A type of bone-gobbling worm that currently spends its days chomping through the skeletons of dead whales has actually been around for at least 100 million years, some 50 million years longer than originally believed, a new study has found. According to the research, these tiny, thread-like worms used to dine on prehistoric marine reptiles, such as plesiosaurs, and thus may have also left a dent in the fossil record. The study has been published in Biology Letters.
Nicknamed the “zombie worm,” Osedax is a bizarre, finger-length animal found in deep sea habitats worldwide. Although their name may mean “bone devourer,” these worms do not actually possess mouths and instead rely on acid to bore through skeletons. Osedax also don’t have stomachs, but they exploit beneficial bacteria which break down the fats and proteins present inside bones into nutrients that they can absorb and use as an energy source.
Since these worms are known for feeding on the bones of dead whales, or falls as they are called, it was assumed that these animals probably evolved at the same time, around 45 million years ago, when the ancestors of whales transitioned from land to sea. But some researchers proposed that they may have appeared much earlier than that, possibly feasting on ancient marine reptiles which roamed the seas during the time of the dinosaurs.
To find evidence for this idea, researchers from Plymouth University scrutinized the 100-million-year-old fossilized remains of a sea turtle and a plesiosaur’s flipper using a CT scanner, which created detailed computer models of the skeletons. The resulting 3D images revealed the presence of distinctive bore holes and cavities which were characteristic of the burrowing technique employed by Osedax today.
This suggests that Osedax did not in fact co-evolve with whales, but instead have been around at least since the early Cretaceous period. And when plesiosaurs became extinct during the Cretaceous-Tertiary mass extinction event, which wiped out the dinosaurs, these worms turned their attention to sea turtles and made a living off of them until whales came on the scene.
Alongside pushing back the date for the appearance of these unusual animals, these findings have implications for the fossil record as they may have prevented many skeletons from becoming fossilized.
“By destroying vertebrate skeletons before they could be buried,” explains lead researcher Silvia Danise, “Osedax may be responsible for the loss of data on marine vertebrate anatomy and carcass-fall communities on a global scale.”