Trichomycterus pauciradiatus

description

Coloration: Side of body yellow with broad dark brown stripe along lateral midline, dorsally bordered by a bright yellow zone lacking dark chromatophores; longitudinal row of dark brown small spots sometimes coalescent; below lateral stripe some dark brown dots irregularly distributed along ventral the portion of flank. Venter light yellow. Head yellow with dark brown spots on dorsal surface; dark brown blotch between eyes sometimes prolonged to posterior portion. Small spots sometimes coalescent around eye, and short dark brown bar in front of opercle. Ventral surface of head yellow with few dark brown dots. Nasal barbel brown, maxillary and rictal barbels light yellow. Pectoral fin pale yellow. Dorsal, anal and pelvic fins pale yellow. Caudal fin light yellow with central portion light brown.

Trichomycterus pauciradiatus, a new catfish species from the upper rio Paraná basin, southeastern Brazil (Siluriformes: Trichomycteridae).

description

Description: Morphometric data of holotype and paratypes are given in Table 1. Body elongated, subcylindrical on anterior portion, compressed on caudal peduncle. Dorsal profile slightly convex between snout and end of dorsal-fin base, straight to slightly convex on caudal peduncle. Ventral profile straight between lower jaw and end of anal-fin base, straight on caudal peduncle. Greatest body depth on vertical just in front of dorsal-fin origin. Skin papillae minute. Urogenital papilla conical, in vertical through anterior third of dorsal-fin. Dorsal-fin approximately triangular, origin on vertical through centrum of 20 th or 21 st vertebra. Anal fin triangular, origin on vertical through base of dorsal-fin ray 7 - 8 and through centrum of 24 th or 25 th vertebra. Pectoral-fin small, about triangular, lateral and posterior edges slightly convex. First pectoral-fin ray terminating in filament about 5 - 10 % of pectoral-fin length. Pelvic-fin about half of anal fin, covering urogenital pore, tip not reaching anal fin, in vertical through anterior portion or middle of dorsal fin; pelvic-fin bases separated; pelvic-fin origin in vertical through centrum of 18 th or 19 th vertebra. Cauda

Trichomycterus pauciradiatus, a new catfish species from the upper rio Paraná basin, southeastern Brazil (Siluriformes: Trichomycteridae).

diagnosis

Diagnosis: Distinguished from all other species of the genus in having four pelvic-fin rays (vs. five). Similar to T. reinhardti (Eigenmann) by having a unique color pattern composed of a broad dark brown stripe on the flank, dorsally bordered by a bright yellow zone without dark marks. The new species differs from T. reinhardti by possessing a more slender body (body depth 12.6 - 15.1 % SL vs. 10.5 - 12.9 % SL) and a shorter preorbital length (25.7 - 39.3 % HL vs. 41.7 - 46.2 % HL) (Tables 1 and 2).

Trichomycterus pauciradiatus, a new catfish species from the upper rio Paraná basin, southeastern Brazil (Siluriformes: Trichomycteridae).

discussion

Discussion Some authors have tentatively defined putative monophyletic assemblages within the genus Trichomycterus based on the possession of unique morphological features (e. g., Costa, 1992; Barbosa & Costa, 2003; Bockmann & Sazima, 2004). However, no phylogenetic studies encompassing all species of this genus are available, making it difficult to discuss phylogenetic relationships of most species, especially those not exhibiting features used in previous studies. Color pattern has been considered by some authors to be unreliable to diagnose species of Trichomycterus. However, color pattern has been showed to be a powerful instrument not only to diagnose species but also to establish, in agreement with other characters, possible monophyletic groups among species of the genus (Barbosa & Costa, 2003). In this regard, Trichomycterus pauciradiatus is possibly more closely related to T. reinhardti, which is endemic to the upper rio Sao Francisco basin, than to other congeners due to both species sharing a derived color pattern not found among congeners. This color pattern consists of a broad dark brown stripe along the lateral midline, bordered above by a light yellow longitudinal zon

Trichomycterus pauciradiatus, a new catfish species from the upper rio Paraná basin, southeastern Brazil (Siluriformes: Trichomycteridae).