As expected, the genome holds clues to the genetic changes behind the transition from a lobed fin to a tetrapod limb, Amemiya says. For example, the analysis found that coelacanths and tetrapods share a regulatory gene sequence that helps to promote limb development. But other findings came as a complete surprise. The fish is the first vertebrate found to lack genes for immunoglobulin-M, an almost universal immune-system protein. Instead, it has two genes for a distantly related immune protein that evidently “pick up the slack”, he says.
Further analysis of the genome is bound to reveal much about our own distant past, adds Noonan. “It will allow us to identify the genetic drivers of tetrapod evolution, the genes and regulatory elements that are responsible for the vertebrate land transition.”