species of electric fishes (Gymnotiformes) inhabit the Amazon basin. River stingrays (Potamotrygonidae) are also known. The bull shark (Carcharhinus leucas) has been reported up the Amazon River at Iquitos in Peru. Butterflies Microbiota 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 Actinomycetota, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria and Thermoproteota. Major tributaries The Amazon has over 1,100 tributaries, twelve of which are over long. Some of the more notable ones are: Branco Casiquiare canal Caquetá Huallaga Putumayo (or Içá River) Javary (or Yavarí) Juruá Madeira Marañón Morona Nanay Napo Negro Pastaza Purús Tambo Tapajós Tigre Tocantins Trombetas Ucayali Xingu Yapura List of major tributaries The main river and tributaries are (sorted in order from the confluence of Ucayali and Marañón rivers to the mouth): List by length () – Amazon, South America – Madeira, Bolivia/Brazil – Purús, Peru/Brazil – Japurá or Caquetá, Colombia/Brazil – Tocantins, Brazil – Araguaia, Brazil (tributary of Tocantins) – Juruá, Peru/Brazil – Rio Negro, Brazil/Venezuela/Colombia – Tapajós, Brazil – Xingu, Brazil – Ucayali River, Peru – Guaporé, Brazil/Bolivia (tributary of Madeira) – Içá (Putumayo), Ecuador/Colombia/Peru – Marañón, Peru – Teles Pires, Brazil (tributary of Tapajós) – Iriri, Brazil (tributary of Xingu) – Juruena, Brazil (tributary of Tapajós) – Madre de Dios, Peru/Bolivia (tributary of Madeira) – Huallaga, Peru (tributary of Marañón) List by inflow to the Amazon See also Amazon natural region Peruvian Amazonia Notes References Bibliography External links Information on the Amazon from Extreme Science A photographic journey up the Amazon River from its mouth to its source Amazon Alive: Light & Shadow documentary film about the Amazon river Amazon River Ecosystem Research on the influence of the Amazon River on the Atlantic Ocean at the University of Southern California Amazon basin Amazon rainforest Upper Amazon Rivers of South America International rivers of South America Rivers of Colombia Rivers of Peru Colombia–Peru border Rivers of Amapá Rivers of Amazonas (Brazilian state) Rivers of Loreto Region Rivers of Pará