Two years ago, in the ocean off the coast of Palau, scientist Jiro Sakaue was scuba diving when he entered a cave. Near the ground, he saw a strange creature that looked unlike any he’d ever seen before. He collected the animal and took it back to the lab, sharing it with Hitoshi Ida, another researcher. The two were confused—it looked like an eel, but it had several features they’d never seen before. After a lengthy analysis, during which they worked with Smithsonian icythologist Dave Johnson and others, the team released their findings yesterday. The eel is the only known member of an entirely new genus and species: Protoanguilla palau, shown in this video.
In the article, the team calls its find a “living fossil” because the eel most closely resembles fossil specimens rather than any living eels. It also displays some ancient characteristics that aren’t present even in eel fossils. “There are features that make it primitive with respect to all living eels, and a couple of things that make it primitive with respect to all eels including the Cretaceous forms, which go back a hundred million years,” says Johnson, who was the lead author of the paper.
P. palau has fewer vertebrae than typical eels and an upper jaw bone that is usually only found in other types of fish, among other features. At first, the team was unsure if the creature was truly an eel, but analysis of both the bodies and the DNA makeup of the ten specimens collected confirmed they were. Because it’s most similar to eels living way back in the early Mesozoic, roughly two hundred million years ago, P. palau has a distinct evolutionary lineage, and thus its own family too, Protoanguillidae.
For the researchers, the find was shocking. “I was at the Perth meetings of the Indo Pacific Fish Conference two years ago, and Hitoshi approached me at the meetings like a man with a dirty picture,” says Johnson, describing how he was recruited to join the team. “The equivalent of this primitive eel, in fishes, has perhaps not been seen since the discovery of the coelacanth in the late 1930s,” Johnson said in a blog post published by the Natural History Museum.
Why did it take so long to find P. palau? Johnson says that, although the area is a popular dive spot, not many divers enter the caves and look closely enough to notice the limited number of eels present. Even so, the find is a surprise. “It’s extraordinary that this is the only place this has ever been found,” he says. Because the eels’ larvae can survive for up to three months at sea, he speculates that the small cave is not their only home. “I think what we’re probably dealing with is a habitat that happens to be barely accessible to divers, but there are probably other habitats that are deeper.”
The discovery is sure to intrigue not only researchers, but poachers. According to Johnson, some rare fish can go for as much as $10,000 on the black market. He says, “Imagine, a living fossil eel, which is actually a very beautiful fish, you can imagine there’s going to be some interest.” Researchers are already gathering data to determine if it should belong on the endangered species list. “We’re going to have to be careful about protecting it,” Johnson says.