Hyphessobrycon sebastiani, García, Carlos A., Alzate, -, Valencia, César Román - & Taphorn, Donald C., 2010

García, Carlos A., Alzate, -, Valencia, César Román - & Taphorn, Donald C., 2010, A new species of Hyphessobrycon (Teleostei: Characiformes: Characidae) from the San Juan River drainage, Pacific versant of Colombia, Zootaxa 2349, pp. 55-64: 56-61

publication ID

http://doi.org/ 10.5281/zenodo.205302

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scientific name

Hyphessobrycon sebastiani

new species

Hyphessobrycon sebastiani  , new species

Table 1, Figures 1–4View FIGURE 1View FIGURE 2View FIGURE 3View FIGURE 4

Holotype. IUQ 1942, (39.5 mm SL, male) Colombia, Pacific versant, Chocó, Istmina, San Juan River drainage, Patecucho Creek, approximately 5°09’N & 76°40’W, 7 August 2002, T. Silirio.

Paratypes. IMCN 0 429, (2, 41.3–41.8 mm SL) collected with holotype; IMCN 2193 (5, 34.2–46.0 mm SL) Colombia, San Juan River drainage, Pacific versant, Istmina, Chocó, 12 July 2003, T. Silirio; IUQ 1943 (2 C&S, 41.1–46.0 mm SL) Colombia, San Juan River drainage, Pacific versant, Istmina, Chocó, 12 July 2003, T. Silirio; MCNG 54650 (3, 34.1–46.4 mm SL) Colombia, Waguaral Creek, San Juan River drainage, Pacific versant, Istmina, Chocó, 10 August 2002, T. Silirio.

Diagnosis. Hyphessobrycon sebastiani  differs from all congeners, except H. bifasciatus  , H. balbus  , H. colombianus  , H. flammeus  , H. griemi  , H. itaparicensis  , H. savagei  , H. togoi  and H. weitzmanorum  by possessing two humeral spots and no caudal blotch. Hyphessobrycon sebastiani  is distinguished from those species by possessing: a higher number of branched pectoral –fin rays (12–13 vs. 10–11); a higher number of branched anal –fin rays (25–28 vs.17–24); a higher number of lateral scales (35–37 vs. 30–32); a higher number of scales between the lateral line and the base of the dorsal fin (eight vs. five to seven); a higher number of unbranched anal –fin rays (five vs. three to four unbranched); by the presence of three pairs of large bony hooks on anal fin of the mature males (vs. one or two pairs) and by a higher number of pored lateral –line scales (13–18 vs. 8–13, except H. balbus  with 11–22 and H. togoi  with 8–14).

Description. Morphometric and meristic data are given in Table 1. Body short and deep. Dorsal profile concave from snout to supraoccipital, then convex to dorsal-fin origin; straight from base of last dorsal-fin ray to base of caudal fin. Ventral profile of body convex from snout to base of anal fin, more pronounced behind pectorals, and from there straight to base caudal peduncle, but base of the anal fin is convex.

Head and snout long, jaws equal, mouth terminal, lips not covering externally the outer row of premaxillary teeth. Ventral part of upper jaw straight. Posterior tip of maxilla reaching the anterior margin of second infraorbital. Premaxillary teeth in two rows; outer row with four tricuspid teeth, arranged in zigzag line; inner row with six teeth diminishing gradually in size, the first four (innermost) pentacuspid and the fifth and sixth tricuspid ( Fig. 2View FIGURE 2). Maxilla long and narrow with anterior margin convex and undulated; with two tricuspid teeth; its upper tip inserts laterally to the margin of the premaxilla. Dentary elongate with the posterdorsal border partly convex, the ventral margin straight, with ten teeth on its upper-anterior border, the first four (front) teeth large and heptacuspid, followed by one smaller tricuspid tooth, and six small conic teeth that diminish in size moving away from symphysis ( Fig. 2View FIGURE 2).

Metapterygoid widened with the inferior border concave, and with small foramen in its postero-medial region. A small band of cartilage present on anterior margin uniting it with the quadrate and ventro-posteriorly to join with the hyomandibular. Ectopterygoid elongate and wide, not in contact with the quadrate. There are six narrow infraorbital bones, the first elongate, the second and fifth the longest of the series, the second with four small foramina in the middle anterior region; the third and widest of the series is not in contact with the preopercle. The ventral-anterior region of antorbital overlays the upper portion of the maxilla. Supraorbital absent. Nasal bone elongate, in contact with upper margin of premaxilla. Rhinosphenoid bony, united to orbitosphenoid by band of cartilage, with a bony projection towards ventral region of frontal. Orbitosphenoid bony, elongated anteriorly with a widened tip. Parasphenoid not divided, united to ventral surface of vomer by cartilage; posterior tip of parasphenoid in contact with basioccipital and the prootic by band of cartilage. Basihyal cartilaginous and divided. Pharyngeal plate elongate and convex, with cartilage on the dorsal and ventral margins. First gill arch with two gill rakers on hypobranchial, ten gill rakers on ceratobranchials and six gill rakers on epibranchial.

