New Species of Giant Air-Breathing Fish: Freshwater Species of the Week

New species of arapaima
These three fish in an aquarium in the Ukraine actually belong to a newly identified species of arapaima, a giant, air-breathing dweller of the Amazon. Photo: George Chernilevsky, Wikimedia Commons

Water Currents previously reported on Donald Stewart‘s ongoing efforts to reclassify a giant Amazonian fish as representing several distinct species. The work of the fish biologist at the SUNY College of Environmental Science and Forestry (ESF) is supported in part by National Geographic.

freshwater species of the weekStewart’s latest work has just been published in the journal Copeia, and marks official identification of Arapaima leptosoma, the first entirely new species of arapaima since 1847.

Among the world’s largest freshwater fish, arapaimas live in tropical South America, especially Brazil and Guyana. They can grow up to 10 feet (3 meters) long and weigh 440 pounds (200 kilograms). They breathe air through a primitive lung, and tend to live in oxygen-poor backwaters.

Arapaimas have long been an important food source for Amazonian peoples. They continue to be hunted and biologists have concerns about their status, although they are not endangered.

Getting the new species named is important “because it brings attention to the diversity of arapaimas that is out there and that needs to be collected and studied,” said Stewart. “Hopefully it will get more people in Brazil looking more closely at what’s swimming around out there.”

Donald Stewart and arapaimas
Donald Stewart and arapaimas. Photo courtesy of SUNY ESF

Changing Conventional Wisdom

For a century and a half, the prevailing view among scientists had been that there was only one species of arapaima, but Stewart has shown that there are actually at least five. In March, he published a paper that renamed a species of arapaima that had been suspected in the 1800s, before scientists decided to roll it up into one species.

The newest species, Arapaima leptosoma, had not been suspected before. It is more slender than other arapaimas (it’s name leptosoma is a reference to this characteristic).

Stewart explained that the new species also has a horizontal black bar on the side of its head, which is a unique series of sensory organs.

The new species was described from a specimen kept at the Instituto Nacional de Pesquisas da Amazônia in Manaus, Brazil. That animal had been collected in 2001 near the confluence of the Solimões and Purus rivers in Amazonas State, Brazil.

Wikipedia Update Needed

Stewart noticed that two of the pictures on the Wikipedia page for arapaima actually show the new species A. leptosoma (this one and this one). Those pictures were apparently made of fish kept in a public aquarium in Ukraine.

“I don’t know how it got there, someone most be culturing them and sent them to Ukraine,” he said.

Stewart added that he suspects there may be even more species of arapaima. “We keep finding other things out there,” he said.

He has more fieldwork planned for the future to keep investigating the mysteries of this giant fish.


Brian Clark Howard covers the environment for National Geographic. He previously served as an editor for and E/The Environmental Magazine, and has written for Popular Science,,,, Yahoo!, MSN, and elsewhere. He is the co-author of six books, including Geothermal HVACGreen LightingBuild Your Own Small Wind Power System, and Rock Your Ugly Christmas Sweater.


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