The coelacanth genome has also allowed scientists to test other long-debated questions. For example, coelacanths possess some features that look oddly similar to those seen only in animals that dwell on land, including "lobed" fins, which resemble the limbs of four-legged land animals (known as tetrapods). Another odd-looking group of fish known as lungfish possesses lobed fins too. It is likely that one of the ancestral lobed-finned fish species gave rise to the first four-legged amphibious creatures to climb out of the water and up on to land, but until now, researchers could not determine which of the two is the more likely candidate.
In addition to sequencing the full genome nearly 3 billion "letters" of DNA from the coelacanth, the researchers also looked at RNA content from coelacanth (both the African and Indonesian species) and from the lungfish. This information allowed them to compare genes in use in the brain, kidneys, liver, spleen and gut of lungfish with gene sets from coelacanth and 20 other vertebrate species. Their results suggested that tetrapods are more closely related to lungfish than to the coelacanth.
However, the coelacanth is still a critical organism to study in order to understand what is often called the water-to-land transition. Lungfish may be more closely related to land animals, but its genome remains inscrutable: at 100 billion letters in length, the lungfish genome is simply too unwieldy for scientists to sequence, assemble, and analyze. The coelacanth's more modest-sized genome (compara
|Contact: Haley Bridger|
Broad Institute of MIT and Harvard