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A baby Weddell seal lounges on top of the sea ice
Photo Credit: Mike Lucibella
A baby Weddell seal lounges on top of the sea ice. Scientists hope to understand how the species is able to stay underwater for up to 90 minutes.

Seals Don’t Waste their Breath

If we can understand how they do it, it may one day advance medicine

The ubiquitous Weddell seals that live around McMurdo Station are the region’s undisputed diving champs.

Emmanuel Buys walks through a seal colony near the Hutton Cliffs
Photo Credit: Mike Lucibella
Emmanuel Buys walks through a seal colony near the Hutton Cliffs on Ross Island, looking for seals to study. NMFS permit No. 19439.

“One of the things that seals can do really well is dive and hold their breath for a really long time,” said Emmanuel Buys, a molecular biologist at Massachusetts General Hospital and principal investigator on the project. “They can actually function, and they can forage under the ice, and they can hunt for 90-plus minutes.”

That’s at least three times as long as any of the other air-breathing critters in the region. It’s an impressive feat, and how they’re able to stay under for so long is what Buys and his team have been investigating over the past two seasons in Antarctica. Their project is supported by the National Science Foundation, which manages the U.S. Antarctic Program.

Seals have a special trick that lets them conserve their oxygen as they stay down for long periods of time. They’ve evolved the ability to prioritize blood flow to their vital organs while restricting the flow to less essential ones.

Luis Huckstadt takes an ultrasound of a Weddell seal
Photo Credit: Mike Lucibella
Luis Huckstadt takes an ultrasound of a Weddell seal. NMFS permit No. 19439.

“There’s blood flowing through their brain and their hearts to keep them functioning, but their lungs, that they’re not using when they’re diving, are not receiving blood, their kidneys are not receiving blood,” Buys said.

By cutting down on the blood flow to the less-critical organs, they stretch out their limited supply of oxygen allowing them to stay under for much longer than they would be able to otherwise.

“We are interested in understanding the molecular biology and the genetics behind their ability to do that,” Buys said. “What allows them to function with low oxygen levels, also how they manage to redistribute blood to different organs in different ways?”

What’s particularly interesting to the researchers is how these adaptions in seals might relate to human physiology.

Emmanuel Buys and Rachel Berngartt take physical measurements of a Weddell seal
Photo Credit: Mike Lucibella
Emmanuel Buys and Rachel Berngartt take physical measurements of a Weddell seal. NMFS permit No. 19439.

“Mammals are amazingly similar in what we do,” said Allyson Hindle, researcher at Massachusetts General and co-principal investigator on the project. “We see so much tremendous variability, but what’s really amazing is that the starting points are very, very similar.”

Warren Zapol of the Massachusetts General Hospital and Dan Costa of the University of California, Santa Cruz, are also co-principal investigators on the project, but did not travel to Antarctica.

Researchers hope that a better understanding of how a seal’s body responds to oxygen deprivation could yield new insights into how the human body responds. Though still in its preliminary stages, there’s hope that this information could possibly lead to new medical treatments.

“We understand how that stuff kind of works in a human but [seals are] an animal that uses all of the same proteins, all of the same molecular biology that we have, they’re just using it differently,” Hindle said. “Finding a new way that nature is doing something is really important for finding new drugs.”

Emmanuel Buys records the Weddell Seal data he and his team collected
Photo Credit: Mike Lucibella
Emmanuel Buys records the Weddell Seal data he and his team collected. NMFS permit No. 19439.

The researchers believe that the key lies in how seals use the chemical nitric oxide. Most mammals naturally produce it in order to help regulate their blood pressure. When the muscles in blood vessels are exposed to nitric oxide they relax, causing the blood vessel to widen and allowing more blood to pass through. Synthetic nitric oxide has been a fixture of blood pressure medications for humans for years.

“[Seals] exhale almost no nitric oxide, suggesting that they may make less nitric oxide than we do,” Buys said. “That basically made us think that maybe these animals have a different nitric-oxide regulating system.”

Why Weddell seals’ nitric oxide usage is so unusual is what Buys and his team are trying to figure out. It could be any number of different steps in the system, from the production of the chemical compound to their muscles’ response to it.

Likely the answer lies in the genetic code that governs their biological processes. Buried somewhere in that code is sequence of DNA that regulates how much or how little nitric oxide is produced. The team hopes that by understanding how it’s different from other mammals, they can learn the secret of the seals ability to regulate their blood flow.

“We’re comparing the genome of a Weddell seal with dozens of other mammalian genomes,” Buys said. “Hopefully we’ll be able to identify variation in the genome that allows them to behave differently from any other terrestrial mammal.”

At their lab in the Crary Laboratory, Allyson Hindle tends to cell cultures collected from different seals
Photo Credit: Mike Lucibella
At their lab in the Crary Laboratory, Allyson Hindle tends to cell cultures collected from different seals. NMFS permit No. 19439.

To isolate exactly what’s happening, the team needed to analyze a variety of tissue samples from the seals.

“We’re particularly interested in blood vessels,” Hindle said.

Seals are a protected species under the Marine Mammal Protection Act, and as such the researchers can’t harm or injure them. So the team has had to get creative to find blood vessels they can collect without harming any live animals.

“One piece of an animal that we can collect is the placenta,” Buys said. “The animal has no use for it and we can dissect out blood vessels.”

A mother seal and her two babies lie on the sea ice
Photo Credit: Mike Lucibella
A mother seal and her two babies lie on the sea ice.

In addition, animals that have died of natural causes are also an excellent tissue source for the team. However they do have to be careful with these samples as relying on animals that have already perished could affect their results.

“Death is obviously not a pathology that’s good for you,” joked Kaitlin Allen, a graduate student at Colorado State University. “If we’re going to use samples from animals that are already deceased for reasons largely unknown to us, then there’s’ going to be a lot of variability.”

They also collected a limited amount of blood and tissue samples from healthy seals to ensure than what they’ve collected from deceased seals is an accurate representation of living seals. They can use these tissue samples to create stem cells, a kind of undifferentiated cell that can grow and become any kind in the body, including blood vessel cells.

Luis Huckstadt of the University of California, Santa Cruz and veterinarian Rachel Berngartt traveled with the team as well to help properly handle the animals. After five weeks of collecting, the team returned with about 22,000 different individual samples from about 60 sources.

Now back at their lab, the team, along with research assistants Annie Batten and Anne Schulberg, are working through what they’ve collected. They’re analyzing the proteins created by the cells’ RNA to see if they can isolate which genes regulate nitric oxide production.

In addition, the cell samples they collected have the opportunity to benefit numerous other researchers. By keeping the cell lines alive at their lab, researchers from around the world can have access to them for future projects.

“We’re establishing a lot of primary lines from as many different tissues as we can,” Hindle said. “With the addition of the stem cells, we in theory can make anything, so what science that would never have been possible, because you can’t collect those samples from live seals, might now at least be preliminarily possible for people in the U.S.”

NSF-funded research in this article: Emmanuel S Buys, Massachusetts General Hospital, Award No. 1443554. Research was conducted under National Marine Fisheries Services permit 19439 and Antarctic Conservation Act permit 2016-005.

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Curator: Michael Lucibella, Antarctic Support Contract | NSF Official: Peter West, Office of Polar Programs