Hemibrycon taeniurus ( Gill, 1858 )

Bertaco, Vinicius A. & Malabarba, Luiz R., 2010, A review of the Cis-Andean species of Hemibrycon Günther (Teleostei: Characiformes: Characidae: Stevardiinae), with description of two new species, Neotropical Ichthyology 8 (4), pp. 737-770 : 762-765

Hemibrycon taeniurus ( Gill, 1858)

Figs. 23-24

Poecilurichthys taeniurus Gill, 1858: 418 (original description; type locality: Island of Trinidad).

Tetragonopterus taeniurus . - Günther, 1864: 317 ( Trinidad).

Tetragonopterus (Hemibrycon) trinitatis Lütken, 1875: 234 (original description; type locality: Trinidad Island, West Indies). -Eigenmann, 1927: 412 (synonym of H. taeniurus Gill , Trinidad). - Lima et al., 2003: 159 (species inquirenda in Characidae ).

Tetragonopterus guppyi Regan, 1906:384 (original description; 5 type specimens 65-85 mm TL; type locality: Glenside Estate stream, at the foot of the n. range of hills, Trinidad I.). [NEW SYNONYM]

Hemibrycon taeniurus . -Eigenmann, 1909: 327 (listed).

Hemibrycon guppyi . -Eigenmann, 1909: 327 (listed; distribution: Trinidad).

Hemibrycon guppii [error]. -Eigenmann, 1910: 432 (listed; distribution: Trinidad).

Diagnosis. Hemibrycon taeniurus is distinguished from most of its congeners by the number of branched anal-fin rays (25- 29 vs. 15-24, Fig. 2 ). From the species sharing similar lateral line counts, it differs from H. boquiae by the number of scale rows above lateral line (8 vs. 6-7), and by the total number of vertebrae (39-41 vs. 41-43); from H. brevispini by the number of cusps of three anteriormost dentary teeth (5 vs. 3), and by absence of bony hooks in the caudal-fin rays of males (vs. presence); from H. cairoense , H. huambonicus and H. polyodon by the number of lateral line scales (40-42 vs. 43-46, 44-48 and 42-45, respectively); from H. dariensis by the number of cusps of second tooth of premaxillary inner row teeth (5 vs. 7), and by the absence of pigment in the distal tip of rays just above and below to middle caudal-fin rays; from H. divisorensis and H. surinamensis by the absence of a wide black asymmetrical spot covering base of caudal-fin rays; from H. inambari by the number of scales along anal-fin base scale sheath (10-15 vs. 6-10); from H. jabonero by the number of caudal peduncle scales (16 vs. 14); from H. jelskii by the size of humeral spot (over 4-5 vs. 7-9 horizontal series of scales); from H. metae by the number of cusps of second tooth of premaxillary inner row teeth (5 vs. 7); from H. quindos by the number of scale rows above lateral line (8 vs. 5-7); and from H. raqueliae by the number of predorsal scales (15-19 vs. 10-13) and by the number of cusps of first maxillary tooth (3 vs. 5).

V. A. Bertaco & L. R. Malabarba 763

Description. Morphometric data for H. taeniurus summarized in Table 7. Largest male 65.1 mm SL, largest female 81.8 mm SL. Body compressed and moderately elongate; greatest body depth anterior to dorsal-fin origin. Dorsal profile of head slightly convex. Dorsal body profile convex from occipital bone to base of last dorsal-fin ray; straight from this point to adipose-fin origin. Ventral profile of head slightly convex. Ventral body profile convex from pectoral-fin origin to pelvicfin origin, and straight to slightly convex to anal-fin origin. Body profile along anal-fin base posterodorsally slanted. Caudal peduncle elongate, nearly straight to slightly concave along dorsal and ventral margins.

Snout rounded from margin of upper lip to vertical through anterior nostrils. Head small. Mouth terminal, mouth slit nearly at horizontal through middle of eye. Maxilla long and slightly curved, aligned at angle of approximately 45º to longitudinal body axis, and its posterior tip extending below orbit, reaching nearly to vertical through center of eye.

Premaxilla with two tooth rows; outer row with 4-6, tricuspid teeth with central cusp slightly longer; inner row with 4 tetrato pentacuspids teeth, gradually decreasing in length from first to third teeth and last smaller; central cusp twice or three times longer and broader than other cusps. Maxilla toothed with 7-15 uni- to tricuspid teeth, with central cusp longer. Three anteriormost dentary teeth larger, with 5 cusps, followed by medium sized tooth with 3-5 cusps, and 10-13 teeth with 1- 3 cusps or conical; central cusp in all teeth two to three times longer and broader than other cusps. Cusp tips slightly curved posteriorly and lingually ( Fig. 24 ).

