page_title: Arapaima
section_title: Morphology
hierarchical_section_title: Arapaima / Morphology
caption_attribution_description: English: An arapaima, pirarucu, or paiche (Arapaima leptosoma), a South American tropical freshwater fish. Photo in Sevastopol, Ukraine, zoo aquarium. Русский: Арапайма (лат. Arapaima leptosoma) — пресноводная рыба в Морском аквариуме города Севастополя Latina: Arapaima leptosoma
context_page_description: The arapaima, pirarucu, or paiche is any large species of bonytongue in the genus Arapaima native to the Amazon and Essequibo basins of South America. Genus Arapaima is the type genus of the family Arapaimidae. They are among the world's largest freshwater fish, reaching as much as 3 m. They are an important food fish. They have declined in the native range due to overfishing and habitat loss. In contrast, arapaima have been introduced to several tropical regions outside the native range, where they are sometimes considered invasive species. Its Portuguese name, pirarucu, derives from the Tupi language words pira and urucum, meaning "red fish".
  Arapaima was traditionally regarded as a monotypic genus, but later several species were distinguished. As a consequence of this taxonomic confusion, most earlier studies were done using the name A. gigas, but this species is only known from old museum specimens and the exact native range is unclear. The regularly seen and studied species is A. arapaima, although a small number of A. leptosoma also have been recorded in the aquarium trade.
context_section_description: Arapaima can reach lengths more than 2 m (6 ft 7 in), in some exceptional cases even exceeding 2.6 m (8 ft 6 in) and over 100 kg (220 lb). The maximum recorded weight for the species is 200 kg (440 lb), while the longest recorded length verified was 3.07 meters (10 ft 1 in). However, anecdotal reports suggest that Specimens as long as 4.57 meters (15 ft 0 in) exist. But verification is deemed impossible, and thus considered questionable. As a result of overfishing, large arapaima more than 2 m (6 ft 7 in) are seldom found in the wild.
  The arapaima is torpedo-shaped with large blackish-green scales and red markings. It is streamlined and sleek, with its dorsal and anal fins set near its tail.
  Arapaima scales have a mineralised, hard, outer layer with a corrugated surface under which lie several layers of collagen fibres in a Bouligand-type arrangement. In a structure similar to plywood, the fibres in each successive layer are oriented at large angles to those in the previous layer, increasing toughness. The hard, corrugated surface of the outer layer, and the tough internal collagen layers work synergistically to contribute to their ability to flex and deform while providing strength and protection—a solution that allows the fish to remain mobile while heavily armored. The arapaima has a fundamental dependence on surface air to breathe. In addition to gills, it has a modified and enlarged swim bladder, composed of lung-like tissue, which enables it to extract oxygen from the air.
caption: Arapaima leptosoma shown at its full length
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