Natures wonders: mitochondria in bird migrations (Introduction)

by David Turell , Tuesday, May 20, 2025, 21:52 (11 hours, 1 minutes ago) @ David Turell

They become supercharged:

https://www.quantamagazine.org/turbocharged-mitochondria-power-birds-epic-migratory-jou...

Weighing in at a single ounce, the white-crowned sparrow can fly 2,600 miles, from Mexico to Alaska, on its annual spring migration, sometimes traveling 300 miles in a single night. Arctic terns make even longer journeys of 10,000 miles and more from the Arctic Circle to Antarctica, while great snipes fly over food-poor deserts and seas, sometimes covering 4,200 miles in four days without stopping.

During migration season, many bird species become continent-spanning, high-endurance athletes. “They’re flapping their wings several times a second for up to eight hours at a time,” said Soren Coulson(opens a new tab), who studies migration physiology at the University of Memphis. For humans, an equivalent feat — say, running nonstop without food, water or rest for days at a time — would be unimaginable.

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Their studies show how small changes in the number, shape, efficiency and interconnectedness of mitochondria can have huge physiological consequences that contribute to birds’ long-duration, continent-spanning flights.

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These pioneering studies on mitochondrial performance and bird migration highlight the fact that a seasonal response to changing light levels, not physical preparation, triggers crucial subcellular changes, said Wendy Hood(opens a new tab), who studies physiological ecology at Auburn University in Alabama;

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The scientists found that birds experiencing the “migration” condition had more mitochondria, and that those mitochondria had a greater capacity to make energy(opens a new tab), compared to those in the “nonmigratory” birds. This suggested that during migration, the birds’ mitochondria are “turbocharged,” Coulson said. Then, after the journey is done, the mitochondrial landscape reverts to its usual state....

“All those turbocharged mitochondria become regular-charged mitochondria, [and] they get rid of the excess ones,” Coulson said. “That way, they can stop potentially wasting energy on traits that they no longer need for that time of the year.”

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Rhodes and her colleagues found that the flight muscles of migratory white-crowned sparrows had more numerous and more efficient mitochondria(opens a new tab), which used more oxygen, compared to the birds that didn’t migrate. While mitochondrial oxygen consumption was highest during migration, researchers observed that it ramped up before the birds began migrating.

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The findings suggest that changes in mitochondrial shape could play a direct role in giving birds their energy boost for long flights — a cellular adaptation that helps explain how such small birds can migrate such vast distances.

Turbocharged mitochondria come with a downside(opens a new tab), however. In the process of providing energy, mitochondria produce damaging molecules, known as reactive oxygen species, that can lead to health effects such as cardiovascular disease. If migratory birds build up more numerous and more powerful mitochondria, how do they deal with this tradeoff?

Diet may be one answer. Research by McWilliams and colleagues has shown that migratory birds are keen to eat fruits rich in antioxidants, which counteract these harmful molecules. Their experiments also demonstrated that the antioxidant vitamin E can enter mitochondria(opens a new tab) in the flight muscles of lab-raised birds, but only those trained to fly. This potentially counteracts the oxidative stress even at the level of the tiny organelle. Understanding more fundamentally how mitochondria provide birds with additional energy without overproducing reactive oxygen species is “a necessary next step” in this line of research, McWilliams said.

Comment: this raises questions; how do unguided birds learn to fly such long distances? How do mitochondria change in anticipation of the flights? Changing as a result of the flights is understandable. It all looks planned and designed to me.