''Symphysodon tarzoo'', the green discus, is a

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

cichlid Cichlids () are a large, diverse, and widespread family of percomorph fish in the family Cichlidae, order Cichliformes. At least 1,760 species have been scientifically described, making it one of the largest vertebrate families, with on ...

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

; specifically, to rivers of the western

Amazon Basin The Amazon basin is the part of South America drained by the Amazon River and its tributary, tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries ...

upriver from the Purus arch, although it occasionally occurs downstream. An introduced population in the

Nanay River The Nanay River is a river in northern Peru. It is a tributary of the Amazon River, merging into this river at the city of Iquitos. The lower part of the Nanay flows to the north and west of the city, while the Itaya River flows to the south a ...

is based on stock from the

Tefé Tefé, known in early accounts as Teffé, is a Municipalities of Brazil, municipality in the state of Amazonas (Brazilian state), Amazonas, northern Brazil. History As early as 1620 the Portuguese Carmelites could already boast of converts amo ...

region. The green discus is found in blackwater habitats with a high temperature of and low pH of 4.8–5.9. Although also known from

whitewater Whitewater forms in the context of rapids, in particular, when a river's Stream gradient, gradient changes enough to generate so much turbulence that air is trapped within the water. This forms an unstable current that foam, froths, making t ...

, its preference for

lentic A lake ecosystem or lacustrine ecosystem includes biotic (living) plants, animals and micro-organisms, as well as abiotic (non-living) physical and chemical interactions. Lake ecosystems are a prime example of lentic ecosystems (''lentic'' ref ...

habitats such as

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...

s means that the water contain little suspended material (unlike main sections of whitewater rivers). This species grows to a length of SL. ''S. tarzoo'' has red spots on the

anal fin Fins are moving appendages protruding from the body of fish that interact with water to generate thrust and help the fish swim. Apart from the tail or caudal fin, fish fins have no direct connection with the back bone and are supported o ...

and body, which separates it from other discus species. The scientific name was coined by Earl Lyons in 1959, and the species was revalidated by pattern,

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

and

mtDNA Mitochondrial DNA (mtDNA and mDNA) is the DNA located in the mitochondria organelles in a eukaryotic cell that converts chemical energy from food into adenosine triphosphate (ATP). Mitochondrial DNA is a small portion of the DNA contained in ...

in 2006. Later studies have confirmed its distinction, although some suggest the correct scientific name for the green discus is ''S. aequifasciatus'' (a name typically used for the blue/brown discus). No natural (wild) hybrids are known between the green discus and its relatives.

References

tarzoo Fish of the Amazon basin Cichlid fish of Brazil Endemic fish of Brazil Fish described in 1959 {{Cichlasomatinae-stub