There is no such thing as a food connoisseur penguin, suggests new research that found penguins can't taste savory or sweet flavors.
For the flightless, waddling birds, foods come in just two flavors -- salty and sour -- according to the new study, which is published in the latest issue of the journal Current Biology.
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"Penguins eat fish, so you would guess that they need the umami receptor genes, but for some reason they don't have them," co-author Jianzhi "George" Zhang of the University of Michigan said in a press release. "These findings are surprising and puzzling, and we do not have a good explanation for them. But we have a few ideas."
Zhang and colleagues made the determination after sequencing the genomes for Adelie and emperor penguins. The researchers were surprised that they couldn't find some basic taste genes, so they took a closer look at penguin DNA.
This led the scientists to conclude that all penguin species lack functional genes for the receptors of sweet, umami and bitter tastes.
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You might think that's obvious, because penguins aren't exactly noshing on candy or umami-laden soy sauce. But the reason for the loss likely has more to do with temperature than what the penguins are eating. The clues for this are the missing taste receptors themselves.
Those for sweet, umami and bitter flavors are temperature sensitive. They don't work well, if at all, if the individual is eating cold food in a cold environment. That's one reason why people can't taste the flavors in ice cream very well after a while. The cold dampens their taste buds, as well as ability to smell, a bit.
Penguins or their ancestors probably had all of the usual taste receptors at one point, but lost them when they moved to cold environments. Some penguins have since moved to warmer areas, but because all penguins trace their roots to Antarctica, penguins the world over are still hardwired, taste-wise, for eating in a colder habitat.
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The researchers further suspect that penguin tongues, with their sharp papillae appendages, are built more for grabbing onto slippery food than tasting edibles.
Before you feel too sorry for penguins, remember that they swallow their food whole. It's not as though they're going to swish fishmeal in their mouths a/la a wine aficionado in hopes of detecting different flavors.
Zhang said, "Their behavior of swallowing food whole, and their tongue structure and function, suggest that penguins need no taste perception, although it is unclear whether these traits are a cause or a consequence of their major taste loss."
Photo: Emperor penguins. Credit: John Landis/NSF, Wikimedia Commons