Penguin hemoglobin evolved to meet oxygen demands of diving
Credit: Pixabay

More than 50 million years ago, the lovable tuxedoed birds began leaving their avian relatives at the shoreline by waddling to the water’s edge and taking a dive in the pursuit of seafood.

Webbed feet, flipper-like wings and unique feathers all helped penguins adapt to their underwater excursions. But new research from the University of Nebraska–Lincoln has shown that the evolution of diving is also in their blood, which optimized its capture and release of oxygen to ensure that penguins wouldn’t waste their breath while holding it.

Relative to land-dwelling birds, penguin blood is known to contain more hemoglobin: the protein that picks up oxygen from the lungs and transports it through the bloodstream before dropping it off at various tissues.

That abundance could partly explain the underwater proficiency of, say, the emperor penguin, which dives deeper than any bird and has been documented holding its breath for more than 30 minutes while preying on krill, fish and squid.

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Still, the particulars of their hemoglobin — and how much it actually evolved to help penguins become fish-gobbling torpedoes that spend up to half of their lives underwater — remained open questions. So Nebraska biologists Jay Storz and Anthony Signore, who often study the hemoglobin of birds that survive miles above sea level, decided to investigate the birds most adept at diving beneath it.

“There just wasn’t a lot of comparative work on blood-oxygen transport as it relates to diving physiology in penguins and their non-diving relatives,” said Signore, a postdoctoral researcher in Storz’s lab.

Source/Further Reading: University of Nebraska Lincoln