The loss of taste genes in cetaceans

Abstract

BackgroundFive basic taste modalities, sour, sweet, bitter, salt and umami, can be distinguished by humans and are fundamental for physical and ecological adaptations in mammals. Molecular genetic studies of the receptor genes for these tastes have been conducted in terrestrial mammals; however, little is known about the evolution and adaptation of these genes in marine mammals.ResultsHere, all five basic taste modalities, sour, sweet, bitter, salt and umami, were investigated in cetaceans. The sequence characteristics and evolutionary analyses of taste receptor genes suggested that nearly all cetaceans may have lost all taste modalities except for that of salt.ConclusionsThis is the first study to comprehensively examine the five basic taste modalities in cetaceans with extensive taxa sampling. Our results suggest that cetaceans have lost four of the basic taste modalities including sour, sweet, umami, and most of the ability to sense bitter tastes. The integrity of the candidate salt taste receptor genes in all the cetaceans examined may be because of their function in Na+ reabsorption, which is key to osmoregulation and aquatic adaptation.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-014-0218-8) contains supplementary material, which is available to authorized users.

Molecular Footprints of Aquatic Adaptation Including Bone Mass Changes in Cetaceans

“…These findings are consistent with the recent studies proposing that cetaceans have a greatly reduced sense of smell, and cannot detect basic taste modalities (sweet, sour, and umami; the umami, also known as savory taste, described as meaty) except for salt, and have a reduced ability to sense bitter taste (Zhou et al. 2013; Zhu et al. 2014).…”

The life aquatic: advances in marine vertebrate genomics

“…Most taste receptors have been pseudogenized in cetaceans owing to multiple insertions and deletions that disrupt the open reading frame. The only exception is members of the epithelial sodium channel (ENaC) protein complex, which are thought to have a crucial role in the perception of salt taste and are therefore potentially important in sodium ion reabsorption and osmoregulation 20,21 . Similarly, the gene SMPX (small muscle protein, X-linked), which has a role in inner ear development 22 , was inferred to be evolving under positive selection along the branches to the cetaceans, pinnipeds and sirenians (from their respective terrestrial ancestors) 7 .…”

Epithelial sodium channel (ENaC) family: Phylogeny, structure–function, tissue distribution, and associated inherited diseases

“…Sequencing of the various cetacean genes for the receptors of the five tastes revealed that the receptor genes for four tastes are non-functional pseudogenes because of accumulation of mutations (Zhu et al, 2014). However, in contrast to these, the three ENaC subunits, α, β, and γ, that also serve as salt taste receptor have remained intact and functional.…”