New occurrences of the bone-eating worm Osedax from Late Cretaceous marine reptiles and implications for its biogeography and diversification
By: Sarah Jamison-Todd, Philip D. Mannion, Adrian G. Glover and Paul Upchurch
Summarized by: Yasamin Taqwai is a biology major student at Binghamton University. She transferred this semester as a junior, after graduating with associates from Suny Broome University. Her lifelong dream and goal have been to be a doctor, especially an OBGYN. She hopes to attend Langone medical school after getting her bachelors. When she is not busy with school, she takes turns volunteering for health services and practicing self-care. She loves family time and baking as her therapy and peaceful time.
What data were used? Osedax are worms known for eating the bones of dead marine animals, such as whales or reptiles. They do not eat the whole bone, but by burrowing into it, they can break down the organic material, like the collagen and fat inside. The worms have a root-like structure that helps them penetrate the bone and release enzymes that dissolve the organic parts and absorb nutrients. This eating process creates holes and tunnels in the bone which makes up the fossil record of these worms (these are called trace fossils). The Osedax trace fossils used in this study were found on different marine reptiles from the Late Cretaceous Period, around 100 to 66 million years ago. There were 13 collections of these reptile fossils taken from in the United Kingdom, mainland Europe, and the United States. In these fossils, the researchers specifically looked for degradation or burrow structures that showed an Osedax worm had been present on them. The researchers also looked at CT scans of 20 specimens of Osedax with unique patterns. These patterns refer to the holes and tunnels created as the worms fed on the bones of the extremely well-preserved fossils of marine reptiles, such as plesiosaurs and mosasaurs.
What was the hypothesis being tested? Scientists wanted to research how Osedax worms have evolved over time: specifically, how their diversification into different species has been shaped by environmental factors and geographic differences. The researchers hypothesized that there was a greater species variation in Osedax than what previous studies had recognized. The researchers also hypothesized that Osedax fossils were found across a broader geographical range than previously thought, suggesting they spread to more areas than earlier studies had recognized. This was important for understanding not just the worms themselves but also for examining how they interacted and contributed to the health of marine ecosystems, such as how ecosystem maintained its balance during the Cretaceous.
Methods: Scientists examined fossil reptiles by analyzing the physical characteristics left by Osedax worms. They specifically studied the size and shape of boreholes and tunnels made by the worms as they fed on the bones (Fig. 1). These differences in borehole size provided information on variations in the worms’ eating habits. These size variations also potentially reflected different species of Osedax, as each species might create boreholes of distinct dimensions or patterns. The fossils with Osedax pattern on them were scanned using different CT scanners to get a detailed examination of the pattern. After visualizing characteristics of the trace fossils, the researchers looked at the geographical locations of where the fossils were discovered. They compared the variations they found across different geographical locations. They were looking for trends, whether certain species of Osedax worms were more common in specific regions or the size of boreholes varied based on location. These trends could help identify differences in their feeding behaviors, showing how environmental factors may have influenced their range and adaptation.
Results: The results of the study supported the hypothesis that Osedax worms had a greater species diversity and a broader geographic range than previously known. After analyzing different patterns left by Osedax the researchers were able to identify five different hole morphotypes, which suggests the presence of different species of Osedax worms that likely fed on marine reptiles. One significant finding came from a fossil connected with the Cenomanian Stage of the Late Cretaceous (~100–93 million years ago), which showed three different morphotypes within a single tooth, indicating the worms may have coexisted on the same organism. The study also found that Osedax had a greater geographic distribution, expanding their previously known range from the eastern side of the northern Atlantic Ocean to include the western side as well. They also believe that Osedax speciation occurred earlier than the timeline they had thought. This is based on the discovery of high diversity in fossils from older marine reptiles compared to the previously studied fossils of whale bones. The presence of multiple Osedax species in these earlier fossils suggests that the worms had diversified significantly before the Cenozoic Era (the past 65 million years), a time they are commonly associated with. Finally, the study also discusses a bias in Osedax speciation. Since these worms need well-oxygenated environments to thrive, fossils from low oxygen or deep ocean habitats may not show Osedax feeding traces. This means that the record of Osedax trace might be incomplete, further influencing our perception of their diversity and distribution over time and need to be researched further.
Why is this study important? This study helps us understand the interactions between Osedax worms and marine reptiles during the Late Cretaceous. It shows how these bone-eating worms did not function as parasites, but as decomposers, feeding on the bones of dead marine animals, such as plesiosaurs and mosasaurs. By burrowing and breaking down collagen and fat, it left distinct trace fossils which are valuable for identifying Osedax trace and knowing their ecological role. It also shows how Osedax can affect the preservation of fossils. Their feeding activity could mean that some marine reptile fossils collected today are incomplete as it could have impacted how well these organisms were preserved. These potential gaps in the fossil record could change our interpretation of past ecosystems. Additionally, the researchers believe that Osedax worms diversified earlier than previously thought, pushing back the timeline for their evolution. These findings mean we might not have a complete picture of the ecosystem and can reevaluate the timeline more precisely based on the new information and see the ecological significance of Osedax worms.
Broader Implications beyond this study: By studying Osedax worms, we can learn more about how marine ecosystems function and how different species interact. For example, when Osedax worms decomposes the bones of dead marine animals, they release nutrients for other organisms to consume and benefit from. This shows the interconnectedness of marine life and the importance of decomposers in maintaining a balanced ecosystem. Although Osedax worms and the marine reptiles they fed on are extinct, other organisms today, such as marine fungi, play a similar role. These organisms can be important for maintaining the balance of marine ecosystems and ensuring that nutrients from dead organisms are returned to the food web to support the thrive of other marine life. If these similar decomposers are threatened by pollution or climate change the nutrient cycle could be disrupted. Understanding the role of Osedax could help form strategies to protect or restore these organisms. Through Osedax, scientists can better understand how these processes worked in the past and apply that knowledge to modern ecosystems.
Citation: Jamison-Todd, S., Mannion, P. D., Glover, A. G., & Upchurch, P. (2024). New occurrences of the bone-eating worm Osedax from Late Cretaceous marine reptiles and implications for its biogeography and diversification. Proceedings of the Royal Society B Biological Sciences, 291(2020). https://doi.org/10.1098/rspb.2023.2830