April 30, 2018 — Whales, dolphins and seals have evolved to hunt prey deep in the ocean, an environment that would otherwise prove deadly to animals that depend on breathing air to live. Until recently, scientists believed marine mammals’ known physical adaptations protected them from the effects of such punishing depths.

But scientists were baffled by computer models that showed that, even with the known adaptations, 50 percent of animals studied still should have experienced the bends. Researchers concluded there must be some else going on.

A new study by the Woods Hole Oceanographic Institution and the Oceanographic Foundation of the City of Arts and Sciences in Valencia, Spain, may provide an answer. The study, funded by the U.S. Navy, found that deep-diving marine mammals use a physical adaptation — the collapse of one portion of the lungs — to block the flow of nitrogen into the blood and prevents the animals from getting the bends, the crippling release of nitrogen gas that can occurs when surfacing from dives deeper than 130 feet.

“If you get the conditions right, you can get a nice exchange of oxygen and carbon dioxide but block the nitrogen,” said Michael Moore, a WHOI senior scientist who specializes in the analysis of marine mammal mortalities. Moore is a co-author of the study, which was published April 25 in the journal “Proceedings of the Royal Society B.”

The mammals have other physical adaptations that help them survive the depths when they exhaust available oxygen in their lungs, including a high amount of proteins in blood and muscle that bind oxygen and a higher ratio of red to white blood cells. Their ribs and lungs can collapse under pressure without breaking and their airways are hardened bunkers that remain partially open to power the signals they use to locate one another and their prey.

Read the full story at the Cape Cod Times