The researchers sequenced the entire genome of the endangered Australian lungfish (Neoceratodus forsteri).
The Australian lung is also the species with the largest known animal genome, 14 times the size of a human.
To do this, it takes new DNA sequencing techniques and enormous computing power to bring together 43 billion nucleotides.
“When you look at things from a genomic perspective, the lungfish is genetically between fish and terrestrial vertebrates,” said biologist Siegfried Schloissnig of the Institute for Molecular Pathology (IMP) in Austria.
Of the six lung species still alive, four are found in Africa, one in South America, and one in Australia. They first appeared in the fossil record 400 million years ago.
This Australian lungfish retains its most ancestral traits and was erroneously classified as an amphibian when it was first discovered, due to its odd mix of fish and newts, including fins. The singularity resembles its paws. The strange “living fossils” between these species can live up to 100 years.
The Australian lungfish retains the almost fossilized characteristics of its now extinct ancestors of 100 million years ago.
The giant Australian lungfish genome contains clues to how animals make the transition from aquatic to terrestrial.
The researchers even identified the same genes responsible for our embryonic development already in lungfish, as well as the arm bones and the genes that code for them. Tetrapod-forming genes like hox-c13 and sal1 have never been seen before in fish.
Such novelties may have caused lobed finfish to conquer land, suggesting that the lung fish genome may contribute to a better understanding of this important transition in the process, the team said.
Researchers have also discovered major additions to the genes of lung fish related to smell. These genes code for odor receptors in the air, while odor receptors in water are narrowed.
Many of the extra genes that make up their giant genomes come from transcribed pieces of DNA. Some fish chromosomes contain as many nucleotides as our entire genome.
This form of genomic expansion across these copies is known to be an important driving force in evolution, with evidence to help provide organisms with the ability to adapt rapidly to changing environments.
Australia’s lungs are currently threatened by human activities that are altering their freshwater habitats. This species hunts frogs, worms, and snails, as well as gnawing aquatic plants. It usually relies on the gills to breathe, but the unique lung also allows fish to float on the surface to find fresh air when drought conditions reduce their aquatic environment.
“There is no doubt that the newly decoded genome of Australian lungs will reveal more secrets about this strange vertebrate in the future. It may not only teach us things. From an adaptation to terrestrial life which could also explain how some genomes have evolved into it. large, ”said Elly Tanaka, IMP cell geneticist.
