Astronotus ocellatus is a species of fish from the cichlid family known under a variety of common names including oscar, tiger oscar, velvet cichlid, or marble cichlid.[1] In South America, where the species naturally resides, A. ocellatus specimens are often found for sale as a food fish in the local markets.[2][3] The fish introduced to other areas, including China, Australia, and the United States. It is considered a popular aquarium fish in the U.S
Taxonomy
The species was originally described by Louis Agassiz in 1831 as Lobotes ocellatus, as he mistakenly believed the species was marine; later work assigned the species to the genus Astronotus.[7] The species also has a number of junior synonyms: Acara compressus, Acara hyposticta, Astronotus ocellatus zebra, and Astronotus orbiculatus.Description
A. ocellatus examples have been reported to grow to about 45 cm (18 in) in length and 1.6 kilograms (3.5 lb) in weight.[1] The wild-caught forms of the species are typically darkly coloured with yellow-ringed spots or ocelli on the caudal peduncle and on the dorsal fin.[5] These ocelli have been suggested to function to limit fin-nipping by piranha (Serrasalmus spp.), which co-occur with A. ocellatus in its natural environment.[7][9] The species is also able to rapidly alter its colouration, a trait which facilitates ritualised territorial and combat behaviours amongst conspecifics.[10] Juvenile oscars have a different colouration from adults, and are striped with white and orange wavy bands and have spotted heads.
Distribution and habitat
A. ocellatus is native to Peru, Ecuador, Colombia, Brazil, and French Guiana, and occurs in the Amazon River basin, along the Amazonas, Içá, Negro, Solimões, and Ucayali River systems, and also in the Approuague and Oyapock River drainages.[1][2] In its natural environment, the species typically occurs in slow-moving white-water habitats, and has been observed sheltering under submerged branches.[5] Feral populations also occur in China,[11] northernAustralia,[12] and Florida, USA[13] as a byproduct of the ornamental fish trade. The species is limited in its distribution by its intolerance of cooler water temperatures, the lower lethal limit for the species is 12.9°C (55.22°F).
Reproduction
Although the species is widely regarded as sexually monomorphic,[5] males have been suggested to grow more quickly,[citation needed] and in some naturally occurring strains, males are noted to possess dark blotches on the base of their dorsal fins.[6][7] The species reaches sexual maturity around one year of age,[citation needed] and continues to reproduce for 9-10 years.[citation needed] Frequency and timing of spawning may be related to the occurrence of rain.[15] A. ocellatus fish are biparental substrate spawners, though detailed information regarding their reproduction in the wild is scarce.
In captivity, pairs are known to select and clean generally flattened horizontal or vertical surfaces on which to lay their 1,000 to 3,000 eggs.[citation needed] Like most cichlids, A. ocellatus practices brood care, although the duration of brood care in the wild remains unknown.
Territorial behavior
Oscars will often lay claim to an area of the aquarium and will be very aggressive towards other fish encroaching on their newly establishedterritory inside the aquarium or lake. The size of the territory varies depending on the size and aggressiveness of the fish based on its surroundings. Once the oscar establishes a territory, it will vigorously defend it by chasing away other fish.[21]
Varieties
A number of ornamental varieties of A. ocellatus have been developed for the aquarium industry. These include forms with greater intensity and quantities of red marbling across the body, albino, leucistic, andxanthistic forms. A. ocellatus with marbled patches of red pigmentation are sold as red tiger oscars, while those strains with mainly red colouration of the flanks are frequently sold under the trade name of red oscars.[22] The patterning of red pigment differs between individuals; in the United Kingdom, one A. ocellatus reportedly had markings that resembled the Arabic word for "Allah".[23] In recent years long-finned varieties have also been developed. The species is also occasionally artificially coloured by a process known as painting.
No comments:
Post a Comment