Comprehensive Description
provided by Smithsonian Contributions to Zoology
Eustomias bimargaritoides
Eustomias bibulbosus.—Clarke, 1974:344 [part; Hawaii area; bibulboides, bituberoides also included].
DIAGNOSIS.—Two terminal bulbs separated by a short interspace (1.1%–2.0% SL, 0.5–1.1 times length of distal bulb). Barbel length 44%–59% SL. Terminal filament long (21%–28% SL), with 2 long branches arising closely together at 6–11 distal-bulb lengths from the distal bulb (at all available sizes, 83–126 mm SL); all long branches with conspicuous closely spaced bulblets. Stem of filament with no bulblets and with 1–6 short, slender branches in its basal half. Barbel without melanophores (rarely very sparse on axis of stem). Paired middorsal spots under skin between occiput and dorsal-fin base, 8.
DESCRIPTION.—The barbel of bimargaritoides is 44%–59% SL, its growth apparently isometric in the observed size range (83–126 mm). In most specimens the barbel is entirely without melanophores. Three specimens have sparse, widely spaced melanophores along the stem axis, and 1 has some light, patchy external pigment near the bulb. None of these has pigment between the bulbs or in the filament. The external chevron-shaped or roundish striated aras are not pigmented.
The proximal bulb is variously spheroidal, ovoid, squarish, oblate, or lemon-shaped. The bulb appears to decrease relative to SL, from 1.2%–1.7% in specimens smaller than 100 mm to 1.0%–1.3% in the 2 largest (118 and 126 mm).
The distal bulb is ovoid and elongate, its width equal to or narrower than that of the proximal bulb. Distal-bulb length is 1.3%–2.1% SL, 1.0–1.3 times the proximal-bulb length, and does not appear to change relative to SL.
The distance between the bulbs is 1.1%–2.0% SL, 0.5–1.1 times the distal-bulb length, and also appears not to change relative to SL.
In all except 1 specimen, the terminal filament has 1–5 small, fairly widely spaced side branches proximally and 2 large branches arising together 6–11 distal-bulb lengths beyond the bulb. The long branches and main filament distal to the branching have prominent, closely spaced internal bulblets. The main filament is better developed than the branches and has more and larger bulblets and more secondary branches. There are no bulblets in the stem of the filament until just before the main branches arise.
Filament length is 21%–28% SL, 11–16 times the distal-bulb length, with no apparent change relative to SL.
The largest male (126 mm), which has well-developed testes, has a postorbital organ only 1.0 mm long (0.8% SL, 37% of fleshy orbit length). A 115 mm male with testes just beginning to enlarge has a 0.5 mm postorbital. Development of the organ in males apparently begins at a relatively large size, and it probably remains relatively small at larger SL.
No observations of barbel colors have been recorded.
DESCRIPTION OF HOLOTYPE.—Sex undetermined, 102.1 mm SL. D 25. A 38. P1 3. P2 7. IP 7. PV 34. VAV 17. OV 34. VAL 18. AC 19. IA 58. IC 77. OA 52. OC 71. VAV photophores over anal-fin base 6. Branchiostegal photophores 12. Premaxillary teeth 11 left, 14 right: from anterior to posterior, a long fixed tooth followed by a long space, a fixed fang followed by a moderate space, a short fixed tooth, 2 long depressible teeth (2nd longer than 1st), 2 short fixed teeth (2nd longer), a missing tooth, a short-to-long series of 3 moderate depressible teeth, and a short-to-long series of 3 small depressible teeth (on the left side 2 represented by spaces, but there is no place for a 3rd). Maxilla with 3 small erect teeth and about 17 short, slanted, closely spaced serra-like teeth. Mandibular teeth 17 left, 18 right: from anterior to posterior, a short fixed symphysial tooth followed by a wide space, a fixed fang followed by a wide space, a long depressible tooth, 2 short fixed teeth, a long depressible tooth, 2 short-to-long series of 3 depressible teeth, a short-to-moderate series of 4 depressible teeth, and 2 short depressible teeth. The missing teeth on the left side of both jaws are represented by spaces, some with attachment marks. Vertebrae 68 (the first only partially ossified).
