Smith cruise 32, sta 47, now BPBM 26411].

DIAGNOSIS.—Two continguous terminal bulbs or a single terminal bulb. Barbel 52%–65% SL. Terminal filament short, without branches, 3%–9% SL. Distal (or only) bulb 1.3%–2.1% SL, 2.6–3.6 times length of small proximal bulb, when the latter is present. Axis of stem and filament pigmented. External chevron-shaped or roundish striated areas on stem pigmented or unpigmented. Middorsal paired spots between occiput and dorsal-fin origin 8.

DESCRIPTION.—The barbel of E. inconstans is 52%–65% SL, apparently not changing with growth after 85 mm SL. The axis of the stem is variably darkly to lightly pigmented, often becoming lighter distally, and the pigment may be streaky or peppered. The axis of the filament is lightly to moderately pigmented proximally; in 1 large specimen, no pigment could be discerned. The external chevron-shaped or roundish striated areas on the stem are unpigmented in some specimens; in others they may be pigmented in the proximal half to three-fourths of the stem, in the middle portion only, or, rarely, distally.

There may be 1 or 2 terminal bulbs. The proximal bulb, in those specimens 146–157 mm SL where it is present, is spheroidal or oblate-spheroidal and is small, 0.4%–0.7% SL, and contiguous with the distal bulb. The distal bulb is spheroidal to long-ovoid, widening distally in 1 specimen. It is 1.3%–2.1% SL, apparently not changing relative to SL with growth, and is 2.6–3.6 times the length of the proximal bulb, when the latter is present.

The terminal filament is 6.2%–9.2% SL at all sizes. It has very small bulblets that are difficult to discern.

The postorbital organ of large males (140–154 mm) varies from 1.4%–2.0% SL, 45%–82% of fleshy orbit length, and appears to increase relative to SL within this limited range.

No color observations have been recorded.

DESCRIPTION OF HOLOTYPE.—Female, 157.0 mm SL. D 25. A 40. P1 3. P2 7. IP 7. PV 33. VAV 18. OV 32. VAL 18. AC 19. IA 58. IC 77. OA 50. OC 69. VAV photophores over anal-fin base 8. Branchiostegal photophores 11. Premaxillary teeth 13 left, 16 right: from anterior to posterior, a moderate fixed tooth followed by a long space, a fixed fang followed by a moderate space, a short-to-long series of 1 fixed and 2 depressible teeth (2 fixed, 1 depressible on right), 1 fixed and 3 depressible teeth of similar size, and 4 small depressible teeth; on right side only, 3 more smaller depressible teeth. Maxilla with about 25 small, slanting, serra-like teeth. Mandibular teeth 15 left, 16 right: from anterior to posterior, a short fixed symphysial tooth (replacement tooth also well developed) followed by a moderate space, a fixed fang followed by a moderate space, a long depressible tooth, a short-to-long series of 1 fixed and 2 depressible teeth, a short fixed tooth, 2 moderate depressible teeth (the rear appears to be a replacement tooth), a short-to-long series of 3 small depressible teeth (4 on right), and 3 smaller depressible teeth. Vertebrae 69.

Measurements (in mm): Predorsal length 138.2, preanal length 116.7, prepelvic length 94.0, head length 20.1, barbel length 105.0, proximal-bulb length 0.7, distal-bulb length 2.5, filament length 13.5, snout length 8.4, fleshy orbit length 5.0, postorbital-organ length 0.7, lower-jaw length 16.0, upper-jaw length 15.0, depth behind head 12.0, greatest depth 15.2, caudal-peduncle depth 3.4, pectoral fin broken, pelvic-fin length 24.0, dorsal-base length 19.4, anal-base length 41.3, longest premaxillary tooth 3.1, longest mandibular tooth 2.0.

Barbel with proximal bulb spheroidal; distal bulb ovoid and much larger in all dimensions.

SIMILAR SPECIES.—Only E. appositus, from the western Pacific, also has 2 contiguous bulbs, but in that species the proximal bulb is larger than in those large (146–162 mm) inconstans that have it (1.0% SL vs. 0.4%–0.7% in inconstans), and the distal bulb is smaller (0.7%–1.3% vs. 1.3%–2.1% SL; 0.7–1.3 times the proximal-bulb length vs. 2.6–3.6 times in inconstans). Neither specimen of appositus has pigment on the axis of the filament, whereas in all except 1 faded specimen of inconstans such pigment is prominent.

Of the other species of Nominostomias with a single terminal bulb, only E. gibbsi may have a single, unbranched terminal filament. In gibbsi, however, the bulb has a prominent black cap covering its proximal end.

DISTRIBUTION.—Known only from off Oahu, Hawaiian Islands (Figure 40).