Osedax Zombie worm has eaten up many fossil bones, scientists say

The Zombie worm, known formally as the Osedax worm, has been eating the bones of large creatures in our oceans for millions of years. Scientists had incorrectly assumed that it evolved in conjunction with whales.

About 100 million years ago, Osedax worms fed on the bones and cartilage of giant marine reptiles. Unfortunately, it means they have destroyed many fossils.

Researchers from the Marine Institute and the School of Geography, Earth & Environmental Sciences, both at Plymouth University, England, explained in the journal Biology Letters that Zombie worms fed on the bones of prehistoric reptiles, including pleriosaurs and sea turtles.

Authors Dr. Silvia Danise and Nicholas Higgs explain how they discovered the hallmark traces of the Osedax worm on plesiosaur fossils at the University of Cambridge Museum’s collection.

Osedax worm

The Osedax worm lives on the bones of dead sea animals. (Image: mbari.org)

Dr. Higgs said the discovery was important for both its implications for fossil records as well as our understanding of the genesis of the species.

Osedax did not evolve alongside whales

Dr. Higgs explained:

“The exploration of the deep sea in the past decades has led to the discovery of hundreds of new species with unique adaptations to survive in extreme environments, giving rise to important questions on their origin and evolution through geological time.”

“The unusual adaptations and striking beauty of Osedax worms encapsulate the alien nature of deep-sea life in public imagination. And our discovery shows that these bone-eating worms did not co-evolve with whales, but that they also devoured the skeletons of large marine reptiles that dominated oceans in the age of the dinosaurs.”

“Osedax, therefore, prevented many skeletons from becoming fossilised, which might hamper our knowledge of these extinct leviathans.”

A creature with no digestive system or mouth

The human finger-length Osedax worm, which thrives across all our oceans in depths of up to 4,000 metres, has no mouth or digestive system as an adult. It belongs to the Siboglinidae family of worms.

It penetrates bone using root-like tendrils which absorb bone collagen and fats (lipids), which are converted into energy by bacteria within it.

They are commonly found feeding on the bones of whales, an observation that prompted many scientists to believe erroneously that they co-evolved 45 million years ago, branching out from other related worms that used chemosynthesis to obtain food.

However, this latest study showed that the supposed co-evolution did not occur. The researchers studied fossil fragments taken from a plesiosaur unearthed in Cambridge and a sea turtle found in Burham in Kent.

They scanned the specimens a computed tomography scanner, a 3-dimensional X-ray machine, at the Natural History Museum, where they were able to create a computer model of the bones.

They found the tell-tale bore holes and cavities consistent with Osedax worms’ burrowing technique.

Dr Danise said:

“The increasing evidence for Osedax throughout the oceans past and present, combined with their propensity to rapidly consume a wide range of vertebrate skeletons, suggests that Osedax may have had a significant negative effect on the preservation of marine vertebrate skeletons in the fossil record.”

“By destroying vertebrate skeletons before they could be buried, Osedax may be responsible for the loss of data on marine vertebrate anatomy and carcass-fall communities on a global scale.”

“The true extent of this ‘Osedax effect’, previously hypothesized only for the Cenozoic, now needs to be assessed for Cretaceous marine vertebrates.”

Reference: Silvia Danise and Nicholas D. Higgs. “Bone-eating Osedax worms lived on Mesozoic marine reptile deadfalls.” Biology Letters. Published 15 April 2015. DOI: 10.1098/rsbl.2015.0072.

Video – Bone-eating worms