Eustomias longibarba Parr 1927

Eustomias longibarba Parr, 1927

Eustomias longibarbus Parr, 1927:64, 65 [2 specimens, no holotype designated; fig. 34, heads of both specimens; fig. 35, lateral view; fig. 36B, barbel].—Fowler, 1936:1179 [compiled].

Eustomias longibarba.—Regan and Trewavas, 1930:86, 87 [4 additional specimens; E. microephalus Parr a probable synonym].—Beebe and Crane, 1939:212 [no additional specimens; types of longibarba and microcephalus examined; agree with Regan and Trewavas, 1930].—Morrow and Gibbs, 1964:413–415 [part, syntype of longibarba and holotype of microcephalus only; 2 additional eastern-Pacific specimens, 1 identified here as E. perplexus, the other not identifiable].—Badcock, 1970:1036 [1 specimen, off Fuertaventura, Canary Islands].—Gibbs, 1971:240 [2 specimens, off Bermuda].—Rass, 1971:511 [listed for Caribbean Sea].—Bekker et al., 1975:304 [1 specimen, 19°51′N, 76°43′W].

?Eustomias microcephalus Parr, 1927:75, 76 [holotype only, a juvenile not fully developed].

DIAGNOSIS.—A single terminal bulb 1.1%–2.3% SL, its length more than twice its width, with a single, digitate terminal projection 12%–90% of bulb length. Bulb and projection combined 1.9%–3.0% SL. Barbel 40%–78% SL, mostly more than 50%. Axis of stem moderately to darkly pigmented. External chevron-shaped or roundish striated areas unpigmented, closely spaced or contiguous distally. A few tiny spheres outside axis proximal to bulb in some specimens; otherwise no spherical or granular inclusions in stem. Middorsal paired spots between occiput and dorsal-fin origin usually 8, occasionally 9.

DESCRIPTION.—In a 68 mm specimen, the barbel is only 46% SL and is presumably still in the stage of rapid growth during transformation. In the others, barbel length is 52%–78% SL and does not change relative to SL with growth. The stem axis is moderately to darkly pigmented, usually becoming lighter distally, and pigment may be lacking immediately proximal to the bulb. The terminal projection from the bulb is unpigmented. The external chevron-shaped or roundish striated areas on the stem are unpigmented in all specimens except 1, in which they are pigmented in the proximal two-thirds of the stem. These areas become crowded distally, being contiguous just before the bulb. Very small spheres are often, but not always, present outside the stem axis in the region just proximal to the bulb. When present they are few and rather widely spaced. The bulb may be rather bulky or quite slender. It is 3–6 times as long as its greatest width (rarely less) and may be parallel-sided or slightly to considerably wider distally than proximally. The terminal projection has prominent spheres, at least in its basal portion. Its distal end, however, is often occupied by an apparently solid mass of opaque tissue. The lengths of the bulb and its terminal projection and the sexual dimorphism in these characters differ in specimens from the subtropical North Atlantic (Bermuda to Madeira and the Canary Islands) from those in the tropical Atlantic (Bahamas, Gulf of Mexico, Caribbean Sea, western tropical North and South Atlantic). We have examined 9 subtropical specimens: 1 female (106 mm), 6 males (99–129 mm), and 2 small ones (60–68 mm) of undetermined sex and 16 tropical specimens: 9 females (86–188 mm), 6 males (87–156 mm), and 1 of undetermined sex (81 mm). The subtropical population appears to be sexually dimorphic in bulb size and length of terminal projection, while there is little or no sexual dimorphism in these structures in the tropical population. The tropical population and females and some young of the subtropical population have larger bulbs but shorter terminal projections than males and some young of the subtropical population.

The bulb is larger relative to SL in tropical specimens than in subtropical males and some subtropical young (Figure 37). In the tropical specimens, the bulb is 1.4% SL in the largest specimen, 1.6%–2.3% in the others. In subtropical specimens, the bulbs of the smallest (60 mm) specimen and the only female are 1.8% SL, resembling the tropical specimens; in males the bulbs are smaller, 1.2%–1.6% SL. Change relative to SL with growth is little or none in either area at sizes up to 129 mm, but the 2 large tropical specimens (1.4%–1.7% SL) suggest a decrease relative to SL at larger sizes, at least in that area.

