César Román-Valencia

A new species of Hemibrycon (Characiformes, Characidae) from the upper San Juan River drainage, Pacific versant, Colombia.

Abstract Hemibrycon sanjuanensis, new species, is described from the upper San Juan River drainage, Pacific versant, Colombia. It is distinguished from Hemibrycon boquiae, Hemibrycon brevispini, Hemibrycon cairoense, Hemibrycon colombianus, Hemibrycon mikrostiktos, Hemibrycon metae, Hemibrycon palomae, Hemibrycon rafaelense and Hemibrycon tridens by the presence of a circular or oblong humeral spot that is located two scales posterior to the opercle (vs. 3–4 scales in Hemibrycon palomae, Hemibrycon rafaelense, Hemibrycon brevispini and Hemibrycon cairoense, and 0–1 scales, in Hemibrycon metae and Hemibrycon boquiae). It further differs from Hemibrycon colombianus in having a round or oblong humeral spot (vs. rectangular). It differs from Hemibrycon beni, Hemibrycon dariensis, Hemibrycon divisorensis, Hemibrycon helleri, Hemibrycon huambonicus, Hemibrycon inambari, Hemibrycon jabonero, Hemibrycon jelskii, Hemibrycon mikrostiktos, Hemibrycon polyodon, Hemibrycon quindos, Hemibrycon raqueliae, Hemibrycon santamartae, Hemibrycon surinamensis, Hemibrycon taeniurus, Hemibrycon tridens, and Hemibrycon yacopiae in having melanophores on the posterior margins of the scales along the sides of body (vs. lacking melanophores on margins of scales along entire length of the sides of body). The new species differs from all congeners mentioned above in having, among other features, six teeth in the outer premaxillary row arranged in a straight line (vs. five or fewer teeth not arranged in straight line except Hemibrycon cairoense with two to six teeth in the outer premaxillary row).

A new species of Tyttocharax (Characiformes: Characidae: Stevardiinae) from the Güejar river, Orinoco river Basin, Colombia

A new Tyttocharax species from the Guejar River system, near the Macarena Mountains in Colombia is described. This is the first record for the genus from the Orinoco basin. The combination of the following characters distinguish Tyttocharax metae from its congeners: presence of bony hooks on the pectoral and caudal-fin rays; bony hooks on the anal-fin rays larger than those on the pelvic-fin rays; pectoral-fin rays i,5-6,i; presence of three unbranched dorsal-fin rays; absence of an adipose fin; four scales rows between the anal-fin origin and the lateral line; and four scale rows between the pelvic-fin and the lateral line. Ecological characteristics of the habitat of the new species are also presented.

Taxonomic review of Colombian Parodon (Characiformes: Parodontidae), with descriptions of three new species

We review species of Parodon Valenciennes, 1850 from the Magdalena, Cauca, Orinoco, Amazonas, Atrato and Caribbean-Guajira River basins of Colombia using meristic and morphological characters. We recognize eight valid species, five previously described: P. apolinari Myers, from the Orinoco River basin; P. buckleyi Boulenger and P. pongoensis (Allen) from the upper Amazon; P. caliensis Boulenger, from the upper Cauca River drainage; and P. suborbitalis Valenciennes, from Lake Maracaibo basin. Three new species are described: P. alfonsoi, from the lower Magdalena River drainage; P. magdalenensis, from the middle Magdalena and upper Cauca River drainages; and P. atratoensis, from the Atrato River basin. We redescribe Parodon suborbitalis using type specimens and topotypes, and designate lectotypes. A taxonomic key is included for identification of the species, as well as geographic distribution maps.

Physicochemical and biological characterization of the Roble river, Upper Cauca, western Colombia

To determine dial and seasonal differences as well as productivity and the trophic status of the lower Roble river, a tributary of the Vieja and upper Cauca rivers of west Colombia, we sampled phytoplankton, zooplankton, fish and macroinvertebrates and recorded physicochemical variables (dissolved oxygen, percent oxygen saturation, pH, conductivity, relative humidity, environmental, water, maximum and minimum tem- peratures, width, depth, current velocity, substrate, CO 2 , COD, BOD, total calcium and magnesium hardness, total, dissolved and suspended solids, alkalinity, acidity, chlorine and turbidity) during the wet and dry seasons. Most physicochemical variables such as relative humidity, dissolved oxygen and percent oxygen saturation showed low coefficients of variation, except for oxygen deficit. The Shannon-Wiener diversity index, equity and domi- nance had low values around 0.5. We recorded eight orders, 28 families and 58 genera of macroinvertebrates, three divisions, five orders and 45 genera of phytoplankton, two divisions and six genera of zooplankton and 19 species of fishes. This river has an allochthonous-heterotrophic trophic state and productivity is oligotrophic but with a tendency to eutrophication.