Several posters at EB 2022 in Philadelphia this month were focused on understanding the remarkable physiology of diving seals. Although we may think of the image below when we picture seals, they really are quite the athletes in water.
Kaitlin Allen (a graduate student working in the laboratory of Dr. José Pablo Vázquez-Medina at the University of California Berkeley) presented her research on Northern elephant seals and how these animals experience dramatic changes in circulating oxygen concentrations while diving. That makes sense as it’s not like they wear a scuba tank or anything. This drop in oxygen is similar to what happens in humans experiencing a heart attack or stroke. But that is about where the similarities end as, unlike humans, seals do not develop vascular injuries resulting from the drop in oxygen when diving. Kaitlin’s team discovered that seals were able to protect their cells by activating antioxidants.
Amy Klink (a graduate student working with Dr. Allyson Hindle at the University of Nevada Las Vegas) presented her research that also examined how Weddell seals prevent ischemia-reperfusion injuries during dives. Similar to elephant seals, oxygen levels in Weddell seals drop when the animals are diving. To help protect vital organs, the animals divert blood away from the gut and peripheral tissues and send it instead to the brain, lungs and adrenal glands. When strokes and heart attacks happen in humans, blood flow similarly stops resulting in a decline in oxygen delivery to tissues. If blood flow resumes, it often causes reperfusion injuries marked by inflammation. Amy and her team are looking for evidence explaining how the seals prevent injuries and inflammation following a dive.
Lauren Cooley, a graduate student at Moss Landing Marine Laboratories working with a team of researchers from the University of California Santa Cruz, University of Nevada Las Vegas, Wildlife Technology Frontiers, Cornell University, Scripps Institution of Oceanography, and the National Marine Mammal Foundation examined how handling and transportation affect juvenile Northern elephant seals. To study this, they attached biologgers to the animals. Not surprising, they found the animals had higher levels of stress hormones when they were captured although stress levels returned to normal when the animals were returned to the sea.
Shawn Hannah, also a graduate student at Moss Landing Marine Laboratories used biologgers to measure other health parameters in Northern elephant seals. They found that the animal’s heart rate dropped to as low as 40-50 beats per minute during a dive, then increased again as the animals returned to the surface. This rise in heart rate may help the animals get rid of carbon dioxide and breath in oxygen faster – which is important in restoring levels.