Astronotus ocellatus is a species of fish from the cichlid family, originally described by Louis Agassiz in 1831, although he mistakenly classified it in the marine genus Lobotes. The largest of the new world cichlids, they can live 10-20 years and reach up to a maximum length of 45cm (18 inches) long, although they are most commonly found 25-30 cm (10-12 inches) in length and 1.6 kilograms (3.5 lb) in weight. A popular aquarium fish, Astronotus ocellatus has many common names, including oscar, tiger oscar, velvet cichlid, or marble cichlid, which reflect a number of bred ornamental varieties, including long-finned varieties and various color morphs. Oscars are native to the Amazon river basin, especially shallow, quiet floodplains and swamps. Native oscars usually show characteristic orange ringed, bilateral ocelli (eyespots) at the base of their tail which have been shown to dissuade predators and also function in sexual selection, as these fish are very visually oriented. Suction feeders, A. ocellatus are omnivorous, eating invertebrates such as flies, worms, crayfish, some small fish, fruit that falls into water, and large oscars will even eat small vertebrates, such as mice. Oscars are an esteemed food species in South America, although not commonly eaten elsewhere, as they grow too slowly for aquaculture. Escaped ornamentals and individuals purposely introduced into waterways have established wild populations in Asia, China and North America.
(Beeching, 1995; Froese 2011; Griffioen 1999; Nico and Fuller 2012; Robbins; Wikipedia 2012; Winemiller 1990)
These fish are found in the Amazon River basin, from the Orinoco River to the Rio Paraguay, throughout Venezuela, Guyana, and Paraguay. (The Aquarium Encyclopedia, 1983.)
Biogeographic Regions: neotropical (Native )
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: Native to Orinoco, Amazon, and La Plata river basins, South America. Established in Hawaii and southern Florida. Has been collected in Pennsylvania, Massachusetts, Maine, and Rhode Island. Introductions are due to fish farm and aquarium fish releases.
Compared to other fishes, Astronotus ocellatus has a slender, laterally compressed body, and a blunt head with a large mouth and protruding jaw. Colors vary greatly among geographic regions and individuals, but most are dark green to black, with red stripes along its back and a red circle on the base of the tail fin. The adult fish grows up to 35 cm long. Males and females are visually indistinguishable. (Gracyalny, 1996.)
Range mass: 2 to 4 kg.
Other Physical Features: bilateral symmetry
Length: 33 cm
Found in the tropical lowlands of South America, A. ocellatus prefers the floodplains and swamps of the Amazon River basin. They are most comfortable in water about 25 degrees Celsius, or slightly higher for breeding. (Kullander, 1996)
Aquatic Biomes: rivers and streams
Habitat Type: Freshwater
Comments: Florida: mud- and sand-bottomed canals and ponds (Page and Burr 1991). Eggs are laid on substrate.
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Although these predators are not at all choosy, they feed mostly on insect larvae and smaller fish. Their feeding habits require that Oscars have excellent eyesight. Because of this, they have been the subject of numerous studies concerning eyesight in fish. (The Aquarium Encyclopedia, 1983, Andison and Sivak, 1996)
Diseases and Parasites
Life History and Behavior
Perception Channels: tactile ; chemical
Though they can become much larger, A. ocellatus are sexually mature soon in life, usually by the time they are 12 cm long. These fish exhibit a high degree of parental care. After spawning in open water, the eggs are laid on a piece of ground that has been cleared by one of the parents. After three or four days, the eggs hatch. The brood is then transported to a sandy hollow for about one week. Young fish have been observed clinging to their parents with their mouths, even after they are able to swim freely. (The Aquarium Encyclopedia, 1983)
Spawns June-October at 28-33 C in Florida. Parents incubate eggs and guard young.
Molecular Biology and Genetics
Barcode data: Astronotus ocellatus
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Astronotus ocellatus
Public Records: 5
Specimens with Barcodes: 15
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NNA - Not Applicable
Rounded National Status Rank: NNA - Not Applicable
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Relevance to Humans and Ecosystems
As a popular aquarium fish, A ocellatus has some obvious economic importance to humans. Additionally, it has been used by biologists in numerous studies of fish, including studies on behavior, eyesight, auditory systems, and swim bladders.
