AsianScientist (May 30, 2014) – Genetic research on whales and dolphins show that they only possess functional taste receptors for salt, making them the first animal group to lack four out of five primary tastes. This research has been published in the journal Genome Biology and Evolution.
The five primary tastes are salty, sweet, sour, bitter and umami (savory). The sense of taste acts as a gate keeper, helping animals determine the suitability of food before ingestion. For example, the presence of bitter tastes might indicate that the food is contaminated with toxins, while umami indicates that the food is rich in proteins, causing the animal to avoid or accept the food correspondingly.
By sequencing taste receptors in 11 whale species covering both toothed and baleen whales, researchers from Wuhan University uncovered mutations in the sweet, sour, bitter and umami taste receptors which rendered them non-functional.
This finding that whales can only taste salt contradicts anecdotal evidence given by keepers of captive marine mammals who observe that the whales and dolphins in their care do show preferences, favoring mackerel over squid, for instance. However, these preferences could be due more to the texture of the food rather than their taste.
The authors suggest that the widespread loss of taste receptors in whales could be due to the dietary switch from plants to meat which has few sweet and bitter compounds or the fact that whales swallow their food without chewing, which prevents flavors from being released.
In contrast, the retention of the salt receptors indicates that salt-sensing is an essential function and may be required for the regulation of sodium ion fluxes, especially for sea-dwelling organisms.
The article can be found at: Feng et al. (2014) Massive losses of taste receptor genes in toothed and baleen whales.
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