WOULD you believe that red pandas are crazy for the artificial sweetener aspartame? In a study of how taste buds determine an animal's diet, Xia Li at Monell Chemical Senses Center in Philadelphia and colleagues let six mammals choose between plain water and water flavoured with natural and artificial sweeteners. Surprisingly, the red panda is very fond of aspartame (Journal of Heredity, in press).
Until now, it was thought that only certain primates could taste aspartame. Intrigued, the team searched for an evolutionary explanation. But when they compared the taste-bud genes of animals that could and could not taste aspartame, they found no significant difference. This suggests the ability to taste artificial sweeteners evolved randomly through chance mutations in the sweet receptor.
Joseph Brand, who supervised the research, thinks the type of taste receptor a species has could subtly influence the foods they choose to eat. For example, the giant panda - another mostly herbivorous mammal - eats bamboo shoots on different parts of the bamboo at different times of year. "The panda is presumably following the taste of something - maybe it's the taste of some specific sweetener in the leaves," says Brand.
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