Shark DNA could hold answers to how we age

A breakthrough in understanding how organisms age has emerged from a groundbreaking study involving zebra sharks, according to researchers at the University of Georgia. Scientists developed a novel method using epigenetic clocks, tools that track chemical modifications in DNA, to accurately estimate the age of sharks without harming them. This technique, which has previously been applied to other animals, represents the first successful application in sharks and could provide critical insights into marine biology and conservation efforts. The study focused on zebra sharks, which can live up to 30 years. Researchers collected blood samples from more than 50 zebra sharks housed in aquariums across the southeastern United States, including the Georgia Aquarium. By examining specific chemical tags in the sharks' DNA, scientists were able to estimate the animals' ages with remarkable precision, within two years of their actual chronological age. These findings were validated against existing age records maintained by the aquariums. Epigenetic clocks rely on the observation that as organisms age, certain chemical markers on their DNA undergo predictable changes. These changes reflect the gradual degradation of cellular structures, much like an old barn deteriorating over time. In humans, such changes manifest in visible signs like graying hair and wrinkled skin. For sharks, the same principle applies, allowing researchers to determine age based on these molecular shifts. The study also revealed that zebra sharks experience more pronounced changes in their DNA patterns during early development, particularly before reaching sexual maturity. Once mature, the rate of these changes slows down significantly, aligning with observations in mammalian species. This consistency across different vertebrate groups suggests that the mechanisms governing aging might be ancient and broadly conserved among animals with backbones. Traditional methods of determining a shark’s age involve lethal procedures, such as dissecting the animal to count growth rings on its vertebrae. Non-invasive techniques, while less common, often lack reliability. The new approach offers a promising alternative that preserves the lives of the studied animals while still yielding valuable data. Benjamin Parrott, corresponding author of the study and an associate professor at the University of Georgia’s Savannah River Ecology Laboratory and Odum School of Ecology, emphasized the importance of understanding age distribution in shark populations. “Age structure is one of the most important things conservation biologists can measure,” he stated. “If we could figure out how old wild sharks are, we could finally understand the age structure of their populations. That's incredibly important for conservation of marine populations.” The research team included Samantha Bock, a doctoral graduate from the Odum School, who noted the broader implications of their findings. “We knew that this process occurred in lots of mammals and some non-mammalian species, but we didn’t know how widespread this phenomenon was,” she explained. “This finding means we can potentially unlock key insights into the foundation of long life.” The results of the study were published in the journal Molecular Ecology. They demonstrated that the epigenetic clock method could be extended beyond controlled environments. When applied to a group of wild-caught sharks with unknown birth dates, the estimated ages were within three to four years of the actual ages, confirming the method’s potential applicability in natural settings. Researchers believe this technique will aid in assessing the health of shark populations by providing data on survival rates, reproductive cycles, and population dynamics. Such information is crucial for developing effective conservation strategies, especially given the increasing threats faced by marine ecosystems due to human activities. Further studies are planned to explore the application of this method in other shark species and marine animals. The ultimate goal is to refine the technique so it can offer even greater accuracy and utility in wildlife management and ecological research. The findings underscore the value of interdisciplinary approaches in advancing both biological science and environmental protection efforts.