Lungfish Amazing Facts — The Living Fish That Breathes Air and Has Been Doing So for 400 Million Years

The lungfish is one of the most extraordinary living animals on Earth — a fish that breathes air through functional lungs, can survive years without water buried in dried mud, and represents one of the closest living relatives of the first vertebrates to crawl out of the water onto land over 375 million years ago. Here are the most amazing lungfish facts!

Did you know? The African lungfish can survive being completely buried in dried mud for up to four years without water, food or normal breathing — sustaining itself in a state of suspended animation called aestivation while waiting for the next rain!

🫁 A Fish With Functional Lungs

Unlike virtually all other fish, which breathe exclusively through gills, lungfish possess functional lungs — modified swim bladders that have evolved into genuine respiratory organs capable of absorbing atmospheric oxygen directly from air. In some lungfish species, breathing air is obligatory — the fish will drown if prevented from surfacing to breathe, even in well-oxygenated water. The Australian lungfish can use either gills or its single lung depending on conditions; the African and South American species rely more heavily on air breathing and cannot survive in poorly oxygenated water without surfacing. This lung-based air breathing is the direct evolutionary precursor to the lungs of all terrestrial vertebrates, including amphibians, reptiles, birds and mammals.

⏳ Surviving Four Years Without Water

The African lungfish has evolved one of the most extraordinary survival strategies of any vertebrate animal. When the seasonal rivers and pools it inhabits begin drying out during the dry season, the lungfish burrows into the mud, secretes a mucus cocoon around its body — with a small opening for breathing — and enters a state of profound metabolic depression called aestivation. In this state, the lungfish can survive for months to years until rains return — the longest confirmed aestivation periods documented in laboratory conditions extend to four years. During aestivation, the fish's metabolism drops to approximately one sixtieth of its normal rate, muscles are slowly metabolised to provide energy and the kidneys drastically reduce function to minimise water loss. When rains return and the mud becomes moist, the fish revives within minutes.

🐸 Our Closest Fish Relative

Molecular and anatomical studies have consistently found that lungfish are the closest living fish relatives of tetrapods — the group including amphibians, reptiles, birds and mammals — making them more closely related to humans than to most other fish. This extraordinary relationship reflects the evolutionary position of lungfish as near-relatives of the fish that first colonised land during the Devonian period, over 375 million years ago. The lungfish's air-breathing ability, lobed fins with internal bone structures resembling early limb bones, and various other anatomical features all reflect their position near the evolutionary transition between fish and terrestrial vertebrates — making them living witnesses to one of the most important transitions in vertebrate evolution.

🦴 Ancient and Virtually Unchanged

Lungfish are often described as "living fossils" because their body plan has remained remarkably stable for an extraordinarily long time. Fossil lungfish dating back over 400 million years are recognisably similar to their modern descendants, demonstrating a rate of evolutionary change far slower than most other vertebrate groups. While their body plan has remained stable, lungfish have accumulated genetic changes over this time — the genome of the Australian lungfish is the largest of any vertebrate animal measured, at over 40 billion base pairs — approximately 14 times larger than the human genome.

🌍 Three Surviving Groups

Six surviving lungfish species are distributed in three widely separated regions — four species in Africa, one in South America and one in Australia. This geographic distribution reflects the ancient origins of lungfish, which were widespread during the Devonian period before the continents separated to their current positions. The Australian lungfish, Neoceratodus forsteri, is considered the most primitive of the surviving species, retaining more ancestral features including a single lung rather than the paired lungs of African and South American species. It is found only in two river systems in Queensland, Australia, and is listed as Vulnerable.

🐊 Surviving Shared Habitats With Crocodiles

African lungfish share their river and swamp habitats with Nile crocodiles, and the relationship between the two is surprisingly straightforward — large crocodiles regularly eat lungfish when they can catch them. The lungfish's primary defence against crocodile predation is its ability to burrow into mud and aestivate when water levels drop — retreating to a hiding place that crocodiles cannot easily access. In some regions, local fishermen locate and harvest aestivating lungfish by digging into dried mud along former riverbeds during the dry season — a traditional fishing practice possible only because of the lungfish's extraordinary survival strategy.

Amazing final fact: Lungfish can live for extraordinarily long periods — the Australian lungfish specimen named "Granddad," kept at the Shedd Aquarium in Chicago from 1933 until his death in 2017, was believed to be at least 84 years old at the time of his death, and may have been considerably older. This exceptional longevity, combined with a genome 14 times larger than a human's, makes the lungfish one of the most biologically extraordinary vertebrate animals currently known to science.

Ancient, air-breathing and capable of waiting four years for rain, the lungfish is living proof that some of evolution's most extraordinary solutions were developed hundreds of millions of years ago and have never needed improving. 🐟

All content written originally by Geeta Singh. 

Sources & Further Reading: Information researched from  Wikipedia (en.wikipedia.org), National Geographic, Nature Journal, Australian Museum.