Scientists Develop Rapid DNA-Based Technique for Estimating Shark Lifespans

For one of the top apex predators in the ocean, age is more than just a number. Researchers at the University of Georgia are working to solve this mystery.

A new UGA study has found how to estimate shark ages by studying variations in individual animals’ DNA. These scientific age estimators, known as epigenetic clocks, rely on chemical changes called DNA methylation to detect wear and tear in an animal’s cells, offering a noninvasive, quick, and accurate way to estimate age.

Researchers have tested the predictive clock concept successfully in dozens of other animals, but this is the first time they have applied it to sharks.

According to the researchers, the technique could shed new light on the biological history of shark populations and the life cycles of other marine organisms with unknown aging data.

Age structure is one of the most important things conservation biologists can measure. 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.

Benjamin Parrott, Study Corresponding Author and Associate Professor, University of Georgia

Age Estimation Tool Suggests DNA Changes Slow in Adulthood

The researchers collected blood samples from over 50 zebra sharks in southeastern aquariums, including the Georgia Aquarium.

As organisms age, chemical tags in their DNA change, yet predictable patterns emerge over time.

Using only 10 distinct DNA tags, the researchers estimated the zebra sharks’ ages within two years of their chronological ages, without studying a full genetic sequence. They matched the estimates to aquarium age records to assess accuracy.

Given a zebra shark’s lifespan of up to 30 years, this is equivalent to mistaking someone for 26 when they are actually 27.

The epigenome is a lot like an old barn. It starts out well built, but over time things slowly fall apart. Our bodies age the same way. Our skin changes, our hair turns gray and DNA patterns drift too. The clocks pick up on that process.

Benjamin Parrott, Study Corresponding Author and Associate Professor, University of Georgia

The determined ages were within about three to four years of the initial measurements taken on the sharks when they were collected, even after testing a dozen more wild-caught sharks outside the aquarium with unknown birth dates.

The researchers also discovered that zebra sharks may mature more rapidly before reaching sexual maturity. Changes in DNA patterns were most noticeable in young, growing sharks before the rate of change declined during adulthood.

The slower changes in older animals align with what epigenetic clocks have shown in mammals. This study suggests that aging mechanisms have remained largely consistent throughout vertebrates (animals with backbones) for millions of years.

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. This finding means we can potentially unlock key insights into the foundation of long life.

Samantha Bock, Study Corresponding Author and Doctoral Graduate, Odum School of Ecology, University of Georgia

Understanding Aging can Enhance Marine Life Conservation

Traditional shark age determination methods involve killing the shark and counting growth rings on its spine. Researchers can also estimate age by observing sharks, but this is not always accurate. This novel technology might advance aging studies without endangering animals.

The researchers emphasized the importance of understanding aging patterns for species health. Age data can help determine survival rates, reproductive trends, and whether populations are expanding or diminishing. If a lot of older sharks are seen, it might indicate that their population is declining.

“Determining the age of an animal is often very difficult. But if we can use epigenetic patterns to measure the ages of sharks, we can use it as a tool to see these trends in vulnerable populations,” Bock added.

The clock can also help researchers understand how and why stress, disease, and environmental pressures accelerate molecular aging in sharks.

Following the success of the epigenetic clock with zebra sharks, this study might serve as a platform for further research on other endangered marine animals, supporting scientists in future population management decisions.

“Sharks play really important roles in maintaining balance in ecosystems. If you remove a predator from an ecosystem, things can get out of balance. The goal is to give conservation biologists another tool to make better management decisions,” Parrott concluded.