South American Lungfish Genome Is World’s Largest
The 91-billion base pair sequence reveals how runaway genetic expansion shapes the evolution of ancient fish.
Updated on Oct. 30, 2026 in Life Sciences
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In a 2024 study, researchers sequenced the genome of the South American lungfish, identifying it as the largest in the animal kingdom at 91 billion base pairs. This expansive genome is 30 times larger than the human genome and consists of 90 percent repetitive DNA sequences.
Why it matters
Understanding this genomic expansion clarifies the evolutionary mechanisms that allow some species to accumulate vast amounts of DNA while others maintain smaller genomes. The study highlights how a reduction in regulatory controls allows for the unchecked spread of genetic elements over millions of years.
The South American lungfish genome contains 91 billion base pairs, dwarfing the 40 billion in the West African species and 43 billion in the Australian variant. Roughly 90 percent of this total is comprised of repetitive DNA sequences.
The players
South American lungfish
An ancient species of lobe-finned fish that serves as a living link to the ancestors of land-dwelling vertebrates.
Nature
A preeminent multidisciplinary scientific journal that publishes high-impact peer-reviewed research across all areas of science.
The details
The massive genome size results from an accumulation of transposons — mobile genetic elements that copy themselves and insert into new locations within a genome. Researchers found that lungfish lack sufficient levels of piRNAs (piwi-interacting RNAs), which are small RNA molecules that normally suppress the activity of these transposons. Without this regulatory restraint, the genome expanded by the equivalent of an entire human genome every 10 million years over the last century.
Timeline
380 million to 360 million years ago: Lobe-finned fish moved onto land during the late Devonian period.
2019: Research was published regarding ecological constraints and genome size.
2024: The study on lungfish genome sequencing was published in Nature.
The Tech Race
This sequencing effort establishes a new benchmark for genome size in the animal kingdom, significantly surpassing the 48 billion base pairs found in the Antarctic krill. It advances the ongoing biological race to catalog the extreme diversity in genetic architecture across vertebrate species.
This research provides a fundamental reference for scientists studying vertebrate evolution and the mechanics of genome regulation. It does not offer immediate applications for consumer technology or clinical medicine.
The takeaway
The South American lungfish reveals the extreme limits of genomic expansion in the absence of robust transposon suppression. Scientists can now watch for comparative studies to determine if similar piRNA deficiencies exist in other large-genome organisms.
Further reading
For broader context on current discoveries in biology and genetics, explore our coverage in Life Sciences.
Source note: This article includes information reported by Discover Magazine.
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