Lepidosiren paradoxa, locally known as pirambóia, belongs to the order Dipnoi, or true lungfi shes. Th is group includes two other genera: a single Australian species of Neoceratodus (N. forsteri) and at least four African species of Protopterus (Protopterus aethiopicus, P. amphibius, P. annectens, and P. dolloi). Lungfi shes are members of an ancient group of bony fi shes, the Sarcopterygii or lobe-fi nned fi shes, which were widespread during the Devonian period. Since the expedition of Carter and Beadle in the year 1931, it has been known that the pirambóia dig burrows and aestivate during low water periods. Th e black body of this lungfi sh is very elongated, with two pairs of lobe fi ns, fi ve gill arches; its length can go upto 1.5 m, it moves slowly and lives in swampy areas. Th is chapter describes the main characteristics of the South American lungfi sh, Lepidosiren paradoxa, and, when necessary, compares it to other lungfi shes or teleosts, such as Arapaima and

Symbranchus that have similar biological or ecological traits. Th e chapter is divided into sections where general conditions of living dipnoan genera are compared, and the main characteristics of South American lungfi sh distribution and habitat, aestivation, reproductive, and feeding behavior are reviewed. Additionally, some metabolic adaptations are described, reviewing the literature and discussing some new facts that were studied in our laboratories. Keywords: Lepidosiren, Amazon, DNA content metabolic adjustments, behavior.