Measurements (in mm): Predorsal length 85.4, preanal length 73.0, prepelvic length 55.3, head length 11.8, barbel length 53.1, proximal-bulb length 1.6, distal-bulb length 2.1, distance between bulbs 1.1, filament length 28.5, snout length 3.9, fleshy orbit length 2.8, postorbital-organ length 0.7, lower-jaw length 11.8, upper-jaw length 10.7, depth behind head (greatest depth) 7.0, caudal-peduncle least depth 1.9, pectoral-fin length 15.4, pelvic-fir length 16.0, dorsal-base length 14.1, anal-base length 26.2, longest premaxillary tooth 2.1, longest mandibular tooth 1.7.
Barbel with slightly oblate-spheroidal proximal bulb, long-ovoid distal bulb narrower than proximal bulb. Terminal filament with a short side branch 2.6 mm from distal bulb, 2 together at 4.4 mm; 2 long branches arise 16.8 mm from bulb, these and main filament with distal secondary branches.
SIMILAR SPECIES.—The North Atlantic E. bimargaritatus closely resembles bimargaritoides in having large branches arising well distad on the filament, but in bimargaritatus these branches arise closer to the bulb (1–5 distal-bulb lengths out except in a 200 mm specimen, in which they are 10 bulb lengths out) and have smaller, more widely spaced bulblets. The filament is shorter in bimargaritatus (16% SL or less, except in a 200 mm specimen, vs. 21%–28%); proximal to the long branches, tiny bulblets are present and short side branches are absent (1 exception); and the barbel tends to be longer (in specimens larger than 90 mm 58%–70% SL vs. 44%–59%). Eustomias arborifer, E. crossotus, and E. grandibulbus have branches arising closer to the bulb than in any bimargaritoides, and crossotus and grandibulbus have the stem axis well pigmented in all except the smallest specimens.
DISTRIBUTION.—Known from the North Pacific near the Hawaiian Islands and from the South Pacific near the Marquesas Islands (Figure 41).
ETYMOLOGY.—A Latin adjective from the species name, bimargaritatus (adorned with two pearls), plus the suffix -oides (resembling), bimargaritoides alludes to the similarity of the terminal barbel filaments of the 2 species.
MATERIAL EXAMINED (2 males, 4 females, 3 unsexed).—Holotype: SIO 71–296 (?, 102.1), 27°28′N, 155°26′W, 29 Sep 1971.
Paratypes: USNM 224094 (, 118), 21°20′N, 158°02′W, 0–810 m, 1045–1355, 14 Dec 1970. USNM 224096 (, 83), 21°20′N, 158°20′W, 0–350 m, 2245–0044, 26 May 1974. USNM 224097 (, 126.3), 07°52′S, 135°04′W, 0–176 m, 2006–2107, 21 Aug 1956. USNM 224098 (?, 103.7), 21°20′N, 158°20′W, 0–1200 m, 1122–1543, 4 Jul 1978. USNM 224099 (, 94), 06°33′S, 139°30′W, 0–337 m, 2010–2111, 22 Nov 1955. USNM 224100 (?, 83.5), 15°50′N, 158°00′W, 0–300 m, 0021–0215, 13 Jul 1979. BPBM 26413 (, 95), 20°59′N, 158°34′W, 0–122 m, 1952–0152, 25 Jul 1967.
Non-type: USNM 224095 (, 102), 21°20′N, 158°20′W, 0–1100 m, 0245–0600, 31 Aug 1973.
GROUP III
The species of this group have 2 terminal bulbs and 3 to many terminal filaments arising together from the distalmost bulb. In some species the filaments are simple and only about twice as long as the bulb; in others the filaments are very long and may have prominent bulblets or elongate inclusions. Nine species comprise this group. A synopsis of their salient characters is given in Table 4, and their barbel and postorbital-organ dimensions are plotted in Figures 22–25.
Eustomias melanostigma Regan and Trewavas, 1930
Eustomias melanostigma Regan and Trewavas, 1930:85 [2 syntypes, 17°43′ and 45′N, 64°56′W].—Morrow and Gibbs, 1964:417, 418 [part; melanonema in synonymy; no additional specimens].—Blache, Cadenat, and Stauch, 1970 [part; in key; no additional specimens].