The terminal projection is smaller relative to SL in tropical specimens than in subtropical males and some subtropical young. It appears to decrease relative to SL in both groups. In tropical specimens the projection is 0.2%–1.0% SL. In subtropical specimens, the projection is 0.8% SL in the smallest (60 mm) specimen and 0.6% in the only female, resembling the tropical specimens; in a 69 mm subtropical specimen, it is 1.3%, and in the 6 males (99–129 mm) 0.8%–1.1%, all relatively longer at any size than in the tropical specimens (Figure 38). All subtropical specimens except the smallest (60 mm) and the female have projections 62%–90% of bulb length; in all tropical specimens the projection is 13%–50% of bulb length (Figure 39).

The combined length of bulb and projection decreases relative to SL in tropical specimens from 2.6%–3.0% at 81–90 mm to 1.9%–2.1% in the 2 largest specimens (156–188 mm). Subtropical specimens follow this regression, from 2.7%–2.8% at 60–68 mm, to 2.0%–2.6% at 121–129 mm.

The few recorded bulb colors may also be indicative of population differences. Parr (1927) described the bulb of 1 or both type specimens (tropical) as roseous (he did not indicate whether the specimens were fresh or preserved). In 2 mid-North Atlantic specimens (subtropical), a 111.5 mm male had the bulb and the inclusions in the projection mostly yellowish green, with orange-red areas in the middle of the bulb and at the distal end of the projection, while a 105.6 mm female had a yellowish green bulb with a much paler tip. In an 83.2 mm female from south of the Canary Islands (also subtropical), the bulb was yellowish green and the projection was not colored.

Enlargement of the postorbital organ appears to have begun in an 89 mm male (1.1% SL, 38% of fleshy orbit), but in 3 others 90–112 mm, the organ is 0.7%–0.9% SL. Other males are 99–156 mm, with organs 1.2%–2.6% SL, 50%–91% of fleshy orbit.

SIMILAR SPECIES.—The South Atlantic species spherulifer very closely resembles longibarba, especially the subtropical population of the latter, in barbel dimensions. The only truly distinguishing character is the presence in spherulifer of prominent spheres and granules in the stem outside of the axis; these inclusions may be present in as much as half of the distal stem, being few, small, and widely spaced proximally, but becoming large and crowded distally. In longibarba some specimens have very small spheres just before the bulb, but these are much smaller than those of spherulifer and are never more than a few. One consequence of the difference in development of stem inclusions is that the closely spaced external striated areas proximal to the bulb are readily discernible in longibarba, but masked in spherulifer.

Unfortunately spheres or granules become obvious only at sizes larger than about 100 mm SL. Smaller specimens of these 2 species may be virtually impossible to distinguish except by geographic area of occurrence.

Three other species—mesostenus, perplexus, and curtatus—have single, slender bulbs (their length more than twice the width) that may have a terminal projection. With the exception of 2 specimens of perplexus (see the account of that species), both curtatus and perplexus have extremely short terminal projections—not more than 0.2 mm long and often barely developed—and specimens larger than 100 mm SL have shorter bulbs (maximum 1.3 mm; only in about one-third of the small specimens of longibarba and in none larger than 100 mm is it shorter than 1.4 mm). Furthermore, curtatus usually has a shorter barbel (maximum 53% SL; only in a few developing longibarba is it less than 52%). In mesostenus, the bulb is very long, but the terminal projection appears to be a wide extension of the transparent outer sheath of the bulb, with only a thin projection of the bulb within it; mesostenus has only 4 VAV photophores over the anal-fin base, compared to 6–8 in longibarba.

All other species with single terminal bulbs have terminal filaments that are longer than the projection of longibarba, and their terminal bulbs are less than twice as long as wide.

DISTRIBUTION.—Across the North Atlantic between 30° and 35°N from Bermuda to Madeira, and extending to south of the Canary Islands, Straits of Florida, northern Bahamas, Gulf of Mexico, Caribbean Sea; tropical western and central Atlantic from 13°N to 10°S (Figure 44). This species apparently does not occur in the southern portion of the North Atlantic Subtropical Region of Backus et al. (1977), except in its easternmost extent, and it has not been recorded from the eastern tropical Atlantic. In view of its occurrence in the tropical west Atlantic and the Caribbean Sea, its absence from the Lesser Antilles is inexplicable but apparently real, for the 1920–1922 Dana expeditions collected extensively there.

