Discus (fish) - Taxonomy

Taxonomy

Discus are fish from the genus Symphysodon, which currently includes three species: the common discus (Symphysodon aequifasciatus), the Heckel discus (Symphysodon discus), and Symphysodon tarzoo. However, a further investigation published in August 2007 suggested that the genus held these three species: S. aequifasciatus (the green discus), S. haraldi (the blue/brown/common discus), and S. discus (the Heckel discus).

Other (sub)species have been proposed, but morphometric data (unlike in Pterophyllum, the freshwater angelfish) varies as much between individuals from one location as across the whole range of all discus fish species. S. tarzoo was described in 1959 and applies to the red-spotted western population. S. aequifasciatus and S. discus, meanwhile, seem to hybridise frequently in the wild or have diverged recently, as they lack mitochondrial DNA lineage sorting but differ in color pattern and have dissimilar chromosomal translocation patterns. S. discus occurs mainly in the Rio Negro. Whether S. haraldi is indeed distinct from S. aequifasciatus remains to be determined; if valid it is widespread but it might just be a color morph.