Eustomias bibulbosus.—Parin and Pokhilskaya, 1974:353–355 [part, Vityaz sta 4921; examined by us].—Bekker et al., 1975:305 [part, sta 1256; examined by us].—Parin et al., 1977:101, 102 [part, Vityaz sta 7285; examined by us].
DIAGNOSIS.—Two terminal bulbs separated by a long distance (2.1%–4.1% SL, 1.7–3.8 times length of distal bulb in specimens larger than 70 mm SL). Barbel length 31%–82% SL except when developing. Three to 7 short terminal filaments (less than 10% SL), without prominent bulblets, arising together from distal bulb or from a short distal stem; 1 filament thicker and longer than the rest. Some or all filaments with pigmented axes. Distal bulb ovoid in shape, only slightly longer than wide, 1.0%–2.2% SL (smaller in some specimens less than 75 mm), 1.2–2.5 times proximal-bulb length. Sum of proximal- and distal-bulb lengths 2.7 mm or less. Axis of stem and between bulbs variably pigmented; a black spot or cap almost always formed at proximal end of distal bulb. External chevron-shaped or roundish striated areas on stem unpigmented. Middorsal paired spots between occiput and dorsal-fin origin 7 or 8, occasionally 9.
DESCRIPTION.—The barbel apparently grows very rapidly in small specimens, those 70–75 mm SL having barbels 31%–82% SL. The range at most larger sizes is 48%–80% and appears not to change relative to SL with growth. Almost all specimens have the axis of the stem peppered with melanophores, some lightly, others fairly darkly; there is a tendency for the portion just preceding the proximal bulb to become noticeably lighter. The external chevron-shaped or roundish areas are unpigmented. The axis between the bulbs is unpigmented or very sparsely pigmented proximally, becoming darkly pigmented distally in specimens smaller than about 100 mm: pigmentation in this area is relatively uniform in larger specimens. At the base of the distal bulb, pigmentation becomes very dark on 1 side of the axis to form a spot, or, usually, a partial cap that extends distad a short distance on the bulb. Two small Indo-Pacific specimens (58 and 81 mm) lack pigment in the stem, between bulbs, and in the filaments. The larger of these has a barely visible spot at the base of the distal bulb; the specimen is somewhat faded generally, but no more so than some other specimens. The smaller specimen is quite bleached and also has the least-developed barbel of any melanostigma.
The proximal bulb is spheroidal to ovoid in shape, occasionally with 1 or both ends flattened; in 1 small specimen this bulb is long and very thin, perhaps having been damaged. The distal bulb is short-ovoid to long-ovoid and larger in every dimension than the proximal; it is almost rectangular in 1 specimen and notably smaller distally in another.
Both the proximal and distal bulbs apparently attain their largest relative length at less than 80 mm SL, after which they grow little or not at all and decrease relative to SL. The proximal bulb is 0.3%–0.5% SL in 2 specimens 58 and 72 mm, 1.2%–1.6% in 3 specimens 71–76 mm, and decreases to 0.5%–0.9% in 5 specimens 120–136 mm. The distal bulb is 0.6%–0.7% SL at 58–72 mm, 1.7%–2.2% at 71–81 mm, and decreases to 1.0%–1.5% at 120–136 mm. The distal bulb is 1.2–2.5 times as long as the proximal bulb.
The distance between bulbs is 1.4% SL at 58 mm, 2.1%–2.2% in 2 specimens 72 and 85 mm, and 3.4%–4.1% in others 71–96 mm. Thereafter the distance decreases relative to SL to 2.5%–2.8% at 120–136 mm. The interspace is 1.7–3.8 times the length of the distal bulb.
Three to 7 short, simple terminal filaments arise close together either directly from the distal end of the distal bulb or from a short stem; 1 of these filaments is thicker and longer than the others, and this filament is less than 10% SL. There is no apparent change in length relative to SL with growth. The dominant filament has its axis well-pigmented about 3 melanophores wide; the remaining filaments usually have a single row of melanophores and are lighter than the strongest filament, but some may lack pigment entirely. Tiny bulblets are seen occasionally, but are absent in almost all.
