A new genetic study has found that penguins have lost their three of the five basic vertebral tastes over 20 million years ago and they have never regained them.
According to the researchers, even though it is true that these flightless aquatic birds are fond of eating fish but they hardly enjoy them tasting as they have lost their taste buds of bitter, sweet and umami.
The scientists are of the belief that the penguins’ sensory changes could be associated with the ancient climate-cooling events in Antarctica.
Study leader author Jianzhi “George” Zhang, an ecology and evolutionary biology professor at the University of Michigan, said that the main hypothesis is that the taste receptor genes present in penguins were lost due to the cold temperatures in the Antarctic that interfered with their taste perception.
“Penguins eat fish, so you would guess that they need the umami receptor genes, but for some reason they don’t have them. These findings are surprising and puzzling, and we do not have a good explanation for them. But we have a few ideas,” Zhang said in a statement.
The research work was prompted by a prior studies conducted by the scientists at a Chinese genomics institute. The institutes’ researchers had carried sequencing of genomes from emperor and Adelie penguins, but couldn’t find some of the genes linked with taste. They approached Zhang for determining whether the absent genes were due to the evolutionary process.
The data and the tissue samples from chinstrap, rockhopper and king penguins were closely analysed by Zhang and his team. All the five species were found having no functional genes for the receptors of tastes like umami, sweet and bitter.
The study group also analysed several non-penguin birds such as finches, egrets, parrots, flycatchers, falcons, macaws, mallards and chickens and found that all of them contained the genes for both bitter and umami tastes, but they lacked sweet taste receptors.
The penguins got separated from tubenose seabirds nearly 60 million years ago, while the major groups of penguin separated from each other nearly 23 million years ago.
On the other hand, the taste lost may have occurred during 37 million years span that witnessed periods of significant climate cooling in Antarctica, Zhang said.
The scientists said that the penguins primarily use their tongues to catch and hold the slippery fish or their other prey. But the scientists are still unclear about which came first: the sensory changes or the anatomical adaptations.
“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 study’s findings were published on Monday in the journal Current Biology.