Climate Change Was No Problem for the Big Fish
Research shows that sharks evolved from bottom dwellers to open ocean predators during a past global warming event, adapting with physical changes like elongated fins to become more efficient swimmers.
The sharks we know today as the open ocean’s top predators evolved from stubby bottom dwellers during a dramatic episode of global warming millions of years ago.
A massive outpouring of volcanic lava about 93 million years ago sent carbon dioxide levels soaring, creating a greenhouse climate that pushed ocean temperatures to their hottest. University of California, Riverside (UCR) researchers discovered that some sharks responded to the heat with elongated pectoral fins.
Scientific Discovery and Analysis
This discovery is documented in a paper published today (June 3) in the journal
Adaptations and Efficiency
Longer pectoral fins help make shark movements much more efficient. “Their fins are comparable to the wings of commercial airplanes, long and narrow, to minimize the amount of energy needed for movement,” Sternes said.
The researchers also saw that the open-water sharks got faster compared to bottom dwelling sharks. “Shark muscle is very sensitive to temperature,” said Tim Higham, professor in UCR’s Department of Evolution, Ecology, and Organismal Biology and paper co-author.
“The data helped us make a correlation between higher temperatures, tail movement, and swimming speeds,” Higham said.
Habitats and Evolutionary Pressures
Most living shark species are still bottom dwellers, occupying what scientists refer to as the benthic zone. These benthic sharks do not loom as large in popular culture as their fierce open-water relatives. Many of the bottom dwellers are slender, flatter, more medium-sized predators.
Only about 13% of modern sharks are fast-swimming open-water predators. The researchers believe that breathing may have become difficult for their ancient relatives. Oxygen levels near the bottom during the