T. pascuali is readily distinguished from all congeners by two remarkable features: possession of five pectoral-fin rays (vs. six or more) and absence of pelvic fin, girdle, and muscles (vs. presence). Some other Trichomycterus spp. lack pelvic fins, but they have six or more pectoral-fin rays.
This species has two body-coloration patterns: (1) In specimens between 20-49mm SL, ground color of body yellowish. Head covered by irregular brown spots and two regular longitudinal stripes along lateral region of body, one dorsolateral and another midlateral. Ventrolateral row of spots observed at abdominal region and caudal peduncle. Dorsal, anal and caudal fins slightly pigmented. (2) In specimens >49mm SL, head with some regular brown spots in the dorsal region, gradually lighter laterally; barbels slightly pigmented with the same coloration as head spots. Trunk yellowish with dorsal and abdominal lateral portion of the body covered by irregular spots from the lateral head region to caudal peduncle without defined pattern. Pectoral fin unpigmented, dorsal, anal, and caudal fins rays pigmented with the same coloration as the body spots.
This species was discovered in a small stream with
clear water and moderate water flow, at an elevation of 600m. The specimens were collected under rocks and aquatic vegetation in a muddy bottom area bordered by riparian vegetation.