Penguins have lost their ability to taste their primary food source-fish. It is not clear how but the above fact has been proved scientifically.
Nature has endowed most vertebrates with five common taste receptors- sweet, salty, sour, bitter and umani. According to new genetic research, penguins have lost three of the five tastes sensations-sweet, bitter and umani which is the savory taste associated with meat. Penguins live exclusively on a fish diet and this is a startling according to the leader of the study Jianzhi “George” Zhang, a professor in the University of Michigan Department of Ecology and Evolutionary Biology.
George said in a statement, “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.”
George postulates that the taste receptors could have been lost during cooling periods in Antarctica where penguins originated about 60 million years ago. Zhang further added temperatures, plummeting into a brutal cold, interfered with taste perception.
Scientists in the last 15 years have learned a great deal about the molecular basis of taste. Accordingly scientists have been able to understand taste abilities from the genetic data of a number of species.
Most birds have poor taste abilities as compared to mammals. Birds do not have teeth for chewing, lesser taste buds overall and sweet taste receptors are also missing in most birds examined to date.
George and his two Chinese colleagues were prompted to study on penguins after an email from a Chinese Genomic Institute. Researchers at the institute had sequenced genomes from Emperor and Adelie Penguins. They found some of the taste genes absent and wanted help to understand if there is a problem with incomplete sequencing or whether the genes were actually missing.
Zhang and his team pored over the data as well as tissue samples from king, rockhopper and chinstrap penguins and eight closely related, non-penguin, species. The researchers also examined the genes for 14 more non-penguin bird species.
Researchers found that all the five penguin species lacked genes for sweet, bitter and unami tastes. In Emperor and Adelie genomes, the bitter and unami receptor genes have been transformed into ‘pseudogenes’. All the other birds contain unami and bitter genes though they lack the sweet genes. Pseudogenes lack the ability to encode proteins.