It’s hard to mistake an arapaima for anything else: these massive, heavily-armored, air-breathing fish (they have to surface every few minutes) are the megafauna of the Amazon’s rivers. But despite their unmistakability, and the fact that they have been hunted by indigenous people for millennia, scientists still know relatively little about arapaima, including just how many species there are. Since the mid-Nineteenth Century, scientists have lumped all arapaima into one species: Arapaima gigas. However, two recent studies in Copeia split the arapaimas into at least five total species—and more may be coming.
In the most recent study, researcher Donald Stewart with SUNY College of Environmental Science and Forestry (ESF), describes an entirely new species of arapaima based on a specimen held in the Instituto Nacional de Pesquisas da Amazônia in Brazil. Dubbed Arapaima leptosoma, the new species is more slender than Arapaima gigas and possesses other important physical differences.
“This species was collected near the confluence of the Solimões and Purus rivers in Amazonas State, Brazil,” Stewart writes. “It is the first new species of Arapaima to be described since 1847.”
But, Stewart proposes resurrecting an additional three arapaima species that were described at one time in the Nineteenth Century, but never fully accepted by the scientific community. For example, earlier in the year Stewart also published a paper that argues for resurrecting Arapaima agassizii that was described in 1847. The species was based on a specimen collected by a French biologist in the early 19th Century, however the specimen in question was destroyed by a bomb in World War II. Looking back at original sketches made of the now lost specimen, Stewart contends that the species is in fact distinct. However, no one knows exactly where to find Arapaima agassizii.
A new species of arapaima: Arapaima leptosoma. This species is housed at Sevastopol Sea Aquarium in the Ukraine, but long conflated with Arampaima gigas. Photo by: George Chernilevsky.
“Arapaima agassizii still is known only from the holotype [i.e. specimen], which was collected in 1817–20 somewhere in lowlands of the Brazilian Amazon,” Stewart writes in his paper. “It thus is important to locate this taxon to determine its distribution and conservation status.”
If arapaima are decidedly a number of distinct species, instead of one single type it would change the way the fish are managed and their conservation classifications. In many parts of the Amazon, arapaima were long overfished, but some populations are beginning to make a comeback due to better management and conservation work.
Arapaima are massive freshwater fish, weighing around 200-400 pounds (90-180 kilogram) and measuring 2-2.5 meters (6.5-8 feet). They are air-breathers, which helps them survive in the sometimes oxygen-depleted rivers of the Amazon; while they don’t have lungs, they have a swim bladder that has evolved to take-in oxygen. As if that weren’t enough, arapaima are armored by incredibly tough, yet flexible scales—so strong that not even piranhas can make a dent. Scientists say arapaima are virtually unchanged in the fossil record for the last 23 million years.
Close-up of arapaima at Smithsonian National Zoo. Photo by: Tiffany Roufs.
- Donald J. Stewart (2013) Re-description of Arapaima agassizii (Valenciennes), a Rare Fish from Brazil (Osteoglossomorpha: Osteoglossidae). Copeia: March 2013, Vol. 2013, No. 1, pp. 38-51.
- Donald J. Stewart (2013) A New Species of Arapaima (Osteoglossomorpha: Osteoglossidae) from the Solimões River, Amazonas State, Brazil. Copeia: September 2013, Vol. 2013, No. 3, pp. 470-476.
(07/15/2013) Let’s go back some 14,000 years (or up to 50,000 depending on who you talk to), since this is the first time humans encountered the meandering, seemingly endless river system of the Amazon. Certainly, the world’s first Amazonians would have been astounded by the giant beasts of the region, including ground sloths and mastodons (both now extinct), as well as giant anteaters, armadillos, and tapirs, currently the biggest land animal on the continent. But these first explorers might have been even more surprised by what dwelled in the rivers: anaconda, caiman, and the arapaima. Wait, the what?
(10/11/2013) In one of the most untouched and remote rainforests in the world, scientists have discovered some sixty new species, including a chocolate-colored frog and a super-mini dung beetle. The species were uncovered in Southeastern Suriname during a Rapid Assessment Program (RAP); run by Conservation International (CI), RAPS involve sending teams of specialists into little-known ecosystems to record as much biodiversity as they can in a short time. In this case, sixteen researchers from around the world had about three weeks to document the region’s biodiversity.
(09/18/2013) Four previously unknown species of legless lizard have been described in California, report researchers from the University of California at Berkeley and Cal State-Fullerton.
(09/18/2013) A ground-warbler from the Philippines is the twenty-third species of bird described in 2013.
(09/11/2013) A species of shark that uses its fins to ‘walk’ along the bottom of the ocean floor has been discovered off the coast of Indonesia. The shark, Hemiscyllium halmahera, uses its fins to wiggle along the seabed and forage for small fish and crustaceans, scientists from Conservation International said on Friday.
(08/16/2013) A new genus of fairyfly has been discovered in Costa Rica. The new species aptly named Tinkerbella nana after the fairy in J.M. Barrie’s play ‘Peter Pan’ is one of the smallest winged insects in the neotropics. Found in both temperate and tropical climates, the fairyfly is not actually a fly as its name suggests, but instead is more closely related to wasps – being classed within the superfamily Chalcidoidea, or the “chalcid wasps”.
(08/15/2013) While the olinguito looks like a wild, tree-climbing teddy bear with a cat’s tail, it’s actually the world’s newest mammalian carnivore. The remarkable discovery—the first mammal carnivore uncovered in the Western Hemisphere since the 1970s—was found in the lush cloud forests of the Andes, a biodiverse region home to a wide-range of species found no-where else. Dubbed the olinguito (Bassaricyon neblina), the new mammal is a member of a little-known, elusive group of mammals—olingos—that are related to raccoons, coatis, and kinkajous. However, according to its description in the journal Zookeys, the olinguito is the most distinct member of its group, separated from other olingos by 3-4 million years (or longer than Homo sapiens have walked the Earth).
(08/06/2013) The bushmeat markets of Lao PDR (Laos) are filled with racks of wild game harvested both legally and illegally from the surrounding landscapes. While these meat markets certainly provide local protein to patrons, for wildlife biologists they offer something more. These bizarre zoological exhibits are a rich source of information about wildlife populations and wildlife consumption in remote areas.