Hyphessobrycon rheophilus, a new species from rapids of the Amazon and Orinoco river basins (Characiformes: Characidae: Stethaprioninae).

A new species from rapids of Rio Aripuanã, Rio Madeira basin, in Brazil, and from the same type of habitat in the upper Rio Negro and upper Rio Orinoco basins in Brazil, Colombia, and Venezuela is described and assigned to the genus Hyphessobrycon. The new species presents an interrupted lateral line plus a single perforated scale on caudal peduncle and a small dark blotch on dorsal procurrent caudal-fin rays, features not found in the other species of Hyphessobrycon. Comments on the phylogenetic position of the new species, its rheophilic habits, and the biogeographic implications of its distribution are presented.

A new species of Creagrutus Günther (Characidae: Stevardiinae) from the Amazonian Piedmont of Colombia.

A new species of Creagrutus is described from the Amazonian Piedmont, Colombia. The new species can be distinguished from congeners by presenting the following unique combination of characters: a dark mid-lateral stripe starting at anteriormost scale of lateral line, a vertically elongated humeral blotch, absence of dark blotches on dorsal fin and at base of middle caudal-fin rays, a triangular dentigerous surface of the premaxilla, 5-6 dentary teeth, and 11-12 predorsal scales. Comparisons with congeners distributed in the piedmont region of Río Caquetá basin are presented and its relationships among species of Creagrutus is inferred from the available phylogenetic framework.

A new species of Pimelodella Eigenmann amp; Eigenmann, 1888 (Siluriformes: Heptapteridae) from the Sierra Nevada de Santa Marta, Colombia.

A new species of Pimelodella is described from northern coastal drainages of the Sierra Nevada de Santa Marta (SNSM), Colombia. The new species is diagnosed from all trans-Andean congeners by the following unique combination of characters: head length 22.2-23.

A new species of Hemigrammus (Characiformes: Characidae) from western Amazon River basin, Colombia.

A new species of Hemigrammus is described from the Amazon Basin near Leticia, Departamento Amazonas, Colombia. In common with some congeners and some Hyphessobrycon spp., the new species colour pattern lacks a humeral blotch but has a caudal-peduncle blotch.

Karyotypic Divergence of Two Co-Occurring Species of Andean Climbing Catfishes (Siluriformes: Loricarioidei: Astroblepidae).

The monotypic Astroblepidae fish family includes 81 species distributed along Central and Northern Andes in South America and Panamá in Central America; most aspects regarding its biology, taxonomy, and chromosomal features remain largely unknown. This study reports the karyotype of two sympatric Astroblepus species from the Colombian Andes, aiming to provide novel information on karyotype organization and reveal possible chromosomal rearrangements occurred on these species, through mapping of different repetitive DNA classes, including microsatellites and ribosomal DNA multigene families. The results showed differences in the chromosome number and karyotypic formula: Astroblepus grixalvii had 2n = 52 (28m+8sm +12st +4a) with the metacentric pair number 1 as the largest chromosome pair, whereas Astroblepus homodon had 2n = 54 (30m+8sm +8st +8a) and less evident chromosome size differences.

A new species of Creagrutus (Characidae: Stevardiinae) from the upper Río Magdalena, Colombia.

A new species of Creagrutus is described from several localities in the upper Río Magdalena drainage, Colombia. Creagrutus dulima n. sp.