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aristarchus writes:

Original source is paywalled: The New York Times. Text extracted from https://www.sciencenews.org/article/fin-whale-eat-choke-baleen-oral-plug-muscle-fat.

Scientists have discovered a new anatomical structure that allows lunge-feeding whales to take in massive amounts of water without choking.

To capture prey, humpbacks, minkes and other whales use a tactic called lunge feeding. They accelerate — their mouths open to nearly 90 degrees — and engulf a volume of water large enough to fill their entire bodies. "It's crazy. Imagine putting an entire human inside your mouth," said Kelsey Gil, a zoologist studying whale physiology at the University of British Columbia.

As water floods into the whale's mouth, its throat pouch expands, leaving the whale looking like a bloated tadpole. After about a minute, the throat pouch deflates as most of the water leaves the whale's mouth, released back into the ocean. Small fish and krill are captured in the whale's baleen — plates of keratin that hang from the top of the whale's mouth resembling bristles on a toothbrush — and are swallowed into the whale's stomach.

Scientists didn't know how these whales avoided choking on prey-filled water and flooding their respiratory tracts during a lunge feeding event. Now Dr. Gil and colleagues have discovered a large, bulbous structure that they've termed the "oral plug" — a structure never before described in any other animal — that they think makes lunge feeding possible.

[...] By physically manipulating and dissecting the mass of muscle and tissue — the oral plug — the researchers determined that when the animal is at rest, the plug blocks off the whale's pharynx, a tube-shaped structure that leads to both the respiratory and digestive tracts, just like in other mammals including humans. When a whale lunges, the oral plug protects both tracts from being flooded by the water and the critters that the animal has taken in.

For the whale to ingest food, that oral plug needs to move. Again through manipulation and dissection, the researchers figured out that when the animal was ready to swallow its latest meal, the oral plug shifted upward to protect the upper respiratory tract, including the nasal cavities and blowhole. At the same time, the larynx — the structure in the pharynx that guards the entrance to the lungs — closes up and shifts downward, sealing off the lower respiratory tract. In other words, during swallowing, the pharynx only leads to the digestive tract and the upper and lower airways are protected.

Journal Reference:
Kelsey N. Gil, A. Wayne Vogl, Robert E. Shadwick. A 'trapdoor' made of muscle and fat helps fin whales eat without choking, Current Biology. Published online January 20, 2022. (DOI: https://doi.org/10.1016/j.cub.2021.12.040)

Original Submission