Discus (fish)

Discus (Symphysodon spp.) are a genus of three species of cichlid freshwater fish native to the Amazon River basin. Discus are popular as aquarium fish and their aquaculture in several countries in Asia is a major industry

Taxonomy

Symphysodon discus

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.

Location and habitat

Symphysodon species inhabit the margins of floodplain lakes and rivers in the Amazon Basin of lowland Amazonia, where it is part of the highly diverse Neotropical fish fauna.
The three species of Symphysodon have different geographic distributions. S. aequifasciatus occurs in the Rio Solimões, Rio Amazonas and the Río Putumayo-Içá in Brazil, Colombia and Peru. In contrast the distribution of S. discus appears to be limited to the lower reaches of the Abacaxis, Rio Negro and Trombetas rivers. S. tarzoo occurs upstream of Manaus in the western Amazon.^{[citation needed]}

Appearance

Red turquoise discus

Captive breed

Like cichlids from the genus Pterophyllum, all Symphysodon species have a laterally compressed body shape. In contrast to Pterophyllum, however, extended finnage is absent giving Symphysodon a more rounded shape. It is this body shape from which their common name, "discus", is derived. The sides of the fish are frequently patterned in shades of green, red, brown, and blue. The height and length of the grown fish are both about 20–25 cm (8–10 in).^{[citation needed]}

Reproduction and sexual dimorphism

Discus with two of its young nearby

Another characteristic of Symphysodon species is their care for the larvae. As for most cichlids, brood care is highly developed with both the parents caring for the young. Additionally, adult discus produce a secretion through their skin, which the larvae live off during their first few days. This behaviour has also been observed for Uaru species. However when bred in captivity the larvae will tend to live off their parents secretion for up to 2 weeks.