The lungfish is an ancient freshwater creature, often referred to as a “living fossil” because its lineage has remained relatively unchanged for nearly 400 million years. Found in regions of Africa, South America, and Australia, these animals possess a specialized adaptation: a modified swim bladder that functions as a true lung, allowing them to breathe atmospheric air. This pulmonary capability is central to the lungfish’s resilience, enabling it to inhabit stagnant, oxygen-poor waters and survive prolonged periods of drought. The longevity of the lungfish is a direct result of these deep-seated biological adaptations.
Species and Maximum Recorded Lifespans
The longevity of lungfish varies significantly between species, particularly when comparing the African and Australian varieties. The Australian Lungfish (Neoceratodus forsteri) is recognized as the longest-lived of the six extant species, with authenticated records confirming it as a centenarian. One famous specimen, “Granddad,” lived for 84 years in captivity at the Shedd Aquarium before its death in 2017. Scientific analysis using an epigenetic aging clock estimated Granddad’s age at death to be 109 years, with a margin of error of plus or minus six years.
Another Australian Lungfish, “Methuselah,” currently residing in the California Academy of Sciences, is estimated to be over 90 years old. In the wild, Australian Lungfish are also long-lived, with typical lifespans estimated between 50 and 100 years.
African Lungfish (Protopterus species) are also very long-lived, though their maximum documented lifespans are generally shorter than their Australian counterparts. While some sources suggest they can live over 50 years in the wild, maximum confirmed longevity in captivity for a species like the West African Lungfish (Protopterus annectens) is around 18 years, with unconfirmed reports reaching up to 30 years. This difference is partly due to the African species’ reliance on a mechanism that essentially “pauses” the aging process during dry periods.
How Aestivation Contributes to Extreme Age
Aestivation, a state of dormancy analogous to hibernation but triggered by heat and drought, is the African lungfish’s secret to surviving harsh environments and achieving their impressive age. When their aquatic habitat begins to dry up, the lungfish burrows into the mud, creating a chamber where it secretes a layer of mucus that hardens into a protective cocoon. Only a small opening remains, allowing the fish to breathe air using its specialized lungs for up to several years.
The transition to aestivation involves a profound physiological shutdown, characterized by a drastic reduction in metabolic rate. The African Lungfish’s heart rate, for example, can plummet from an active rate of about 25 beats per minute down to as low as two beats per minute. This state of suspended animation conserves energy stores and minimizes the production of cellular waste, effectively slowing down the rate of biological wear and tear associated with aging.
During this period of suspended metabolism, the fish must manage the nitrogenous waste that would normally be flushed out in water as toxic ammonia. Lungfish shift their biochemistry to convert this waste into less-toxic urea, which accumulates in their tissues. This urea accumulation also helps maintain osmotic pressure and retain water within the body. By inhibiting ammonia production and converting waste to urea, the lungfish can endure without food or water until the rains return.
Environmental and Captivity Factors
The actual lifespan of a lungfish is heavily influenced by the stability of its environment, which explains the disparity between wild and captive maximum ages. In a controlled, captive environment, factors like consistent water quality, a reliable food source, and the complete absence of predators remove nearly all external mortality risks. This allows specimens to live out their full biological potential, as seen with the centenarian Australian Lungfish in aquariums.
In the wild, the African Lungfish’s longevity is directly tied to the frequency and severity of droughts, as surviving the emergence from the aestivation cocoon is a yearly risk. While adult lungfish have few natural predators, juveniles are highly vulnerable to other fish and birds, which limits recruitment into the long-lived adult population.
Habitat degradation, such as the construction of dams, also negatively impacts wild populations by blocking migration to spawning grounds and destroying the necessary nursery habitats. For the Australian Lungfish, the lack of sufficient breeding success due to habitat changes may not be immediately apparent in the long-lived adult population but eventually leads to decline. The cumulative stress of environmental fluctuations, habitat loss, and the ever-present risk of predation on younger fish means that few individuals in the wild will ever reach the extreme maximum ages recorded under the ideal conditions of a modern aquarium.