PARIS: A Universityof Michigan-led study of penguin genetics has concluded that the flightless aquatic birds lost three of the five basic vertebrate tastes — sweet, bitter and the savoury, meaty taste known as umami —more than 20 million years ago and never regained them. Because penguins are fish eaters, the loss of the umami taste is especially perplexing, said study leader Jianzhi Zhang, a professor.
Zhang suspects the sensory changes are tied to ancient climatecooling events in Antarctica, where penguins originated. His leading hypothesis is that the genes were lost after cold Antarctic temperatures interfered with taste perception. A paper regarding the study appears in the journal Current Biology. Vertebrates typically possess five basic tastes: sweet, sour, salty, bitter and umami. Compared with mammals, birds are thought to be poor tasters, due in part to the observations that they have fewer taste buds on their tongues and lack teeth for chewing food.
Previous studies showed that the sweet taste receptor gene is absent from the genomes of all birds examined to date. They found penguins lack functional genes for the receptors of sweet, umami and bitter tastes. Penguins originated in Antarctica after their separation from tubenose seabirds around 60 million years ago, and the penguin groups separated from one another about 23 million years ago. The taste loss likely occurred during that 37-million-year span, which included periods of dramatic climate cooling in Antarctica.