The postorbital organ in the 2 largest males (135 and 136 mm) is 1.3%–1.9% SL, 39%–71% of fleshy orbit length. The next smaller male, 123 mm, has an organ which may be in the process of enlarging, 1.0% SL, 41% of fleshy orbit.
There was no color other than from blood vessels in the bulbs or other parts of the barbel of a 76 mm specimen from southwest of the Canary Islands. In a fresh 123 mm male from the same vicinity, both bulbs were light grayish blue. Parin et al. (1977) observed that both bulbs of their 85 mm specimen from Vityaz station 7285 were green (salatnyi tsvet).
LECTOTYPE DESIGNATION.—We select as lectotype ZMUC P201971, an immature male, 102.4 mm SL. D 25. A 37. P1 3. P2 7. IP 7. PV 32. VAV 18. OV 33. VAL 20. AC 18. IA 57. IC 75. OA 53. OC 71. VAV photophores over anal-fin base 7. Branchiostegal photophores 11. Premaxillary teeth 13. Mandibular teeth 16. Terminal filaments 6, 1 without pigment, the others with well-pigmented axes. Vertebrae 68, the 1st only partially ossified.
Measurements (in mm): Predorsal length 86.6, preanal length 75.1, prepelvic length 58.5, head length 13.5, barbel length 67.8, proximal-bulb length 1.0, distal-bulb length 1.5, distance between bulbs 3.0, longest filament length 3.5, snout length 6.3, fleshy orbit length 3.0, postorbital-organ length 0.7, lower-jaw length 11.5, upper-jaw length 10.5, depth behind head (greatest depth) 7.3, caudal-peduncle least depth 2.3, pectoral and pelvic fins broken, dorsal-base length 13.4, anal-base length 24.6, longest premaxillary tooth 2.0, longest mandibular tooth 1.5.
SIMILAR SPECIES.—Two other species have 2 terminal bulbs and several short, simple terminal filaments that have no well-developed bulblets or other inclusions: melanonema from the eastern Atlantic and melanostigmoides from the Pacific. In other species with 2 terminal bulbs and multiple terminal filaments, the filaments are longer than 10% SL or have prominent bulblets or inclusions, or both.
In melanonema, the distal bulb is parallel-sided and more than twice as long as wide, whereas it is ovoid and only slightly longer than wide in melanostigma. The smallest melanonema (68 mm), however, has a short, ovoid bulb and is considered to be that species only on the basis of its capture locality. It is not considered in the following discussion, but it suggests that bulb shape may not always be diagnostic. Bulb lengths and barbel length are helpful characters, but statements concerning them are tentative, because only 1 range of sizes is represented in both species: 85–102 mm in melanonema, 81–102 mm in melanostigma. The only other melanonema specimen is 148 mm; melanostigma has groups of 71–81 mm and 120–136 mm. With these limitations in mind, the barbel in melanonema is 76%–92% SL; in most melanostigma it is less than 70%, but in a 71 mm specimen it is 82% and in a 127 mm specimen, 76%. In specimens larger than 81 mm the distal bulb in melanonema is 1.7%–2.8% SL, in melanostigma 1.0%–1.6%, but in 71–81 mm melanostigma the bulb is 1.7%–2.2%. We can anticipate considerable overlap in specimens smaller than about 90 mm. When the lengths of the proximal and distal bulbs are added together for specimens larger than 72 mm, the sum in melanonema is 2.7–4.3 mm, in melanostigma 1.5–2.7 mm. The distance between bulbs is 0.6- 1.8 times the distal-bulb length in melanonema, 1.7–3.8 times in melanostigma; in most melanostigma the ratio is greater than 2.0.
In melanostigmoides the barbel is also longer than in melanostigma in most specimens at sizes greater than 85 mm (maximum 86% of SL), the proximal bulb is generally smaller (Figure 23), and the distance between the bulbs is generally smaller (at sizes over 85 mm 1.3%–2.4% of SL vs. 2.4%–4.1%, Figure 24).
DISTRIBUTION.—Atlantic Ocean north of the equator in a broad semicircle extending from near Madeira in the east southwestward to about 6°N, 35°W and northwestward to the Straits of Florida in the west. Three localities in the Indian Ocean: 1 between northern Madagascar and Africa, 2 in the central part at 4°N and 11°S. Three localities in the western Pacific Ocean: 1 just north of New Guinea and 2 near Halmahera. This is the only species of Nominostomias known to occur in both the Atlantic and the Indo-Pacific (Figure 42).