GEOGRAPHIC VARIATION.—The differences in bulb length, terminal-projection length, and bulb color between the population that occurs from Bermuda to Madeira and the Canaries and the remaining, tropical population have been described. There is evidence that suggests that the “tropical population” may consist of 2 populations, 1 in the Bahamas, Gulf of Mexico, and Caribbean Sea, another in the tropical western and central Atlantic to 10°S. The latter population attains the longest bulbs, and 4 of the 7 specimens have the shortest terminal projections relative to bulb length (13%–28% of bulb) (Figures 37–39).

MATERIAL EXAMINED (13 males, 10 females, 3 unsexed).—Lectotype: BOC 2037 (, 85.5), 24°00′N, 77°17′W, 0-~1820 m (6000 ft wire), 28 Feb 1927.

Paralectotype: BOC 2038 (?, 80.6), 23°49′N, 76°59′W, 0-~2120 m (7000 ft wire), 9 Mar 1927.

Non-types (Tropical): USNM 225161 (, 105), 28°58′N, 88° 18′W, 0-~991 m (545 fm), 27 Oct 1960. USNM 225162 (, 93.4), 07°43′N, 42°04′W, 0–100 m, 0045–0245, 23 Mar 1977. USNM 226790 (, 107.7), 04°08′N, 24°41′W, 0–600 m, 2225–2255, 1 Feb 1968. USNM 226791 (, 89.8), 09°43′S, 27°07′W, 0–100 m, 2045–2100, 5 Feb 1968. ISH 627/66 (, 155.8), 05°34′S, 26°58′W, 0–320 m, 2000–2315, 20 May 1966. ISH 742/68 (, 187.7), 04° 11′N, 24°39′W, 0–200 m, 2121–2136, 1 Feb 1968. ISH 941/68 (, 93.2) 04°43′S, 26°39′W, 0-~2000 m, 1155–1215, 4 Feb 1968. ZMUC P202723 (, 114.9), 18°50′N, 79°07′W, 0-~1000 m (2000 mw), 0630, 29 Jan 1922. BMNH 1929.7.6.107 (, 97.2), 24°05′N, 74°36′W, 0-~150 m (300 mw), 2000, 14 Feb 1922. MCZ 56605 (, 106.4), 12°58′N, 73°34′W, 0–120 m, 0030–0505, 29 May 1966. UMML uncat. (, 101.5), 12°32′N, 50°03′W, 0–5020 m, 0846–1010, 5 Aug 1973. UMML uncat. (, 86.0), 17°43′N, 76°35′W, 0–80 m, 2105–2206, 4 Jul 1970. IOAN uncat. (, 89.7), 0–150 m, 29 Apr 1962. IOAN uncat. (, 86.8), 19°54′N, 76°38′W, 0–1500 m, 24 Mar 1973.

Non-types (Subtropical): USNM 225158 (2, 118.9, 129), 32°13′N, 64°16′W, 0–950 m, 0810–1053, 24 Aug 1971. USNM 225159 (, 113.2), 32°00′N, 64°23′W, 175 m, 0105–0205, 4 Sep 1968. USNM 225160 (, 98.7), 31°49′N, 64°18′W, 0–360 m, 1900–2005, 3 Sep 1968. ISH 78/66 (, 121.1), 33°45′N, 16°00′W, 0–600 m, 2110–2225, 10 May 1966. ISH 324/68 (, 83.2), 26°10′N, 19°26′W, 0–500 m, 22 Jan 1968. ISH 3196/79 (, 105.6), 34°21′N, 35°29′W, 0–1300 m, 1600–1852, 28 Apr 1979. ISH 3197/79 (, 111.5), 30°43′N, 46°16′W, 0–2000 m, 1600–1820, 25 Apr 1979. ZMUC P202722 (?, 68.3), 32°55′N, 21°51′W, 0-~250 m (500 mw), 1815, 20 Oct 1921. BMNH 1929.7.6.106 (?, 59.8), 31°59′N, 59°52′W, 0-~55 m (110 mw).