See data on Catalog of Fishes here.
Three specimens, 55–71 mm, have very short barbels, 5%–8% SL. Relative length increases rapidly in this size range, for the next shortest barbels are 16%–20% SL in a few specimens 67–83 mm SL. All others, including 1 of 55 mm and most in the 74–83 mm range, have barbels 21%–35% SL, with no change in relative length with further growth. The stem axis is usually moderately, sometimes only lightly peppered with melanophores. Sometimes this pigment becomes gradually darker distally, but usually the distal one–tenth is abruptly darker. One side of the spheroidal–to–ovoid bulb has very dark pigment, continuous with that of the stem axis but broader, and, distinctively, forking at the distal end of the bulb to continue along the axis of the pair of filaments that bears large bulblets.
The spheroidal terminal bulb is relatively the smallest of any Nominostomias species, being 0.4%–0.6% SL in specimens smaller than 100 mm and decreasing to 0.3%–0.5% at larger sizes.
The filaments of 5 small specimens, 55–71 mm, were not completely formed. In these, a dorsal and a ventral pair were elongating, while a central pair was represented by low, round protuberances; the longest of the filaments in these 3 specimens were 0.2–1.5 mm (2 were not measured). In the filaments with the large bulblets, a series of small colorless bulblets on 1 side of each pigmented axis contrast strongly against the black axis pigment between the filament origin and the bulblet; the filament and its branches beyond the large bulblet are unpigmented. The 2 other pairs of filaments are unpigmented. One pair, usually the longest of the 3, has no bulblets. The other pair, the shortest, has numerous small bulblets.
The postorbital organ of large males (124–139 mm) is 1.5%–1.7% SL, 56%–70% of fleshy orbit.
There are usually 9 or 10 pairs of dorsal spots under the skin between the occiput and the dorsal-fin origin. Two specimens had 7 and 8 pairs, respectively. According to Gibbs et al. (1983), the terminal bulb, the small bulblets in the proximal part of the filaments with large distal bulblets, and the entire long filament without bulblets (except for some short gaps) were reddish purple in a fresh South Atlantic specimen. No colors were present in the stem, the distal part (including the large bulblet) of the clubbed filament, or the slender filaments with closely spaced bulblets.
A single, very small terminal bulb (0.3%–0.6% SL). Barbel short, 20%–35% SL in specimens over 80 mm SL and some smaller ones, shorter in some developing specimens up to about 80 mm SL. Three pairs of short filaments (2.2%–6.8% SL, but 4 times (young) to 21 times longer than bulb). Each filament of 1 pair with a prominent, elongate distal bulblet that may be larger than the terminal bulb; 1 pair slender, with closely spaced very small bulblets; 1 pair simple, with few or no inclusions, and usually the longest. Axis of stem moderately pigmented, becoming darker before bulb and very dark over 1 side of bulb, where pigment forks and extends along axis of the pair of filaments with large bulblets. External chevron–shaped or roundish striated areas unpigmented. Nine or 10 (rarely 7 or 8) pairs of dorsal spots under skin between occiput and dorsal-fin origin.
An essentially equatorial species, bulbornatus is 1 of the most commonly caught species of Eustomias. It has been taken between 10°N and 15°S in the central and western Pacific and the Indian Ocean. Outside of these latitudes, it has been taken in the South China Sea, off southern Japan (the holotype), off the North West Cape of Australia and in the southeastern Atlantic just west and south of the Cape of Good Hope.
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.
Eustomias bulbornatus is a member of the subgenus Nominostomias Reagan and Trewavas (1930). The following description applies to all member of Nominostomias.
Three well-developed, free pectoral rays. Seven pelvic rays. Barbel with slender stem having little or no external pigment (axis often pigmented), no row of dark spots, and no branches proximal to the terminal bulbs (E. multifilis may have a few short filaments on the stem near the bulb). One or 2 relatively small terminal bulbs, the distalmost with a projection or filament of variable complexity (the projection almost indiscernible in a few species). No wide ventral body groove posterior to pectoral–fin base (a narrow, shallow groove observed in some specimens). Photophore and vertebral counts high. Photophores in ventral series (IC) 69–80 (seldom fewer than 72, species modes mostly 75–78), in lateral series (OC) 63–73 (seldom fewer than 66, species modes mostly 69–72), VAV and VAL 15–21 (seldom fewer than 16, species modes 17–18 and 18–19, respectively). Vertebrae in continuous series 64–71 (seldom fewer than 65, species modes mostly 67–69). No paired photophores in lateral series. Number of teeth high: premaxillary 11–20, mandibular 14–29 in large specimens (fewer in many specimens less than 100 mm SL).
Counts of fin-rays, photophores, vertebrae, and teeth are of little use in distinguishing most species of Nominostomias, for even those species that show modal differences overlap the ranges of most other species.
None of the body proportions examined by Gibbs et al. (1983) showed convincing differences among species of Nominostomias. Differences in size or relative–growth patterns appeared to characterize a number of species for which few specimens were measured, but these are believed to be artifacts of sampling. The cloud of points of species with abundant measurements usually encompassed those of species with few measurements, and in those abundant species, isometric growth is indicated for almost every body part once metamorphosis is complete. The only body measurement to indicate allometric growth is the least caudal-peduncle depth, which decreases relative to SL.
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 160 mm SL
Gwaja Shima, Japan, 30°22'00"N, 129°08'30"E, Albatross station 4918, depth 361 fathoms.
Holotype: USNM 150566.
