Discus Symphysodon discus

The Discus is a species of tropical Cichlid, found in the Amazon basin of South America. There are three recognised sub-species of the Discus which are the Green Discus, the Blue Discus and the Brown Discus. The Discus was first described by Dr. Heckel in 1840 and despite variations in colour, all are similar in appearance but are found in different geographic locations. There is however some disagreement over the scientific names for each species, but many agree that most captive bred Discus are thought to have originated from these three sub-species.

Nicknamed the “pompadour fish,” for their distinctive look, discus have a round, flat body similar in shape to a disk. They vary in color, donning hues of green, red, brown and blue and have dark vertical stripes. These stripes serve a dual purpose: to aid communication within a school of discus and to camouflage the fish from predators.

**Habitats and species:**

Found in slow-moving freshwater, discus live in tributaries in the Amazon River Basin. Schools of discus hide in underwater debris away from predators. Their population is believed to be stable. Fish, turtles, birds and bats are among those that prey on discus. Symphysodon, colloquially known as discus, is a genus of cichlids native to the Amazon river basin. Due to their distinctive shape and bright colors, discus are popular as freshwater aquarium fish, and their aquaculture in several countries in Asia is a major industry. They are sometimes referred to as pompadour fish.

Larger species of Fish, Turtles and other water-dwelling animals are the most common predators of the Discus, along with other predators such as Bats and Birds that hunt the Discus from the sky above. Discus populations across South America are also threatened by habitat destruction, caused both by deforestation and pollution of the surrounding water.

There are currently three recognized species in this genus: Symphysodon aequifasciatus Pellegrin, 1904 (Blue discus) Symphysodon discus Heckel, 1840 (Red discus or Heckel discus) Symphysodon tarzoo E. Lyons, 1959 Discus are fish from the genus Symphysodon, which currently includes the above species. However, another review of the genus 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). Further arguments have been made that S. tarzoo was not described in accordance with ICZN rules and thus should be considered invalid and replaced with S. haraldi, currently considered a synonym of S. aequifasciatus by FishBase. 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. 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. 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). There is no real sexual dimorphism for this fish. In breeding form varieties, solid red discus (red melon, red cover) females are generally redder than males. 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.

**Physiological features:**

The Discus is a medium sized Fish, with a round, flattened body and large extended fins which also add to it's disk-like shape (from which it get it's name). Discus have small mouths and small bright red eyes, and vary in colour depending on the species (either green, blue or brown in the wild, but there are many new variations found in aquariums around the world today such as red). The round body of the Discus also has nine dark, vertical stripes which are thought to be used both for camouflage (along with it's colour and flattened body) and to communicate within the school. The Discus is one of only a few Cichlid species found outside of Africa. They are found inhabiting sections of deep, calm, well-wooded waters in the Amazon Basin and it's tributaries. These slow-moving rivers and backwaters of the Amazon river system that stretch through Brazil, Columbia and Peru, provide the perfect habitat for these large Fish, which generally shelter amongst the submerged roots and branches. Discus are known to be fussy about the water conditions in artificial habitats and are not for the inexperienced keeper.

**Socialising and spawning:**

In their natural environment, Discus inhabit soft, acidic, and very warm waters, where there is less competition from other Fish. Unlike many other Cichlid species, the Discus is a very sociable Fish and is often found in large groups (known as schools), in their native habitats. Living in these large groups means that the Discus displays very advanced behaviour for a Cichlid, as other species are not schooling Fish. Discus are generally mild mannered but are known to become aggressive within their pair bonds, or when defending their young or territory. One common observation from those kept in tanks, is that the Fish at the bottom of the social ladder, can be bullied extensively by groups of Discus higher up the chain, so much in fact that it can lead to death in some cases. Discus form pair bonds when they are about 75% of their adult size and these pairs tend to remain together for life. They choose a nearly vertical spawning site, which is then cleaned in preparation for the female to lay between 80 and 400 eggs. The male then fertilises them and both parents help to guard their eggs until they hatch. Like other Cichlids, Discus parents care for their young well and even secrete a slimy substance through their scales for their fry to feed off for the first couple of weeks. Discus can live until they are between 10 and 15 years old but it is not uncommon for those kept in well-run artificial habitats, to reach even older ages.

To reproduce, male and female discus together choose and clean a spot where the female will lay between 80 and 400 eggs. The male fertilizes the eggs, and both parents guard the eggs until they hatch. After hatching, the fry eat the slime off their parents’ skin until they’re old enough to eat larger pieces of food. Juvenile discus can live in groups but as they age will start to form bonded pairs and become territorial against other couples. A discus’ diet includes worms, small crustaceans, insects, insect larvae and plant matter. This fish grows approximately 6 to 8 inches in height and length.

**Diet:**

Like many other Fish, Discus will eat almost anything that will fit in their mouths. Despite this, they have a predominately meat-based diet that is high in protein. They mainly feed on small Fish and fry, along with Larvae and other Aquatic Insects, and invertebrates such as Worms. They tend to eat relatively slowly, grazing through the surrounding waters for tasty morsels. Those kept in captivity are also commonly fed Brine Shrimp and Bloodworm which are both protein-rich, along with standard Fish flakes (although this needs to be monitored to avoid over feeding). Discus inhabit areas where there is plenty of underwater debris for them to hide amongst. Their unique shape, colours and markings also provide them with camouflage from approaching predators in the Amazon river system.

**Aquariums:**

The Discus today is an incredibly popular aquarium species and it is thought to be one of the most written about tropical Fish, over a period of just 50 years. Although Fish today are all thought to have come from the green, brown and blue Discus in the wild, others colours are much more common in tanks including yellow, black and red. Today there is a major industry behind the captive breeding of Discus, which primarily occurs in Fish farms in a number of countries in Asia. They are relatively peaceful Fish, co-inhabiting their surroundings with other, generally smaller Fish that provide no competition for food. The grace and elegance of the Discus have fascinated Fish enthusiasts from around the world since they were first discovered in South America in the mid 1800s. However, excessive captive breeding has led to the fading of their dark stripes meaning that they can communciate less effectively within the group. They can also be very difficult to keep in artificial habitats as a great deal of care and attention needs to be paid to both their water quality and their feeding, along with the other species that they are sharing their environment with. Today, the Discus is listed as a Threatened species in it's natural habitat meaning that if the situation progresses unchanged, the Discus will be at threat from extinction in the wild in the near future. Although many variations of Discus occur in tanks around the world, population numbers of the original Discus species in the wild are declining, primarily due to the decreasing quality of the surrounding water.