NEWS
NORMAN, OKLA. – A recently published study in Geology presents a new outlook on how relatives of sea stars change over millions of years and the factors that influence the rate of those changes. University of Oklahoma Mewbourne College of Earth and Energy faculty and Sam Noble Oklahoma Museum of Natural History curators Selina Cole and David Wright, along with Jeffrey Thompson of the University of Southhampton, led the study conducting experiments on the regenerative properties of brittle stars to see whether ocean chemistry in the ancient past may have impacted this rate of regeneration. From there, they aimed to identify whether there was any correlation between short-term regeneration and long-term term evolutionary diversification over millions of years.
“Paleobiology is a cross-disciplinary subject that involves synthesizing information about ‘big ideas’ from both the geophysical and biological sciences,” said David Wright, Ph.D., assistant curator of invertebrate paleontology at the Sam Noble Museum and assistant professor in the OU School of Geosciences. “Similarly, studying the effects of seawater chemistry on ocean life was interesting to us because we thought it could provide a simple link between plate tectonics and other geophysical changes in Earth's history with the large-scale evolutionary patterns in the history of life.”
Starfish and their relatives are known for their incredible ability to regrow lost or damaged limbs, but researchers believed the minerals and nutrients available in ancient oceans could significantly impact the rate of this regeneration.
“We wanted to see how brittle stars might have lived and how fast they could grow in a ‘calcite sea,’ such as during the Cretaceous when dinosaurs like Tyrannosaurs rex were living on land and marine reptiles like mosasaurs were major predators in the oceans.” Wright said, “But Cretaceous-aged seawater isn’t something you can just buy at an aquarium store, so we had to learn how to be geochemists and create our own seawater treatments from scratch. We spent a lot of time in the lab making seawater.”
The experimental results suggest a strong relationship between short-term regeneration and available minerals in seawater. It might be common sense to assume that increasing rates of regeneration would have a corresponding impact on how quickly these animals changed and evolved over time, but the results were unexpected.
“Our experiments involving modern brittle stars show a strong relationship between echinoderm regeneration and seawater chemistry.” Wright says, “On its own, these results would imply we should find a similarly strong relationship between patterns of evolutionary diversification in echinoderms and the chemical composition of seawater through time. Surprisingly, when we look to the fossil record to compare what actually happened, we see no evidence that changes in seawater chemistry had any impact on their long-term diversification.” He continues, “At the moment, we have more questions than answers. What we can say is our results provide an example where long-term evolutionary outcomes are not predicted by simply extrapolating results from short-term, experimental observations.”
The impact of the study extends beyond sea stars or any single group of animals. While many soft-bodied animals leave little or no trace for us to study in the fossil record, echinoderms, which include starfish, brittle stars, sea urchins, crinoids, and sea cucumbers, are extremely well represented as fossils. As a result, they give us an extremely broad and thorough look at their development and history, which provides scientists with invaluable clues about how other forms of life might evolve.
“There are five major groups of echinoderms today, but fossils indicate there have been around 30 or so major groups in their evolutionary history.” Wright said, “Understanding why so many of these lineages went extinct while others are alive today helps us understand more than just what happened to groups of echinoderms millions of years ago. It also helps us understand more general features of evolution and extinction, which is relevant for predicting how species may respond to environmental change and other threats to the biosphere in the future.”
About the Sam Noble Oklahoma Museum of Natural History
The Sam Noble Museum is the officially designated natural history museum for the state of Oklahoma and is located on the University of Oklahoma campus at 2401 Chautauqua Ave., in Norman.
About the University of Oklahoma
Founded in 1890, the University of Oklahoma is a public research university located in Norman, Oklahoma. As the state’s flagship university, OU serves the educational, cultural, economic and health care needs of the state, region and nation. OU was named the state’s highest-ranking university in U.S. News & World Report’s most recent Best Colleges list. For more information about the university, visit ou.edu.
About the Mewbourne College of Earth and Energy
The Mewbourne College of Earth and Energy at the University of Oklahoma educates scientists and engineers and creates knowledge of Earth’s past and present to navigate a future that meets societal needs for both energy and a livable environment. From engineering ways to converting abandoned oil wells to geothermal producers, to probing Earth’s past climate, to designing ways to sequester carbon, MCEE faculty are striving to create a better and more sustainable world.
