Melanorivulus nigropunctatus

description

Conservation status. The species was recorded in a disturbed area, where a small dam supplies water for cattle, a common practice in wetlands in the region. Furthermore, it is inferred that some populations were probably lost due to the establishment of UHE São Domingos, a hydroelectric plant, whose dam flooded 18 km ² of the Rio Verde drainage, even though no species of Cynolebiidae were reported in its environmental impact assessment study. Presently, this species meets the criteria under the IUCN Red List (IUCN 2001) to be considered Critically Endangered (CR), with the area of occupancy less than 10 km 2 (B 2), known only at a single site (a), with projected decline (b) in occupancy area (ii) and quality of habitat (iii); it is therefore included in the category B 2 ab (ii, iii).

Two new species of Melanorivulus (Cyprinodontiformes: Cynolebiidae) from Rio Verde drainage, Upper Rio Paraná basin, Brazil

description

Description. Morphometric data is presented at Table 1. Males larger than females, largest male examined 24.1 mm SL, largest female 22.8 mm SL. Dorsal profile slightly convex from snout to end of dorsal-fin base, straight on caudal peduncle. Ventral profile weakly convex from lower jaw to origin of anal-fin, approximately straight to end of caudal peduncle. Body slender, approximately cylindrical and compressed, greatest body depth at midlength between pectoral-fin base and anal-fin base. Snout blunt. Jaws short. Short dorsal and anal fins. Dorsal-fin rays 8 – 9. Dorsal fin slightly pointed in males, rounded in females. Dorsal-fin origin on vertical through base of 8 th or 9 th anal-fin ray, and between neural spines of 21 th and 22 th vertebrae. Anal-fin rays 12 – 13. Anal fin slightly pointed in males and females. Origin of anal fin at vertical through pleural ribs of 15 th – 16 th vertebrae. Caudal fin oval shaped, longer than deep, with 31 – 32 rays. Pectoral fin rays 12 – 13. Pectoral fins rounded, with posterior margin reaching vertical at about 70 – 80 % of length between pectoralfin and pelvic-fin bases. Pelvic-fin rays 6 – 7. Pelvic-fin posterior tip reaching vertical at a

Two new species of Melanorivulus (Cyprinodontiformes: Cynolebiidae) from Rio Verde drainage, Upper Rio Paraná basin, Brazil

diagnosis

Diagnosis. The sides of body greenish blue above the anal fin base in males and the irregular black stripe between the postorbital region and the mid-length of the pectoral fin distinguishes M. nigropunctatus from all other species of the genus Melanorivulus, except from those of the M. pictus clade. The presence of black spots over the dorsal portion of the flank and head, and over the dorsum and caudal peduncle in both sexes (vs. absence of black spots or the presence of dark brown spots only on the dorsum and head), pectoral fin orange, with dark grey margin and pelvic fin orange in males (vs. pectoral and pelvic fins orange absent in other species of M. pictus clade and in all species of Melanorivulus, except in M. imperatrizensis), anal fin yellow, with a tendency to darken in the distal portion, caudal and dorsal fin yellow with narrow vertical irregular red lines (vs. never a similar color patter) distinguish M. nigropunctatus from other species of the M. pictus clade. The new species is also distinguished from the remaining species belonging to the M. pictus clade by a lower caudal fin length in males (27 – 29.7 % SL vs. 31.6 – 38.8 % SL, with exception of M. ofaie, M. plan

Two new species of Melanorivulus (Cyprinodontiformes: Cynolebiidae) from Rio Verde drainage, Upper Rio Paraná basin, Brazil

distribution

Distribution. Melanorivulus nigropunctatus is known only from its type locality, a wetland associated with a small stream which is a direct tributary of the main channel of the Rio Verde, upper Rio Paraná basin, Mato Grosso do Sul, Brazil (Fig. 4).

Two new species of Melanorivulus (Cyprinodontiformes: Cynolebiidae) from Rio Verde drainage, Upper Rio Paraná basin, Brazil