Margin of dorsal fin oblique. Proximal pterygiophores of the dorsal-fin rays inserted between neural spines 5 to 13. Dorsal fin with a small vestigial ray located anterior to base of first normal ray. Anal fin with 27 proximal radials, the first three inserted between hemal spines 11 and 12, the last modified with a small apophyses. Five elongate supraneurals, with cartilage on upper tips, inserted above the first to fourth neural spines. Pectoral girdle with a sharp dorsal process above cleithrum. Cleithrum elongate, its posterior border thickened and with rounded margin, located beneath ventral margin of opercle. Postemporal with the upper tip pointed, extrascapular elongate with the ventral margin ovoid. Postcleithrum 1 ovoid, the upper region narrow and not in contact with postcleithrum 2, postcleithrum 3 thickened and curved with a convex, bony, laminar prolongation on the antero-medial border. Three proximal radials on the pectoral girdle. Pelvic fin long, its depressed tip surpassing anal-fin origin. Pelvic bone elongate, straight and narrow, situated parallel to central axis of body. Ischial process elongate, with cartilaginous apophyses. Caudal fin bifurcate with long pointed lobes. Principal caudal rays 9/8 and with 10/9 procurrents, the first three procurrents rays of the lower caudal fin lobe modified, with elongate apophyses on upper margin. Anterior border of dorsal fin rounded, the depressed dorsal rays reach the anterior margin of adipose fin. Scales cycloid. Caudal fin without scales. Anal fin with three series of scales forming a sheath that covers the base of the first seven anal-fin rays. Total number of vertebrae 33.

Sexual dimorphism. Adult males have a pair of very large, dorsally curved, bony hooks on both sides of the fifth unbranched and first and second branched anal-fin rays ( Fig. 3View FIGURE 3).

Color in alcohol. See Figure 1View FIGURE 1. Dorsal region and head dark brown. Dense concentration of chromatophores along dorsal profile, more conspicuous from end of supraoccipital spine to dorsal procurrent rays. Posterior margin of scales above lateral margin darkened by higher concentration of small chromatophores. Anterior humeral spot rectangular, from second scale behind the opercle, above the perforated scales of the lateral line, extending to fourth scale. Frequently anterior and ventral part of this spot with a series of scattered melanophores extending horizontally, second diffuse spot separated from anterior spot by two scales. Fins translucent, with many melanophores on posterior margins. Snout, lips, and maxilla dark brown. Ventral body light yellow. Interradial membranes of paired and unpaired fins with small chromatophores, distributed along the rays. Anal fin with chromatophores more concentrated on distal end.

Distribution. Middle section of the San Juan River drainage, of the Pacific coast of Colombia ( Fig. 5View FIGURE 5). Etymology. This species is named for the younger brother of C.G-A, Sebastian.

Ecological notes. Data from three stomachs taken from specimens to be cleared and stained revealed a predominantly insectivorous diet: insect parts (69.56 % by number (N) of prey items and 34.24 % volumetric (V)), followed by Diptera  , Ceratopogonidae  (13.03 % N and 5.57 % V), Trichoptera, Hydropsichidae (8.69 % N and 10.95 % V), ant heads ( Formicidae  ) (4.34% N and 10.95% V). We also found Cyanophyceae, Spirogyra (4.34% N and 13.69% V) and unidentified digested material (20.54 %V).

Remarks. Principal component analysis (PCA) detected differences among the new species and Hyphessobrycon panamensis  , H. columbianus  , H. savagei  , H. condotensis  and H. tortuguerae  . For the first component, body depth, anal-fin length and pectoral-fin length were the most important variables. For the second component, dorsal-fin length was most important. The first component explained 90.97% of total variation, and combined with the second this rose to 94.51% ( Fig. 4View FIGURE 4).

TABLE 1. Morphometric and meristic data of Hyphessobrycon sebastiani sp. n. Standard length given in mm. Mean given in parentheses. Standard deviation = SD and Mode.

    34.1–46.4 (39.7)  
    40.1–43.8 (42.1) 51.4–55.6 (53.1)  
    26.5–31.1 (28.5)  
    44.8–51.8 (47.5) 58.8–66.3 (62.4)  
    47.6–52.4 (50.1)  
    39.2–43.1 (40.8) 39.9–45.5 (43.6)  
    30.9–32.1 (31.1)  
    22.9–27.2 (25.3) 17.4–19.2 (18.4)  
    17.9–24.4 (20.5)  
    25.8–29.4 (27.7)  
    33.4–46.4 (41.6) 30.6–50.0 (39.7)  
    32.9–40.0 (35.8)  

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Museo de Ciencias Naturales de la UNELLEZ en Guanare