GEOGRAPHIC VARIATION.—There are few apparent differences between Atlantic and Indo-Pacific specimens of melanostigma. The distal bulb appears to be larger in Indo-Pacific specimens (Figure 23); 2 have larger bulbs than any Atlantic specimen, and 2 others equal the largest observed from the Atlantic. Similarly, the longest terminal filament is longer in Indian Ocean forms (Figure 24), where the maximum relative length is 9.3% of SL, the mean 6.2%; in the Atlantic the maximum is 5.9%, the mean 3.6%. Some of the filament difference could be due to breakage.
MATERIAL EXAMINED (5 males, 5 females, 10 unsexed).—Lectotype: ZMUC P201971 (, 102.4), 17°43′N, 64°56′W, 0–150 m (300 mw), 1920, 4 Mar 1922.
Paralectotype: BMNH 1929.7.6.105 (?, 95.5), 17°45′N, 64°56′W, 0–150 m (300 mw), 1900, 13 Mar 1922.
Non-types (Atlantic): ZMUC P202727 (?, 84.8), 13°35′N, 30°11′W, 0–~150 m (300 mw), 2200, 6 Nov 1921. USNM 206680 (, 123.4), 23°47′N, 20°59′W, 0-2100 m, 1745–2147, 19 Apr 1971. USNM 223736 (, 94.0), 07°43′N, 42°04′W, 0–100 m, 0045–0245, 23 Mar 1977. USNM 223737 (, 134.6), 18°29′N, 29°13′W, 0–155 m, 2155–0010, 26 Nov 1970. USNM 223739 (, 81.8), 05°32′N, 34°40′W, 0–100 m, 0145–0345, 20 Mar 1977. USNM 223740 (?, 72.4), 11°12′N, 53°49′W, 0–140 m, 0335–0530, 28 Mar 1977. MCZ 56656 (?, 86.5), 09°03′N, 40°41′W, 0–455 m, 2110–2310, 19 Sep 1973. ISH 1731/66 (, 135.8), 31°41′N, 17°19′W, 0–230 m, 2140–2300, 11 May 1966. ISH 323/68 (?, 75.7), 26°10′N, 19°26′W, 0–580 m, 2233–2303, 22 Jan 1968. UMML 33541 (?, 73.3), 24°25′N, 79°47′W, 0–700 m, 1515–1808, 22 Feb 1974. IOAN uncat.(?, 71.4), 19°24′N, 80°32′W, 0–1500 m, 1326–1615, 19 Mar 1973.
Non-types (Indo-Pacific): ZMUC P202848 (?, 57.5), 03°18′N, 129°02′E, 0–∼300 m (600 mw), 2145, 8 Jul 1929. ZMUC P202849 (, 126.7), 01°13′S, 138°42′E, 0–∼1450 m (2900 mw), 0730, 23 Jul 1929. ZMUC P202852 (?, 86.1), 03°14′N, 75°21′E, 0–∼150 m (300 mw), 2010, 3 Dec 1929. USNM 223738 (?, 80.5), 12°06′S, 44°21′E, 0–600 m, 19 Aug 1964. IOAN uncat. (, 120.1), 11°14′S, 88°48′E, 13 Jun 1977. IOAN uncat. (, 91.2), 04°22′N, 83°06′E, 0–1000 m, 24 Jan 1961. IOAN uncat. (, 80.6), 03°08′N, 130°57′E, 25 Mar 1975.
Eustomias melanonema Regan and Trewavas, 1930
Eustomias melanonema Regan and Trewavas, 1930:85, 86 [holotype and 1 non-type, the latter considered herein to be E. melanostigma].—Fowler, 1936:1179 [compilation; no new specimens].
Eustomias melanostigma.—Morrow and Gibbs, 1964:417, 418 [part; melanonema in synonymy; no additional specimens].—Backus et al., 1965:143 [1 specimen, examined by us].—Blache et al., 1970 [part, fig. 460].
