Lungfishes

Lungfishes, or Dipnoi, are a small order of freshwater fishes that belong to the lobe-finned (sarcopterygian) lineage. They are notable for their lungs, which enable them to breathe air, and for their relationship to the tetrapods that later colonized land. Their anatomy also includes fleshy, lobed pectoral and pelvic fins.

Extant lungfishes are represented by three genera: Neoceratodus (Australian lungfish, N. fosteri), Lepidosiren (South American lungfish, L. paradoxa), and Protopterus (African lungfishes, including several species). They inhabit tropical to subtropical freshwater systems in Australia, Africa, and South America. The fossil record contains many more lungfish species dating back to the Paleozoic.

Anatomically, lungfishes have gills throughout life and respiratory surfaces in one or two lungs for air-breathing. They retain robust lobed fins that resemble limbs and can use these fins to maneuver on the bottom.

Lungfishes are typically aquatic, living in rivers, lakes, and floodplains, often in habitats prone to drought. They feed on a variety of organisms, including aquatic invertebrates and small fish. During dry periods, some African lungfishes estivate in mucus cocoons to survive out of water.

Reproduction is generally oviparous, with eggs laid in water and fertilization occurring externally. Juveniles hatch and grow into air-breathing adults. The limb-like fins and other features highlight their place among the closest living relatives of tetrapods.

Conservation and significance: Lungfishes are of major evolutionary interest and remain sensitive to environmental changes; some species are threatened by habitat loss and water extraction, while others remain relatively common in their native ranges.