Dr. Todd Robeck of SeaWorld Discusses Using Epigenetic Clocks to Determine True Age of Marine Animals

Scientists have been able to implement epigenetic clocks previously only used in human studies to research how aging impacts the DNA of several species of marine animals. These clocks are extremely effective for determining chronological age in humans, and now, in several types of mammalian species.

For a little insight into how the process works, marine scientists take the known age of ocean-based animals in controlled environments, like public zoos and aquariums, and compare that data to wild populations to calculate an age distribution. Marine researchers can make accurate predictions about the age of marine animals in the wild by examining blood and tissue samples and comparing them to the controlled group, and by using the epigenetic clock.

Dr. Todd Robeck is a member of the research team at SeaWorld. He also serves as the Director of the Species Preservation Laboratory at SeaWorld and is the Vice President of Conservation Research in Animal Health.

Grey Stafford, the host of the podcast Zoo Logic, recently invited Dr. Robeck to the show to discuss marine research related to determining the chronological age of ocean life. Dr. Robeck uses the epigenetic clock method when determining the age of marine organisms.

Dr. Robeck Outlines the Use of Epigenetic Clocks with Odontocetes

The science of epigenetic clocks has existed for use with humans for the past few decades. As Dr. Robeck explains on the podcast, it is only recently that he and other marine organism researchers began using this method with mammals.

Dr. Robeck is currently working on a research project that looks at DNA markers in marine animals to come up with a close estimate of their age. Epigenetic clocks are one of his primary research tools when studying odontocetes, which are cetaceans with teeth found in the oceans.

What is Epigenetics?

Epigenetics refers to the modification of human or animal DNA at any point after birth or during fetal development. The DNA of every living organism establishes itself at conception and modifies over time through external factors in the environment. Dr. Robeck gave the example of metabolism producing antioxidants that can harm DNA. This is especially common as humans and animals age.

Changes that occur on DNA strands typically occur at random. As methylation occurs, it converts an entire methyl group of DNAS into acetone. When this process takes place (and where it happens within a gene) can either produce proteins or turn off the genetic function to accomplish this. Gene expression can change into an RNA messenger that helps to regulate body functions.

The DNA of humans and animals becomes damaged from the aging process alone, but other factors can accelerate the aging process. Environmental pollutants and stress are the leading outside contributors to the degradation of DNA.

How Epigenetics Applies to Dr. Robeck’s Research

Dr. Robeck explained to Grey Stafford how he uses a process of elimination to identify DNA changes and then further determines which changes relate to aging. The goal is to isolate age-related DNA changes to arrive at a close estimate of a marine animal’s chronological age.

Dr. Robeck also utilized data from a researcher named Steve Horvath at the University of California-Los Angeles (UCLA). Horvath has developed technology that can identify approximately 38,000 cytosine locations on DNA, along with their state of methylation. Steve Horvath works with a team of genetic researchers who have made these discoveries possible.

Dr. Robeck worked with Steve Horvath and his team to create the epigenetic clock for use with odontocetes. He then used the tool to study nine species of odontocetes. He discovered that combining their methylation patterns and comparing data from captive odontocetes with a known age enabled him to accurately estimate the chronological age of wild marine animals.

Dr. Robeck Discusses Accelerated Aging in Mammals

SeaWorld’s Dr. Robeck stresses that DNA methylation is a normal part of the aging process for humans and animals. The challenge comes in selecting which changes are relevant to detecting the chronological age of marine mammals and which ones are not. He and his team have isolated several environmental factors that change DNA and used the epigenetic clock to predict an accurate age between 90 and 95 percent of the time.

Accelerated aging is the same as a mammal’s biological age. Dr. Robeck and his team are trying to determine whether the biological age and the chronological age of the marine animals in their study match. When the two figures are close to the same, it means that the animal has an easier time handling oxidative stress and exposure to environmental toxins.

The Two Fundamental Purposes of Dr. Robeck’s Research

As Dr. Robeck explains, the epigenetic clock makes it possible to determine biological age with a margin of error of five years in either direction. Blood and tissue samples from marine animals are the most efficient ways to perform this dating.

Determining chronological age is especially useful when working with female marine animals, as it tells researchers which animals are still capable of reproducing. Knowing the age of marine animals is also useful for males and non-reproductive aged females to determine their capacity to be a functioning part of the population. For example, do they have the stamina to assist with foraging or teaching the adolescents of their species?

The second primary purpose of Dr. Robeck’s research is to use dating capabilities to determine the overall health of a marine species. By using the epigenetic clock, researchers can predict with greater accuracy whether a species will become extinct and when that is likely to happen. On the other hand, populations of odontocetes with many young mammals bode well for the ongoing survival of the species.

After determining the approximate chronological age of a marine animal, the SeaWorld veterinarian states that the next step is to figure out whether accelerated aging is occurring. If so, he feels it is important to find out which environmental triggers are causing the animals to act and appear older than their known age.

Dr. Robeck decides whether accelerated aging is occurring by comparing DNA methylation between marine animals in the wild and those in captivity. He states that marine researchers expect individual DNA differences between animals and place greater emphasis on large variations between populations.

If one group of marine animals shows signs of normal aging and the other shows signs of accelerated aging, the researchers know that outside influences are impacting the latter. However, they do not always know what those outside influences are without additional research.

An Alternative Method for Marine Researchers to Measure Chronological Age

Unfortunately, Dr. Robeck cannot always determine an approximate chronological age for his study subjects, even with access to advanced tools. When this happens, the team records the current date and sets a reminder to check the animal again in five or ten years. Animals that age normally should only appear and act five to ten years older at that time.

Marine animals that show accelerated aging during the follow-up study indicate to the research team that they face some type of outside stress. The stress could be anything, from lack of food to ocean pollution, and the researchers’ main priority is to correct whatever problem is causing an increase in oxidative stress for marine animals. Studying the degradation of DNA and methylation also makes it possible for marine researchers to predict the cause and date of death for each animal.

Dr. Robeck’s Shift from Treating Individual Marine Animals to Populations

Dr. Todd Robeck began his career with SeaWorld in 1993. He initially worked as a veterinarian for individual animals in various capacities. As time went on, SeaWorld management decided to draw on the skills that Dr. Robeck perfected and practiced while earning his Ph.D. in reproductive physiology. He also holds an undergraduate degree in marine biology.

Dr. Robeck states that he has always had an interest in marine organisms at more of a population level. He also describes his interest in ocean health and how the health of marine animals ties into it. According to the SeaWorld veterinarian, cetaceans are a top-level trophic species. Their overall health is instrumental in maintaining the health of the ocean, which is why he works so hard to protect them.

The Effects of Dr. Robeck’s Research Study So Far

As of midyear 2021, Dr. Robeck and his team have assigned an approximate age to 400 marine animals from nine species. Examples of some of the marine animals they have studied include:

  • Beluga whales
  • Dolphins
  • Killer whales
  • Pilot whales
  • Toothed whales

Many of these marine animals were juveniles when Dr. Robeck and his SeaWorld colleagues first studied them years ago. Approximately 80 percent of the animals in this study were born in captivity, making it easier for Dr. Robeck to know their age from the beginning of their life.

In some of his closing comments to Grey Stafford, Dr. Robeck describes how he feels fortunate for this opportunity as a marine biologist, veterinarian, and reproductive physiologist. He has spent his whole adult life working in zoo settings and studying animals in the wild. For Dr. Todd Robeck of SeaWorld, the opportunity to work with UCLA on this study has been a true honor. Learn more about what SeaWorld parks, including the San Diego location, have to offer.