吸血蝙蝠丧失品尝苦味的能力

Vampire bats' strict blood diet has made them lose much of their ability to taste bitter flavours, a study has found.

一项研究发现，吸血蝙蝠绝对的血液饮食使它们失去了品尝苦味的能力。

Bitter taste acts as a natural defence against eating poisonous foods and was thought to be indispensable（不可缺少的） in animals.

Researchers say the bats' special diet and use of smell, echolocation and heat could have made taste less important.

Their work shows poor bitter taste is more widespread in animals than previously thought.

The findings are reported in the journal Proceedings of the Royal Society B.

Toxins typically taste bitter to animals but bottlenose dolphins and some whales have been shown to have reduced bitter taste, probably because they swallow their food whole, making taste unnecessary.

Vampire bats are the only mammals to feed solely on blood meaning they are unlikely to encounter toxic foods in the wild. The research team wanted to find out if that had left them with a lack of bitter taste.

Lead author, Professor Huabin Zhao, from Wuhan University, previously discovered that vampire bats had lost sweet and umami (savoury) tastes.

The researchers analysed the genomes of four bat species - representing two major subgroups of bats - and identified bitter taste receptor genes, which allow animals to taste bitter flavours.

As a result they predicted all bats should have bitter taste. 

They compared the sequences of nine taste receptor genes in all three species of vampire bats and 11 species of non-vampire bats.

They found vampire bats had a higher percentage of non-functioning bitter taste receptor genes (called pseudogenes) (47%) compared to non-vampire bats (4.3%). This demonstrated a greatly reduced bitter taste in vampire bats.