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. In South America, where the species naturally resides, A. ocellatus specimens are often found for sale as a food fish in the local markets. The fish introduced to other areas, including China, Australia, and the United States. It is considered a popular aquarium fish in the U.S.
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. The species also has a number of junior synonyms: Acara compressus, Acara hyposticta, Astronotus ocellatus zebra, and Astronotus orbiculatus.
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. 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. 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. The species is also able to rapidly alter its colouration, a trait which facilitates ritualised territorial and combat behaviours amongst conspecifics. 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. In its natural environment, the species typically occurs in slow-moving white-water habitats, and has been observed sheltering under submerged branches. Feral populations also occur in China, northern Australia, and Florida, USA 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).
Although the species is widely regarded as sexually monomorphic, males have been suggested to grow more quickly, and in some naturally occurring strains, males are noted to possess dark blotches on the base of their dorsal fins. The species reaches sexual maturity around one year of age, and continues to reproduce for 9-10 years. Frequency and timing of spawning may be related to the occurrence of rain. 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. Like most cichlids, A. ocellatus practices brood care, although the duration of brood care in the wild remains unknown.
In the Aquarium
The oscar is one of the most popular cichlids in the aquarium hobby.
|This article is written like a manual or guidebook. (September 2014)|
Captive oscars may be fed prepared fish food designed for large carnivorous fish: crayfish, worms, and insects (such as flies, crickets and grasshoppers). Feeding live foods may increase the rate of growth but also may cause endoparasites. Poultry and/or mammalian flesh, including beefheart, should not be fed long term as these fatty foods will contribute to fatty liver disease. Since these fish eat fruit in the wild, items such as melons, oranges, and other fruits can also be used as a type of food. Just about anything that falls into the water would be eaten by oscars. Live feeder fish can be given, but fish such as goldfish and rosy red feeder minnows should not be fed. These contain an enzyme (thiaminase) within their flesh which binds vitamin B1, leading to deficiency. Most fish eaten by A. ocellatus in the wild are relatively sedentary catfish, including Bunocephalus, Rineloricaria, and Ochmacanthus species. The species uses a suction mechanism to capture prey, and has been reported to exhibit "laying-on-side" death mimicry in a similar fashion to Parachromis friedrichsthalii and Nimbochromis livingstonii. The species also has an absolute requirement for vitamin C, and develops health problems in its absence.
Oscars will often lay claim to an area of the aquarium and will be very aggressive towards other fish encroaching on their newly established territory 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.
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, and xanthistic 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. 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". In recent years long-finned varieties have also been developed. The species is also occasionally artificially coloured by a process known as painting.
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- Department of primary industry and fisheries. "Noxious fish – species information". Queensland Government, Australia. Archived from the original on 2007-08-29. Retrieved 2007-03-16.
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- Kmuda. "Oscar Fish Diet". Retrieved 23 May 2012.
- Waltzek,TB and Wainwright, PC (2003). "Functional morphology of extreme jaw protrusion in Neotropical cichlids". Journal of Morphology 257 (1): 96–106. doi:10.1002/jmor.10111. PMID 12740901.
- Tobler, M. (2005). "Feigning death in the Central American cichlid Parachromis friedrichsthalii". Journal of Fish Biology 66 (3): 877–881. doi:10.1111/j.0022-1112.2005.00648.x.
- Gibran,FZ. (2004). Armbruster, J. W., ed. "Dying or illness feigning: An unreported feeding tactic of the Comb grouper Mycteroperca acutirostris (Serranidae) from the Southwest Atlantic". Copeia 2004 (2): 403–405. doi:10.1643/CI-03-200R1. JSTOR 1448579.
- Fracalossi, DM; Allen, ME; Nicholsdagger, DK and Oftedal, OT (1998). "Oscars, Astronotus ocellatus, Have a Dietary Requirement for Vitamin C". The Journal of Nutrition 128 (10): 1745–1751. PMID 9772145.
- "Oscar Fish Lover". OFL. Retrieved 19 May 2013.
- Sandford, Gina; Crow, Richard (1991). The Manual of Tank Busters. USA: Tetra Press. ISBN 3-89356-041-6.
- BBC News (2006-01-31). "Tropical fish 'has Allah marking'". BBC, UK. Retrieved 2007-03-18.
- Mike Giangrasso. "Death by Dyeing – dyed fish list". Death by Dyeing.org. Retrieved 2007-03-18.
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