Tembeassu marauna
Tembeassu marauna is a very rare electric knifefish from the upper Paraná River in Brazil. Only three specimens are known, all collected in 1965 during the construction of the Ilha Solteira dam. The fish has a knife-like body, a long head, and no dorsal or pelvic fins. Its most distinctive feature is a fleshy tip on the upper jaw containing about 15 small teeth; the lower jaw has a toothless extension. Teeth on the upper jaw number about 15 and about 30 on the lower jaw. The largest specimen measured about 19.6 cm.
It belongs to the Apteronotidae family and can generate a weak electric field to navigate and sense its surroundings. Very little is known about its natural history or why the jaw extensions exist, but they appear in both sexes, so they are probably not for reproduction. They may help with feeding, though this is not certain. T. marauna is thought to live in deep waters of large rivers.
Taxonomic history is complex. It was described in 1998 and placed in its own genus, Tembeassu. A 2005 re-examination kept it in Tembeassu rather than merging it with Apteronotus. In 2022 a second species in the genus, Tembeassu titanicus, was described from the same area and another part of the Paraná River system.
Conservation: the IUCN has not assessed Tembeassu marauna. Brazilian environmental authorities list it as critically endangered, possibly extinct, due to extensive dam-building in the Paraná region. No new specimens have been found since 1965.
This page was last edited on 2 February 2026, at 16:04 (CET).