Lepidosiren

Lepidosiren is a genus of lungfish in the family Lepidosirenidae. It contains a single living species, Lepidosiren paradoxa, commonly known as the South American lungfish. These fishes are native to tropical South American freshwater systems, mainly in the Amazon and Orinoco basins, where they inhabit slow-moving rivers, floodplains, and seasonally flooded forests.

They reach up to about 1 meter in length, with an elongated, eel-like body, a broad rounded snout, small eyes, and fleshy lobed pectoral and pelvic fins. The dorsal and anal fins are long and continuous with the tail. Like other lungfishes, L. paradoxa possesses both gills and a pair of lungs, enabling them to breathe air.

They can survive in waters with low dissolved oxygen by breathing air at the surface. They are well known for their ability to aestivate in mud during dry seasons, forming a mucus cocoon that protects them for several months.

Lepidosiren paradoxa is primarily carnivorous, feeding on invertebrates, crustaceans, and small fish. They are mostly nocturnal or crepuscular, spending much of the day buried in mud or vegetation.

Reproduction occurs in the rainy season; eggs are laid in water and fertilization is external. Larvae hatch with gills, and lungs develop as they grow; detailed reproductive behavior is not extensively documented.

Lepidosiren is monotypic and is assessed as Least Concern on the IUCN Red List. Its broad distribution in major river systems and tolerance of hypoxic conditions contribute to its status, though local populations can be affected by habitat loss, pollution, and overfishing.

As a member of the lungfishes, Lepidosiren provides important insights into the evolution of lungs and lobed fins, representing an ancient lineage within Sarcopterygii.