Eustomias austratlanticus Gibbs, Clarke & Gomon 1983

Two terminal bulbs separated by a long interspace (usually 2.8-3 times length of distal bulb). Barbel 8.1% SL in large specimens, short 27% SL in small specimens. Terminal filament short, 3.9-9.4% SL with 2 short branches together about 2 distal-bulb lengths from the bulb. Distal bulb 1.4-2.1 times length of proximal bulb. Axis of stem pigmented, lightly in small specimen, moderately dark in large ones. External chevron-shaped or roundish striated area on stem pigmented. Middorsal paired spots between occiput and dorsal-fin origin 8 in small specimens (Ref. 11333).

Dorsal soft rays (total): 27; Analsoft rays: 41; Vertebrae: 70

Eustomias austratlanticus

DIAGNOSIS.—Two terminal bulbs separated by a long interspace (2.8%–3.4% SL, 2.8–3.0 times distal-bulb length). Barbel long (81%–3.4% SL) in the large specimen, short (27% SL) in the small specimen. Terminal filament short, 3.9%–9.4% SL, with 2 short branches together about 2 distal-bulb lengths from the bulb. Distal bulb 1.4–2.1 times length of proximal bulb. Axis of stem pigmented, lightly in the small specimen, moderately darkly in the large specimen. External chevron-shaped or roundish striated areas on stem pigmented. Middorsal paired spots between occiput and dorsal-fin origin 8 (small specimen only).

DESCRIPTION.—Based on 2 specimens, 74 and 156 mm SL; proportions listed for small specimen followed by large specimen. In percent of SL: barbel length 27–81, filament length 3.9–9.4, proximal bulb 0.9–0.5, distal bulb 0.9–1.2, distance between bulbs 2.8–3.4. In percent of proximal bulb: distal bulb 140–211, distance between bulbs 420–589. In percent of distal bulb: distance between bulbs 300–279.

The postorbital organ of the 1 large male is 1.7% SL, 57% of fleshy orbit.

No color observations have been recorded.

DESCRIPTION OF HOLOTYPE.—Male, 156.3 mm SL. D 27. A 41. P1 3. P2 7. IP 7. PV 32. VAV 21. OV 32. VAL 22. AC 19. IA 60. IC 79. OA 54. OC 73. VAV photophores over anal-fin base 8. Branchiostegal photophores 12. Premaxillary teeth 17 left, 13 right: from anterior to posterior, a fixed long tooth followed by a long space, a fixed fang, a short-to-long series of 2 fixed and 2 depressible teeth (1 fixed, 2 depressible on right), a slightly graded series of 1 fixed tooth, 1 replacement tooth, and 3 depressible teeth—all intermediate in size (1 fixed, 3 depressible on right), and 6 small depressible teeth (2nd and 6th being replaced on right, 1st and 3rd on left). Maxilla with about 25 short, slanted, serra-like teeth. Mandibular teeth 22 left, 24 right: from anterior to posterior, a small fixed symphysial tooth followed by a moderate space, a fixed fang followed by a short space, a long depressible tooth (2 on right), a short-to-long series of 2 fixed and 2 depressible teeth, a short-to-long series of 2 fixed and 3 depressible teeth, a short-to-long series of 5 smaller depressible teeth, and a short-to-long series of 5 very small depressible teeth, the last being replaced (6 right, the 1st and last being replaced). Vertebrae 70.

Measurements (in mm): Predorsal length 131.1, preanal length 112.7, prepelvic length 84.1, head length 17.9, barbel length 126.5, proximal-bulb length 0.9, distal-bulb length 1.9, distance between bulbs 5.3, filament length 14.7, snout length 6.9, fleshy orbit length 4.6, postorbital-organ length 2.6, lower-jaw length 15.9, upper-jaw length 14.3, depth behind head (greatest depth) 10.5, caudal-peduncle depth 2.6, pectoral-fin length 20.4, pelvic-fin length 21.7, dorsal-base length 20.5, anal-base length 39.8, longest premaxillary tooth 2.9, longest mandibular tooth 1.9.

Barbel with proximal bulb spheroidal with flattened anterior and posterior ends, distal bulb ovoid.

SIMILAR SPECIES.—The most similar species is bibulbosus, which also has a long interspace between the terminal bulbs and rarely may have 2 short branches together on the terminal filament. In bibulbosus the terminal filament is longer (22%–33% of SL when intact, vs. less than 10%), and, in large specimens, the proximal bulb is larger (0.6%–1.5% of SL, vs. 0.5%; distal bulb 1.0–1.6 times length of proximal bulb vs. 2.1) (Figure 7), and the postorbital organ of males smaller (1.2%–1.4% of SL, 38%–50% of fleshy orbit at 112–132 mm, vs. 1.7% of SL, 57% of fleshy orbit at 156 mm SL).

Eustomias bituberatus also has 2 short branches near the base of the terminal filament, but the barbel is longer and the proximal bulb larger at all sizes (Figures 6 and 7), and the bulbs are separated by a shorter distance in large specimens (Figure 8).

Of the remaining species with relatively simple terminal filaments, only micraster has the bulbs separated by a long interspace, but that species has a group of short branches, some with swollen tips, near the distal bulb, and, in large specimens, the barbel is shorter than in austratlanticus, and the distal bulb is smaller than the proximal.

DISTRIBUTION.—Known only from 2 stations in the subtropical south Atlantic, 1 in the southwest, the other in the southeast (Figure 40).

ETYMOLOGY.—An adjective combining the Latin auster (south) plus atlanticus (after the ocean of the same name), austratlanticus refers to the occurrence of this species in the South Atlantic Ocean.

MATERIAL EXAMINED (1 male, 1 unsexed).—Holotype: ISH 1554/71 (, 156.3), 27°14′S, 02°56′E, 0–2000 m, 1922–2345, 1 Apr 1971.

Paratype: USNM 223777 (?, 74.2), 33°15′S, 39°01′W, 0–195 m, 0215–0253, 9 Apr 1971.