Chalceus Genus  

The characid Chalceus genus includes species that are relatively common in rivers in the Amazon, the Orinoco watershed and the flooded areas of Guyana.

These fish reach up to 30 cm in length and are easily recognized for having a shiny silver body, red fins and large scales, attributes for which they are used in aquariums.

Géry recognized as valid only two species of Chalceus: Chalceus macrolepidotus and Chalceus erythrurus.

These two nominal forms were distinguished based on the color pattern, and mainly in the presence of a humeral stain on Chalceus erythrurus, which is absent on Chalceus macrolepidotus, together with differences in the color of the fins of the fish in life.

The Chalceus genus is diagnosed phylogenetically based on the following synapomorphies:

a) Presence of supramaxilla;
b) Three series of teeth on premaxilla;
c) Internal series of dentary teeth formed by a large symphyseal conical tooth followed by a gap and a series of smaller conical teeth;
d) Reduced anterolateral process of mesethmoid;
e) Scales situated dorsal to lateral line much larger than those ventral to it;
f) Relative size of scales along lateral line other than on caudal peduncle alternatively large and small. In addition, the combination of the following characters is useful to distinguish the species of Chalceus among characiforms: bright silvery body, red fins and short anal fin.

After a taxonomic review, the neotropical characid fish of the genus Chalceus Cuvier, 1817, had a total of 5 recognized species (including three new species): Chalceus epakros, Chalceus guaporensis, Chalceus spilogyros, Chalceus macrolepidotus and Chalceus erythrurus.

Below are links to more known species:

Chalceus erythrurus

Chalceus macrolepidotus

Identification Key for the species of the Chalceus genus:

1 - Absence of distinct spots or conspicuous stripes of dark pigmentation on body (except for wide and inconspicuous longitudinal band formed by chromatophores located superficially in the skin in some specimens during reproductive period)  ...........................................Chalceus macrolepidotus
1 " - Presence of dark pigmentation forming humeral spots or stripes ................................................................................2
2 - Humeral spot absent or poorly defined, round to vertically elongate and located deep under scales; presence of narrow longitudinal dark stripe from posterodorsal margin of opercle to caudal peduncle; snout relatively acute; median fontanel between frontals and parietals absent .................................................................................4
2 " - Presence of conspicuous humeral spot, round in shape and located superficially beneath scales; lateral surface of body usually with reticulate pattern; snout rounded; median fontanel present between frontals and parietals ....................................................................3
3 -  Humeral spot with notch on its posterodorsal margin; reticulate pattern of body coloration more evident along series of scales posterior to humeral blotch; pelvic and anal fins dark; caudal-fin lobes robust and rounded .................................................Chalceus erythrurus
3 " - Humeral spot without notch on its posterodorsal margin; reticulate pattern of body coloration uniformly distributed over lateral and dorsal portions of body; pelvic and anal fins hyaline; caudal-fin lobes elongate and slender  .................................Chalceus spilogyros
4 - Number of branched pelvic-fin rays 7 .................Chalceus guaporensis
4 " - Number of branched pelvic-fin rays 8 ..............Chalceus epakros

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