New Species of Giant Fish Arapaima Discovered in Brazil

Prof Donald Stewart from Department of Environmental and Forest Biology at State University of New York has described a new species of arapaima from the central Amazon of Brazil.

Arapaima leptosoma (adapted from Donald Stewart, Copeia 2013; background: the Meyers).

Arapaima leptosoma (adapted from Donald Stewart, Copeia 2013; background: the Meyers).

Arapaima, one of the world’s biggest freshwater fish and the largest freshwater fish of South America, is unique among fish – it can breathe air. The largest specimens can reach more than 2.5 m in length and weigh up to 200 kg.

Arapaima is torpedo-shaped with large scales and red markings. It is streamlined and sleek, with dorsal and anal fins set back near its tail.

The newly discovered arapaima, named Arapaima leptosoma, is the first new species to be described since 1847.

The specific name leptosoma derives from the Greek leptos (slender) and soma (body), in reference to the relatively slender body form of this species.

The new species is “distinguished from all other Arapaima by following three characters: dorsalmost lateralis sensory cavity on preopercle extremely slender; ventrolateral margin of head where third infraorbital meets anterior limb of preopercle strongly angled such that ventral surface of head is almost flat; and anterior third of dorsal-fin base covered with an enlarged, thickened sheath that hides anterior dorsal-fin rays when adpressed,” Prof Stewart described the new species in a paper published in the journal Copeia.

The only known specimen of Arapaima leptosoma was caught in 2001 near the confluence of the Solimões and Purus rivers in Amazonas State, Brazil.

“Collecting adult Arapaima involves considerable difficulties, both with logistics in the field and subsequent storage in museums,” Prof Stewart wrote in the paper.

“As this study demonstrates, however, collecting at least a few voucher specimens can greatly enhance our knowledge of these fascinating fishes. Many more are needed.”

“Arapaima have high economic, cultural, and scientific value, but their diversity has been overlooked for too long,” the scientist concluded.

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Bibliographic information: Donald J. Stewart. 2013. A New Species of Arapaima (Osteoglossomorpha: Osteoglossidae) from the Solimões River, Amazonas State, Brazil. Copeia, vol. 2013, no. 3, pp. 470-476; doi: 10.1643/CI-12-017