Penguins ignorant of the sea's finest flavors

Penguins would probably eat anything. It just so happens that fish are readily available in the cold, oxygen-rich waters of the Arctic. As a new study reveals, the palettes of penguins are comparatively crippled -- the Frank Bruni of the animal kingdom they are not. They aren't even the Guy Fieri.
As far as omega threes are concerned, penguins and their diet rich in fatty fish are ahead of the curve. But as far as the taste and flavor profiles of the food items penguins shovel down their pipes, the flightless aquatic birds are mostly in the dark. As researchers at the University of Michigan recently confirmed, penguins lack three of the five main taste buds and are unable to detect sweet, bitter and the elusive meat-like taste called umami.
"Penguins eat fish, so you would guess that they need the umami receptor genes, but for some reason they don't have them," Jianzhi 'George' Zhang, a professor in ecology and evolutionary biology at Michigan, explained 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."
The birds, researchers found in analyzing the palette-specific portion of the penguin's genome, lost their ability to discern sweet, bitter and umami flavors some 20 million years ago. All five species of penguin share the same limited palate, researchers found.
But doing away with the taste buds may be an economical rather than a philistine rejection of haute Antarctic cuisine. Previous studies show that the protein Trpm5 -- essential for the transduction of sweet, umami and bitter flavor signals from the tongue to the brain -- doesn't function well at cold temperatures.
"This give us a hint, perhaps, that this loss of taste genes has something to do with the inability of this protein to work at lower temperatures," explained Zhang.
Even if the portion of genome responsible for the three flavor receptors weren't genetic dead weight, and Trpm5 could function in the cold, penguins slurp their fish down whole, mostly bypassing any chance of their tongues doing much flavor analysis.
"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 said.
The new study was published this week in the journal Current Biology.