Salty, sweet, sour, bitter, and umami (savory) are the five primary tastes that we experience on a daily basis. Not only does it make eating an enjoyable experience, but taste also protects animals from consuming toxic substances.
A study published recently in the journal Genome Biology and Evolution reveals that cetaceans (whales and dolphins) may only be able to taste one of those five: salt. Mutations in a cetacean ancestor caused a massive loss of taste receptors, making cetaceans the first group of mammals to have lost the majority of this key sensory system. Researchers studied the genomes of 15 species, spanning the two major lineages of cetaceans: baleen whales (like minkes) and toothed whales (including sperm whales and dolphins).They found that the taste genes weren’t entirely gone, but “irreparably damaged” by mutations. In all of the studied species, the same mutations were seen for sweet, bitter, umami, and sour taste receptors. The only kind left intact were salty taste receptors.It’s not as disappointing a loss for whales as it would be for us because flavors are typically release by chewing, and cetaceans tend to swallow their food whole. However, the loss of bitter taste is particularly interesting because it could be dangerous.“The loss of bitter taste is a complete surprise, because natural toxins typically taste bitter,” said zoologist Huabin Zhao of Wuhan University in China who led the study. The fact that the salty receptors remained intact suggest that it plays an important role, such as maintaining sodium levels or blood pressure. Cetaceans are clearly not too adversely affected by the loss, but the question remains: how could they afford to lose four of the five primary tastes?
© 2014 by Marine Science Today; Feng, Ping, et al. "Massive losses of taste receptor genes in toothed and baleen whales." Genome biology and evolution 6.6 (2014): 1254-1265.