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Lungfish (subclass Dipnoi)

FishLiving fossilAir-breather

Australian lungfish (Neoceratodus forsteri), a heavy-bodied fish with fleshy fins.

Australian lungfish (Neoceratodus forsteri).

Image: Jstuby, CC0, via Wikimedia Commons.

Overview

Lungfish (subclass Dipnoi) are ancient freshwater fish famous for an extraordinary ability: they can breathe air using true lungs. Survivors of a lineage that goes back hundreds of millions of years, they are often called “living fossils,” and they hold a special place in evolution as close relatives of the lobe-finned fish from which land vertebrates ultimately descended. The Australian lungfish (Neoceratodus forsteri), shown here, is the most primitive of the living species, with a single lung and large, overlapping scales.

Six species survive today, in Africa, South America, and Australia, and several can gulp air at the surface to survive in warm, stagnant, oxygen-poor water that would suffocate ordinary fish.

Note: details here cover lungfish broadly, with the Australian lungfish as a reference; habits differ between species. Treat general statements as approximate and verify against authoritative sources.

Habitat & Range

Lungfish live in fresh water — rivers, lakes, swamps, and floodplains — in Africa, South America (the Amazon and Paraguay basins), and eastern Australia, depending on the species. Many inhabit warm, slow, or seasonally drying waters where the ability to breathe air is a huge advantage. The Australian lungfish keeps to permanent rivers and pools.

Diet

Lungfish are mostly carnivores and omnivores, eating molluscs, crustaceans, worms, insects, small fish, and amphibians, plus some plant matter in certain species. They have strong, plate-like crushing tooth structures suited to grinding hard-shelled prey, and they forage slowly along the bottom.

Behavior

The lungfish's signature trait is air-breathing: most rise to the surface to gulp air into their lung(s), letting them live where dissolved oxygen is scarce — and the African and South American lungfish actually depend on breathing air, drowning if kept from the surface. Most remarkable is how some African lungfish survive drought: as their water dries up, the fish burrows into the mud and forms a slime-and-mud cocoon, slows its body right down (a dormant state called aestivation), and can survive for months — even years — until rains return. The Australian lungfish does not do this and breathes air only when needed.

Human Interaction & Conservation

Lungfish are of huge scientific interest for what they reveal about the evolution of air-breathing and the move of vertebrates onto land. They are caught for food in parts of Africa and South America, and the Australian lungfish is a legally protected species of conservation concern, sensitive to river alteration. Consult authoritative sources for species-specific status.

More photos of the lungfish

A lungfish showing its large overlapping scales and paddle-like fins.

Australian lungfish (Neoceratodus forsteri).

Image: Mitch Ames, CC BY-SA 4.0, via Wikimedia Commons.

Frequently Asked Questions — Lungfish

Can lungfish really breathe air?
Yes — that's their defining feature. Lungfish have true lung(s) and rise to the surface to gulp air, which lets them live in warm, stagnant, low-oxygen water that would suffocate most fish. The African and South American lungfish even depend on air-breathing and will drown if they can't reach the surface, while the Australian lungfish breathes air mainly when oxygen runs low.
How do lungfish survive when their water dries up?
Some African lungfish burrow into the mud as their pool dries, wrap themselves in a cocoon of mucus and mud, and enter a dormant state called aestivation, slowing their metabolism dramatically. In this mud cocoon they can survive for months — sometimes years — without water, reviving when the rains return and refill their habitat.
Why are lungfish important to evolution?
Lungfish are close living relatives of the lobe-finned fish from which the first land vertebrates evolved, and they retain ancient features including air-breathing lungs. Studying them helps scientists understand how backboned animals made the transition from water to land, which is why lungfish are prized 'living fossils.'
Where do lungfish live?
In fresh water across three continents: Africa, South America, and Australia. The six living species include several African lungfish, the South American lungfish, and the Australian lungfish, living in rivers, lakes, swamps, and floodplains — often in warm or seasonally drying waters where breathing air is a real advantage.

Sources and further reading

Authoritative wildlife references used for general educational context. Conservation status should always be verified against current IUCN Red List data. External links open in a new tab.