Eustomias bibulbosus.—Parin, Sazonov, and Mikhailin, 1978:172 [2 specimens from Gulf of Guinea, 1 examined by us].
DIAGNOSIS.—Two terminal bulbs separated by a long distance (1.4%–3.5% SL, 0.6–1.8 times length of distal bulb). Barbel length 76%–92% SL. Five to 9 short (less than 6% SL) filaments, without prominent bulblets, arising together from distal bulb or from a short distal stem; 1 filament thicker and longer than the rest. Some or all filaments with pigmented axes (unpigmented or completely faded in 1 specimen). Distal bulb long (1.7%–2.8% SL), about twice as long as wide, with almost straight, parallel margins, 1.5–2.5 times proximal-bulb length. Axis of stem and between bulbs with or without pigment, a black spot at proximal end of distal bulb in those with pigment. External chevron-shaped or roundish striated areas on stem unpigmented. Middorsal paired spots between occiput and dorsal-fin origin 8.
DESCRIPTION.—A developing 68 mm specimen is considered to be melanonema on the basis of its capture locality. It could as easily be melanostigma and is omitted from the diagnosis and description. All except 1 of the remaining specimens are 86–102 mm, the largest is 148 mm. Growth changes, therefore, are noted tentatively.
Barbel length is 76%–92% SL and apparently does not change with growth. Barbel pigmentation is exceedingly variable. The axis of the stem and between the bulbs is unpigmented to moderately peppered with melanophores. A dark spot or cap at the proximal end of the distal bulb is sometimes present, sometimes absent. The filament axes are usually well pigmented, but are all unpigmented in 1 specimen. The external chevron-shaped or roundish striated areas on the stem are unpigmented.
The proximal bulb is ovoid to long-ovoid, truncate anteriorly in 1 specimen, straight-sided in another. The distal bulb is long with parallel sides (cylindrical) with the ends rounded or truncate, its length about twice its width.
The proximal bulb is 1.2%–1.5% SL at 86–102 mm, decreasing to 0.7% at 148 mm. The distal bulb decreases from 2.0%–2.8% SL to 1.7%. Apparently, neither bulb increases much or at all in size after 85 mm SL. The distal bulb is 1.5–2.0 times the length of the proximal in the smaller specimens, 2.5 times in the largest.
The distance between the bulbs also decreases relative to SL, from 2.4%–3.5% at 86–94 mm to 1.8%–2.5% at 101–102 mm and 1.4% at 148 mm. Again, there appears to be no increase in actual size with growth. The distance is 0.6–1.8 times the distal bulb length, with no apparent relationship to SL.
Five to 9 short, simple terminal filaments arise close together either from the distal end of the distal bulb or from a short stem. One filament is thicker and longer than others, and this filament is less than 6% of SL and does not change relative to SL. No bulblets were seen in the filaments.
There are no large males to indicate the definitive size of the postorbital organ. The largest, 101 mm, has an organ 1.3 mm long (1.3% SL, 46% of fleshy orbit), which is larger than in most males of other species at that size. This indicates early development and suggests the possibility of a large organ in large males.
In 2 fresh specimens, 1 (87.0 mm, sex undetermined) had a dark purple proximal bulb and a distal bulb that was dark purple basally, becoming light purple for most of its length; the other (102.0 mm female) had both bulbs light purple.
SIMILAR SPECIES.—The geographically adjacent melanostigma is the most similar species, but has an ovoid distal bulb that is only slightly longer than wide, a generally shorter barbel and distal bulb, a smaller sum of proximal- plus distal-bulb lengths, and a larger ratio of distal bulb to interspace. Details are given under melanostigma.
In Pacific melanostigmoides, the only other 2-bulbed species with multiple short filaments that lack bulblets or inclusions, the barbel is 65% SL or less (76% or more in melanonema) and both proximal and distal bulb are smaller (Figures 22 and 23).
- bibliographic citation
- Gibbs, Robert H., Jr., Clarke, Thomas A., and Gomon, Janet R. 1983. "Taxonomy and distribution of the stomioid fish genus Eustomias (Melanostomiidae), I: subgenus Nominostomias." Smithsonian Contributions to Zoology. 1-139. https://doi.org/10.5479/si.00810282.380
