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.


  1. Laurie
    March 23, 9:52 pm

    Hi. I too love aquariums. Arapaima are beautiful fish. I saw a River Monsters episode that featured these fish. Ever since, I have been looking up anything I can find about them online, including zoos and large aquarium facilities that may house them. I was pleased to find that there are conservation efforts being made.

  2. anonamous
    December 23, 2014, 1:09 pm

    heshan, really what think he brought fish up, to understand them that’s why!

  3. Charitha Heshan
    United States
    August 17, 2014, 2:58 pm

    Hello Brian,im an aquarist and i love everything about fish and nature also its a great article. Could you tell me why that stewert guy killed those two arapaimas in the name of science. I thought he a conservationist ,i think these science people got their priorities wrong. these fish are declining in numbers and it takes years for them to reach sexual maturity to start reproducing.Two fish in the photo looks very young. I would understand if the villagers eat them,but for “educated” like stewert its just not that smart ,innit?


  4. cj campbell
    November 18, 2013, 4:35 pm

    wasn’t the Arapaima leptosoma in river monsters s.4 ep.8

  5. cj campbell
    November 18, 2013, 4:32 pm

    im 17 years old and i love studying fish cant wait tl learn more about Arapaima leptosoma

  6. zak
    November 5, 2013, 8:49 pm

    What type of freshwater fish is this… is it a new species… a fish with a tusks?

    • Brian Clark Howard
      November 6, 2013, 10:29 am

      Interesting, thanks for the tip! Not sure.

  7. El Gabilon
    October 16, 2013, 9:48 pm

    We take exception to “new species”! It is not a new species, it a species that has been previously unknown to humans. Mr. Stewarts actions are to be applaued. However, this also indicates that scientists are still sitting on their hands rather than going out and finding previously unknown species, and, at the same time attempting to discredit someone who does. Scientists like politicians need to get over their tender egos and concentrate on science without concentrating on how this will look for them in the future. Science has much to be proud of but also a lot to be ashamed of…eg., the development of the atomic bomb, refusal to get rid of small pox samples, and failing to warn, sternly enough the consequences of pollution on land, sea, air, and now space.

  8. Alexandre B Silva
    October 16, 2013, 8:14 pm

    This Pirarucu is well known in Brasil and because of its habits, size and delicious meet have been hunted almost untill extinction. Now a pisciculturist has developed techniques to raise it in farms. Full version here:

    October 16, 2013, 10:43 am

    As a biologist, I have never understood this race for dusting off museum specimens and renaming them just for the sake of publishing an article. Clearly, protection for these animals is and has been a struggle for too long, and probably continue to fail. It doesn’t reach the general public really, and efforts on physiology and ecological studies are shadowed. “needs to be collected and studied”? how about it just needs to be observed first. It’s like reorganizing your socks’ drawer and saying, hey! these are formal socks, not jogging socks. Helps no one if you have to identify a species only by killing and dissecting instead of spotting them in the wild and following behavior, ecology, etc, without too much intervention. We are that point when we have to focus efforts, instead of just coming out with new species to justify going fishing.

  10. rebecca
    October 16, 2013, 8:16 am

    It’s very good article,but why there are many spelling mistakes in it?

  11. Steve Henrich
    October 16, 2013, 1:46 am

    lets split hairs,…. Scientific names ARE in Latin,…. the thing with LAtin tho’ is that Greek is it’s root. Ancient Greek in any case. Languages DO evolve too! But then thats the subject of a different article correct?

  12. Amanda Prestes
    Manaus, Amazonas, Brasil
    October 15, 2013, 3:36 pm

    Aqui no Brasil é o famoso Pirarucu (Arapaima gigas).
    Here in Brazil it is called Pirarucu.


  13. hugg
    October 15, 2013, 9:04 am

    that thang huge

  14. Miriam ward
    October 15, 2013, 4:44 am

    Interesting article!
    Sorry to add one other error catch: it’s Ukraine, not “the” Ukraine. Think of it like France, not “the” France and it will sound more normal.

  15. Richmond
    October 14, 2013, 3:00 am

    But, aren’t scientific names traditionally written in Latin?

  16. John Henry
    October 14, 2013, 12:47 am

    that’s so cool!!!!

  17. alkis
    October 13, 2013, 6:17 pm

    leptosoma ia actually a greek word meaning thin body

  18. Dimitrios Pantazis
    North Vancouver Canada
    October 13, 2013, 1:59 pm

    The name given to this new species of fish is not Latin it is Greek lepto means thin or slim and soma means body.Other than this minor error an interesting article nonetheless.

    • Brian Clark Howard
      October 13, 2013, 10:58 pm

      Ah ok cool, thanks, I took out Latin reference.