Hyphessobrycon sebastiani

description

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. 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) t

A new species of Hyphessobrycon (Teleostei: Characiformes: Characidae) from the San Juan River drainage, Pacific versant of Colombia

diagnosis

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).

A new species of Hyphessobrycon (Teleostei: Characiformes: Characidae) from the San Juan River drainage, Pacific versant of Colombia

discussion

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. 4).

A new species of Hyphessobrycon (Teleostei: Characiformes: Characidae) from the San Juan River drainage, Pacific versant of Colombia

distribution

Distribution. Middle section of the San Juan River drainage, of the Pacific coast of Colombia (Fig. 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).

A new species of Hyphessobrycon (Teleostei: Characiformes: Characidae) from the San Juan River drainage, Pacific versant of Colombia