Golden Tetra (Hemigrammus rodwayi)
Family: Characidae, Hemigrammus Clade
Common Name: Golden Tetra
Origin and Habitat: The Guyanas, Suriname, and the Amazon basin in Peru and Brazil. Occurs in slow streams and floodplain lakes; in coastal rivers it sometimes inhabits mildly brackish water. Only wild-caught fish have the golden colouration.
Compatibility/Temperament: Peaceful, suitable as a community fish with similar characins, rasbora, danio, anabantids, dwarf cichlids, small catfish and loaches. Must be kept in a group of at least six, preferably more.
Golden Tetra Diet
Accepts most prepared foods including flake and frozen. Feedings of live and frozen foods will help to maintain the golden colouration on wild-caught fish.
Grows to 2.25 inches.
Minimum Tank Suggestion
24 inches in length.
Water parameters for Golden Tetra
Soft (hardness to 12 dGH) acidic (pH below 7.0) water, temperature 24-28C/75-82F.
An interesting fish because of its golden colouring, giving the impression of having been dusted with gold powder. This is actually guanin secreted by the fish as a protection against a parasite that occurs in its habitat waters, and only wild-caught fish have this colouration. Tank-raised fish do not develop the golden colouring but are a grey-silver. The accompanying photos illustrate the wild golden fish (first photo) and the grey-silver colouration of tank raised fish (second photo).
Females are rounder, and males have a white border on the front of the anal fin which is otherwise more reddish than the female's fin.
This species is sometimes seen under the name Hemigrammus armstrongi. This description was given by Schultz and Axelrod in 1955 to the first fish of this species discovered with the golden colouration, thinking it was a new species. Lima & Oyakawa in Reis et al. (2003) established the name as a synonym of the valid H. rodwayi.
The genus Hemigrammus--the name derived from the Greek and meaning "with half line," a reference to the incomplete lateral line--was erected as a subgenus of Poecilurichthys by T.N. Gill in 1858 but has been recognized as a distinct genus since Gery (1977). There are presently about 50 valid species. The classification is deemed incertae sedis [Latin, "of uncertain placement"]. It was formerly considered within the Subfamily Tetragonopterinae, but Javonillo et.al. (2010) suggest that this subfamily should be restricted to species within the genus Tetragonopterus since they do not share physiological characteristics with species in other genera such as Hemigrammus.
None of the diagnostic characteristics presently used to describe species in Hemigrammus, including the incomplete lateral line which gave rise to the genus name, are unique to the genus. Mirande (2009) states that the genus is not monophyletic, a view shared by most ichthyologists working with the characidae. [A monophyletic genus is one wherein the species share a common ancestor, thus linking them together physiologically.] Mirande has proposed several revisions to the family Characidae based upon phylogenetic diagnosis. Some genera have been moved to a new subfamily, while others are now (temporarily) assigned to a specific clade within the family pending further study.
Hemigrammus has until recently been differentiated from Hyphessobrycon solely on the basis of the fish in Hemigrammus possessing a scaled caudal fin; this however is now known to be unreliable, since it occurs in intermediate conditions (de Lucina, 2003).
de Lucena, Carlos Alberto Santos (2003), "A new characid fish, Hyphessobrycon scutulatus, from the Rio Teles Pires drainage, upper Rio Tapajos system (Ostariophysi: Characiformes: Characidae)," Neotropical Ichthyology 1 (2), pp. 93-96.
Gery, Jacques (1977), Characoids of the World, TFH Books.
Javonillo, Robert, Luiz R. Malabarba, Stanley H. Weitzman and John R. Burns (2010), "Relationships among major lineages of characid fishes (Teleostei: Ostariophysi: Characiformes), based on molecular sequence data," Molecular Phylogenetics and Evolution, Vol. 54, No. 2 (February 2010).
Mirande, J. Marcos (2009), "Weighted parsimony phylogeny of the family Characidae (Teleostei: Characiformes)," Cladistics, Vol. 25, No. 6 (July 2009).
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