What’s the News: Biologists have discovered an eel so bizarre that they didn’t initially know if it was an eel or some other kind of fish. The strange creature, dubbed Protoanguilla palau after a researcher found it in an undersea cavern off the coast of Palau
, has very few of the anatomic features of modern eels, but displays many hallmarks of primitive eels from the Mesozoic era
. It appears that the eel’s last common ancestor with any other living creature existed 200 million years ago, the researchers report in the journal Proceedings of the Royal Society B
. How the Heck:
Last year, Jiro Sakaue of the Southern Marine Laboratory of Palau came across the unique eel while diving in a deep fringing-reef cave near Palau. He brought the find to his colleagues to investigate.
Sakaue and his team began by analyzing the physical features of eight of the eel specimens. The researchers compared the creatures' anatomic characteristics to those of modern eels—which includes over 800 species grouped into 19 families—and to ancient eel fossils.
The new species, the scientists found, showed traits present only in the fossils of the earliest eels, dating back to 100 million years ago. The major similarities between the new species and the fossils include a disproportionally large head, certain fused skull bones, a particular jawbone, and a relatively small number of vertebrae. The creature also has features that are unique in the eel world, such as gill rakers (structures involved in feeding and gill maintenance) resembling those in bony fishes.
By analyzing the eels’ mitochondrial DNA, the researchers learned that the eels date back to 200 million years ago, 100 million years earlier than the oldest eel fossil that scientists have found so far.
Because of the eels’ antique characteristics, the researchers decided to name the species Protoanguilla palau, where protoanguilla means “first eel.” P. palau even got its own family, Protoanguillidae.
What’s the Context:
Although the eel doesn’t have a fossil record to go by, the research team considers P. palau a living fossil, a name given to species that remain relatively unchanged after surviving for millions of years. Some other living fossils include the coelacanth, the horseshoe crab, and the nautilus.
P. palau may be ancient, but its cavern home is only 10,000 to 110,000 years old, according to study co-author Hitoshi Ida. "I think that what we see is a remnant of their habitat," Ida told Discovery News. The researchers also think that the eel may live in other remote habitats.
] Image courtesy of Jiro Sakaue