Lacking key genes that control selfish bits of DNA, the South American lungfish’s genome just grew and grew

A species of lungfish found in South America has claimed the title of the animal with the biggest genome sequenced so far. The DNA of Lepidosiren paradoxa comprises a staggering 91 billion chemical letters or “bases,” 30 times as many as the human genome, researchers report today in Nature. However, those 91 billion bases of DNA only contain about the same number of genes that humans have—roughly 20,000—with the rest consisting of noncoding, perhaps even “junk” DNA.

By comparing this genome with those of other lungfishes, the researchers determined that L. paradoxa adds the equivalent of a human genome to its DNA every 10 million years.

This is the largest genome size reported so far in animals.