Fat taste receptors and fatty milk in dolphins

Abstract There has been a long debate on whether cetaceans recognize external chemical compounds in water. Genetically, they lost some taste receptors due to their aquatic adaptations. In contrast, neuroanatomical and behavioral studies have suggested that young dolphins can perceive specific chemicals. In this study, we tested whether young dolphins could recognize fatty acids contained in their mother's milk. We performed mRNA sequencing of the tongue of a 1‐year‐old Indo‐Pacific bottlenose dolphin. Long‐chain fatty acid taste receptors were expressed in a V‐shaped row of the tongue, which is specific for young dolphins and has taste bud‐like structures. The lingual lipase is also expressed in the V‐shaped row, which may enhance the release of free fatty acids from triacylglycerols. Notably, the sour taste receptor was nonfunctionalized specifically in Indo‐Pacific bottlenose dolphins. We comprehensively qualified the fatty acids in the milk of captive common bottlenose dolphins. Seven saturated and 16 unsaturated long‐chain fatty acids were detected. Behavioral tests in captive common bottlenose dolphins showed that a juvenile can recognize the presence of milk in water. These results indicated that young dolphins may have functional fat taste receptors in their oral cavity that detect long‐chain fatty acids contained in their mother's milk.