<Tr> <Td> </Td> <Td> This section needs expansion . You can help by adding to it . (February 2017) </Td> </Tr> <P> The anaconda is found in shallow waters in the Amazon basin . One of the world's largest species of snake, the anaconda, spends most of its time in the water with just its nostrils above the surface . Species of caimans, that are related to alligators and other crocodilians, also inhabit the Amazon as do varieties of turtles . </P> <P> The Amazonian fish fauna is the centre of diversity for neotropical fishes . 5,600 species are currently known, and approximately fifty new species are discovered each year . The arapaima, known in Brazil as the pirarucu, is a South American tropical freshwater fish, one of the largest freshwater fish in the world, with a length of up to 15 feet (4.6 m). Another Amazonian freshwater fish is the arowana (or aruanã in Portuguese), such as the silver arowana (Osteoglossum bicirrhosum), which is a predator and very similar to the arapaima, but only reaches a length of 120 centimetres (47 in). Also present in large numbers is the notorious piranha, an omnivorous fish that congregates in large schools and may attack livestock and even humans . There are approximately 30 to 60 species of piranha . However, only a few of its species are known to attack humans, most notably Pygocentrus nattereri, the red - bellied piranha . The candirú, native to the Amazon River, is a species of parasitic fresh water catfish in the family Trichomycteridae, just one of more than 1200 species of catfish in the Amazon basin . Other catfish' walk' overland on their ventral fins, while the kumakuma (Brachyplatystoma filamentosum), aka piraiba or "goliath catfish", can reach 3.6 metres (12 ft) in length and 200 kilograms (440 lb) in weight . The electric eel (Electrophorus electricus) and more than 100 species of electric fishes (Gymnotiformes) inhabit the Amazon basin . River stingrays (Potamotrygonidae) are also known . The bull shark (Carcharhinus leucas) has been reported 4,000 kilometres (2,500 mi) up the Amazon River at Iquitos in Peru . </P> <P> Freshwater microbes are generally not very well known, even less so for a pristine ecosystem like the Amazon . Recently, metagenomics has provided answers to what kind of microbes inhabit the river . The most important microbes in the Amazon River are Actinobacteria, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria and Crenarchaeota . </P>

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