Oxydoras niger, the ripsaw catfish or cuiu cuiu, is a species of thorny catfish native to the Amazon, Essequibo and São Francisco basins in Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru and Venezuela. It is the largest member of the Dorididae family. This species grows to a length of 100 centimetres (39 in) SL and weighs up to 13 kilograms (29 lb). This species is a minor component of local commercial fisheries. It has lateral thorns that can damage any potential predator or handler. It feeds by shifting through sand and detecting edible items with the taste receptors in the roof and floor of its mouth.

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