Why leaf-eating Asian monkeys do not have a sweet tooth

Genetic study shows that Javan lutung monkeys have a poor sense of taste

Date:  September 6, 2018

Source:  Springer

Asian colobine monkeys are unable to taste natural sugars, and in fact have a generally poor sense of taste. This is according to research led by Emiko Nishi of the Primate Research Institute of Kyoto University in Japan. Nishi and her colleagues found that the receptors on the tongues of colobine monkeys do not function in the same way as for fruit-eating monkeys, who are sensitive to sweet tastes. The study is published in the Springer Nature branded journal Primates, which is the official journal of the Japan Monkey Centre.

In general, mammals are able to taste sugary flavours thanks to the sweet taste receptor gene TAS1R2/TAS1R3 and related taste buds on the tongue. In a previous study, the same group of researchers showed that colobine monkeys do not pick up bitter tastes. Nishi and her colleagues conducted a series of laboratory and genetic tests to investigate these protein expressing cells reconstructed from leaf-eating Javan lutung monkeys (Trachypithecus auratus), which are part of the Colobinae subfamily of monkeys. These cells showed no reaction when natural sugars such as sucrose contained in sugarcane, fructose in fruit and maltose in fermented foods. Although the receptor genes are present, they seem not to function.

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