Trichomycterus tropeiro

description

Description. Morphometric data for holotype and paratypes given in Table 1. Body elongate, roughly cylindrical close to head and gradually more compressed in trunk towards caudal-fin. Dorsal e ventral profiles of head straight. Profiles of trunk straight dorsally and slightly convex ventrally. Dorsal and ventral profiles of caudal peduncle straight. Integument thick, especially over base of dorsal-fin and anal-fin. Small papillae covering entire surface of skin, most prominent on lips and ventral, dorsal, and lateral surfaces of head. Holotype Range Mean SD Head wide and depressed, longer than wide, the transversal section at posterior tip of opercle wider than anteriorly at nostril, snout slightly rounded. Lateral region of eye slightly swollen by jaw muscles in both large and small specimens. Eyes rounded, well defined rim, dorsally oriented, covered by thin and transparent skin, not distinctly separated from surface of eyeball. Ocular structures readily visible on surface of skin, not deeply sunken. Orbital rim not free. Anterior nostril larger than posterior nostril, surrounded by fleshy flap of integument, posterolaterally continuous with nasal barbel. Posterior nostril surrou

A new Trichomycterus lacking pelvic fins and pelvic girdle with a very restricted range in Southern Brazil (Siluriformes: Trichomycteridae)

diagnosis

Diagnosis. Trichomycterus tropeiro is distinguishable from other species of the genus by the absence of the pelvic girdle, except T. candidus and T. catamarcensis. Trichomycterus tropeiro differs from T. candidus by head length (20.4 – 23.1 vs. 14.7 – 16.1 % SL); pectoral-fin length (12.8 – 14.7 vs. 8.6 – 9.3 % SL); interorbital distance (19.6 – 25.3 vs. 26.6 – 32.3 % HL); number of dorsal procurrent caudal-fin rays (13 – 14 vs. 16 – 19); ventral procurrent caudal-fin rays (9 – 10 vs. 16 – 18); pectoral-fin unbranched rays (6 vs. 5); and branchiostegal rays (9 vs. 8). Trichomycterus tropeiro differs from T. catamarcensis by body depth (13.9 – 18.1 vs. 8.9 – 12.7 % SL); caudal peduncle depth (10.9 – 13.5 vs. 7.1 – 8.5 % SL); head length (20.4 – 23.1 vs. 15.6 – 19.4 % SL); interorbital distance (19.6 – 25.3 vs. 26.3 – 34.7 % HL); number of dorsal-fin unbranched rays (7 vs. 8 – 9); pectoral-fin unbranched rays (6 vs. 7); analfin unbranched rays (5 vs. 7 – 9); ventral procurrent caudal-fin rays (9 – 10 vs. 11 – 12); branchiostegal rays (9 vs. 5 – 6); and pleural ribs (13 – 14 vs. 18 – 20).

A new Trichomycterus lacking pelvic fins and pelvic girdle with a very restricted range in Southern Brazil (Siluriformes: Trichomycteridae)

distribution

Distribution. Known from the localities of the type series, three points located in the rio das Antas, two of them very close, and in one tributary stream (Fig. 3). The rio das Antas is part of laguna dos Patos system, having a length of 390 km to its confluence with the rio Guaporé, where both form the rio Taquari, crossing over 140 km before emptying into the rio Jacuí. Ecological notes. Trichomycterus tropeiro occurs in environments with clear water, fast current, bottom composed of gravel, pebbles and stones, above 1000 m. The stomach of the two specimens cleared and stained contained nymphs of Ephemeroptera and larvae of Diptera (Chironomidae) and Trichoptera. The following species of fish occur syntopically with T. tropeiro: Astyanax brachypterygium Bertaco & Malabarba, 2001; Astyanax sp., Cnesterodon brevirostratus Rosa & Costa, 1993; Eurycheilichthys sp., Jenynsia eirmostigma Ghedotti & Weitzman, 1995 and Pareiorhaphis hystrix (Pereira & Reis, 2002). Trichomycterus tropeiro seems to be relatively rare, with low populational densities. Almost all specimens were collected near the same locality, during an one year ecological study with monthly collecting samples. Even with th

A new Trichomycterus lacking pelvic fins and pelvic girdle with a very restricted range in Southern Brazil (Siluriformes: Trichomycteridae)

etymology

Etymology. The name is an allusion to the old drovers paths that connected the States of Rio Grande do Sul and São Paulo and crossed the Municipalities of São José dos Ausentes and Cambará do Sul. A name in apposition.

A new Trichomycterus lacking pelvic fins and pelvic girdle with a very restricted range in Southern Brazil (Siluriformes: Trichomycteridae)