Dorsal-fin rays ii,8 (n = 39); first unbranched ray approximately one-half length of second ray. Dorsal-fin origin located posterior to middle of SL and posterior to vertical through pelvic-fin origin. Profile of distal margin of dorsal fin nearly straight to slightly concave. Males with bony hooks in distal one-third of first branched rays.Adipose-fin located at vertical through insertion of last anal-fin rays.Anal-fin rays ii-vi,26-29 (two with 25, mode = 27, n = 39, Fig. 2 ). Anal-fin profile slightly concave in males and females.Anal-fin origin approximately at vertical through insertion in the last dorsal fin rays. Anal-fin rays of males bearing one pair of developed bony hooks along posterolateral border of each segment of lepidotrichia, along last unbranched ray and twelfth to fifth branched rays, and small bony hooks on remaining rays. Hooks usually located along posteriormost branch and distal 1 / 2 to 2 / 3 of each ray. Pectoral-fin rays i,10-12 (mode = 11, n = 39). Pectoral-fin tip surpassing pelvic-fin origin in males and nearly reaching in females. Males with bony hooks on distal portion of unbranched and all branched rays. Pelvic-fin rays i,6,i (rarely i,7, n = 39). Pelvic-fin origin located 4-5 predorsal scales anterior to vertical through dorsal-fin origin. Pelvic fin of males usually bearing 1 small bony hook per segment of lepidotrichia along ventromedial border of all branched rays. Caudal fin forked with 19 principal rays without bony hooks (n = 39); lobes similar in size. Caudalfin base have a few scales. Dorsal procurrent rays 11-13, and ventral procurrent rays 10-12 (n = 7).

764 A review of the Cis-Andean species of Hemibrycon

Scales cycloid, moderately large. Lateral line complete with 40-42 (mode = 40, n = 39, Fig. 3). Scale rows between dorsalfin origin and lateral line 8 (n = 39); scale rows between lateral line and pelvic-fin origin 5-6 (mode = 6, n = 39). Predorsal scales 13-16, arranged in regular series (mode = 14, n = 36). Scales rows around caudal peduncle 16 (n = 38). Axillary scale on pelvic-fin origin extends posteriorly covering 2-3 scales. Scale sheath along anal-fin base with 10-15 scales in single series, extending to base of most anterior branched rays.

Precaudal vertebrae 17-18; caudal vertebrae 22-24; total vertebrae 39-41 (n = 7). Supraneurals 5-7 (n = 7). Gill rakers on upper limb of outer gill arch 7-8, and on lower limb 11-13 (n = 25).

Color in alcohol. Holotype discolored. Color description based on non-type specimens. General ground body color yellowish. Dorsal portion of head and body with concentration of black chromatophores. Dorsolateral portion of head and body with scattered black chromatophores. One large and vertical black humeral spot, located over third to fifth lateral line scales and extending over 4-5 horizontal series of scales, including lateral line. Midlateral dark stripe extending from humeral region to middle caudal-fin rays, broad in the caudal peduncle. Abdominal region almost devoid of black chromatophores. Dorsal and caudal fin with black pigmentation diffuse and anal fin with small black chromatophores along its border forming narrow stripe. Pectoral, pelvic and adipose fins hyaline ( Fig. 23 ).

Sexual dimorphism. Males of Hemibrycon taeniurus are easily recognized by the presence of bony hooks on the dorsal-, pectoral-, anal- and pelvic-fin rays. Males and females slightly differ in pectoral- and pelvic-fin lengths and body depth ( Table 7). Mature males with gill gland on first gill arch, covering the first branchial filaments.

Distribution. Hemibrycon taeniurus is known inhabiting river basins from West Trinidad Island, Trinidad and Tobago ( Fig. 4 ).

Remarks. Theodore Gill described Poecilurichthys taeniurus in 1858 when he traveled to the West Indian Islands. In his original description Gill (1858: 418-419) did not provide a catalog number nor museum name for the type material, but the author remarked that “specimens of most of the species which are being described have been deposited in the museum of the Smithsonian Institution, and in the private cabinets of Messrs. Stewart & Brevoort”. Vari & Howe (1991) report no type specimens of P. taeniurus in the Smithsonian catalog of type specimens of Characiformes .

Later in 1875, Christian Lütken redescribed Tetragonopterus taeniurus (Gill) and described Tetragonopterus (Hemibrycon) trinitatis from Trinidad. Lütken did not explain to which museum belong the specimens used in his descriptions. According to Lütken (1875: 234) a glass of “tetragonopters” from Trinidad, that Mr. Riise obtained from Dr. (?Hr.) Gill at his return from that island, classified as Brevortia [sic] taeniata Gill, contained two specimens of T. taeniurus (Gill) , and seven specimens of a form that looks closely related to Tetragonopterus . These seven specimens were found to lack the dark humeral spot, and to have a maxilla equipped with small teeth in a greater part of its length, being referred by Lütken to the subgenus Hemibrycon , as T. (H.) trinitatis .

