Embargoed for release: 16-Feb-2015 12:00 ET (16-Feb2015 17:00 GMT)
Genetic evidence shows penguins have 'bad
taste'
Cell Press
Penguins apparently can't enjoy or even detect the savory taste of the fish they eat or the
sweet taste of fruit. A new analysis of the genetic evidence reported in the Cell Press journal
Current Biology on February 16 suggests that the flightless, waddling birds have lost three of
the five basic tastes over evolutionary time. For them, it appears, food comes in only two
flavors: salty and sour.
Many other birds, such as chickens and finches, can't taste sweet things either. But they do
have receptors for detecting bitter and umami (or meaty) flavors.
"Penguins eat fish, so you would guess that they need the umami receptor genes, but for some
reason they don't have them," says Jianzhi "George" Zhang of the University of Michigan.
"These findings are surprising and puzzling, and we do not have a good explanation for them.
But we have a few ideas."
It was Zhang's colleagues in China who led him to this discovery after they realized that they
couldn't find some of the taste genes in their newly sequenced genomes of Adelie and
emperor penguins. Zhang took a closer look at the penguin DNA to find that all penguin
species lack functional genes for the receptors of sweet, umami, and bitter tastes.
The researchers suggest that genes encoding those taste receptors may have been lost in
penguins not because they weren't useful, but rather because of the extremely cold
environments in which penguins live. (While some penguins have since moved to warmer
climes, all penguins trace their roots to Antarctica.)
Unlike receptors for sour and salty, the taste receptors required for detecting sweet, umami,
and bitter tastes are temperature sensitive. They don't work when they get really cold anyway.
In other words, even if penguins had those taste receptors, the receptors wouldn't be much use
to many of them.
Penguin tongues are also unusual in other ways, the researchers note. Anatomical studies
have suggested that some penguins lack taste buds--the primary location for taste receptors-altogether. Their tongues are instead covered with stiff, sharp papillae covered by a thick,
horny layer. It seems that penguin tongues are used not so much to taste food, but rather to
catch and hold onto it.
Penguins also have a habit of swallowing their food whole, which might leave them less
concerned about what their food actually tastes like. Or could it be the other way around?
"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," Zhang says.
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Current Biology, Zhao et al., "Molecular evidence for the loss of three basic tastes in
penguins"
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both by publishing important findings of general interest and through highly accessible front
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Author Contact:
Jianzhi "George" Zhang
Marshall W. Nirenberg Collegiate Professor
Department of Ecology and Evolutionary Biology
University of Michigan
Phone (office): 734-763-0527
Email: jianzhi@umich.edu
Home page: http://www.umich.edu/~zhanglab
Media Contact:
Jim Erickson
Senior Public Relations Representative
Phone (office): 734-647-1842
Email: ericksn@umich.edu