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Regan (1906: 383-384) redescribed T. taeniurus based on two specimens from Trinidad, reporting that received one specimen from the Copenhagen Museum as T. trinitatis , commenting: “Gill’s description of T. taeniurus is, so far it goes, perfectly applicable to T. trinitatis , and there can be but little doubt of their identify”. In the same work, Regan proposed a new species, H. guppyi , from Trinidad Island, and presented the only possible differences between these species: “ H. taeniurus has diameter of eye 2.5 in the HL and a little greater than interorbital width, and H. guppyi has diameter of eye 3-3.5 in the HL and less than interorbital width”.

In the catalog of fish types of Zoological Museum of Copenhagen, Nielsen (1974) reported the five syntypes of Tetragonopterus trinitatis (ZMUC 962, 963, 966-968), referring the species as a synonym of Hemibrycon taeniurus (Gill) . Lütken worked at ZMUC from 1852 to 1899 (Alves & Pompeu, 2001) and probably the specimens were carried by him for that institution or donated by Gill.

Boeseman (1960) in “The fresh-water fishes of the island of Trinidad ” provided a table with some distinct characters for H. taeniurus and H. guppyi . Boeseman (1960) and Géry (1962, 1977) distinguished these species by head length, orbital diameter and interorbital width, and commented that (Boeseman, 1960: 93) “These differences, though apparently sufficient for specific discrimination, left some room for doubt, especially since the variability in the discriminative characters still remained to be determined”, but decided to maintain H. guppyi as a separate species from H. taeniurus , although knowing that analysis was limited by the small number of specimens and mostly by not comparable sizes of the specimens available of each nominal species.

The syntypes of H. taeniurus are somewhat damaged with some caudal-fin rays broken and lacking several body scales. The dentition is preserved. The syntypes of H. guppyi are in good condition for all body measurements. We have analyzed the type series of H. taeniurus and T. Carvalho and R. Reis analyzed the types of H. guppyi when visiting the BMNH. We have compared the data of these species and did not find significant differences to distinguish the two species. Only the snout length in H. guppyi is slightly larger than the syntypes of H. taeniurus . This difference can be related to the observed differences in the standard length range between the type series of the two species ( Table 7). New specimens from Trinidad were analyzed and no significant differences were found when compared with the type series of both species. Since there are no diagnostic features to support the recognition of two species, H. guppyi is herein considered a junior synonym of H. taeniurus .

Material examined. Syntypes. Hemibrycon taeniurus, ZMUC 962- 963, 2, 42.0- 50.6 mm SL, ZMUC 966-968, 3, 33.0-45.0 mm SL, Island of Trinidad, Trinidad. Hemibrycon guppyi, BMNH 1906.6.23.13-17, 5, 46.3-73.4 mm SL, Trinidad. Non-type specimens. Trinidad and Tobago, Trinidad Island: AMNH 215239, 11 of 22 (2 c&s), 57.4- 81.8 mm SL, AMNH 215301, 5 of 10, 57.1-71.2 mm SL. CAS 70076, 3, 44.1-87.3 mm SL, West Indies, Guppy. INHS 40083, 2, 36.9-40.5 mm SL, río Quare, río Cunapo drainage, 1 km E Valencia on road to

Arima, St.Andrew County, ca. 10º39’N 61º13’W, 31 Jan 1997 . MCNG 8199 , 3 of 5 (1 c&s), 53.4-66.1 mm SL, río Guanapo , 21 Jun 1983 . ROM 61651, 1 , 65.8 mm SL, from a few streams of freshwater, 10º25’00”N 61º08’00”W . USNM 290408 , 2 (x-ray), 49.4-53.8 mm SL, río Maracas, Jul-Aug 1987 . USNM 290413 , 2 (x-ray), 58.1-65.0 mm SL, río Matura , 23 Jul 1987 .

Figures

Fig. 23. Hemibrycon taeniurus,AMNH 215239, male, 68.5 mm SL, Island of Trinidad, Trinidad and Tobago.

Fig.24.Hemibrycontaeniurus,MCNG8199,female,57.5 mmSL. Scanning electron micrograph of right side upper and lower jaws. Scale bar = 1 mm.

Fig. 2. Tukey box plots of number of branched anal-fin rays in Hemibrycon species. Mean represented by thick vertical bar, and 25th and 75th percetiles as lateral borders of box plots. Number in parentheses = N.

Fig. 4. Map of central and northern South America showing geographic distribution of Hemibrycon beni (1, solid hexagon), H. divisorensis (2, open triangle), H. helleri (3, ellipse), H. huambonicus (4, solid triangles), H. jelskii (5, solid dots), H. inambari (6, rectangles), H. metae (7, solid squares), H. mikrostiktos (8, open square), H. polyodon (9, inverted triangle), H. surinamensis (10, solid diamonds), H. taeniurus (11,Trinidad Island), H.tridens (12, open circle).Some symbols represent more than one lot or locality of specimens. 1-12 = type locality of each species.