Comparative Analysis of the Umami Taste Receptor Gene in Mustelidae.

Pseudogenization of the umami taste receptor gene has been reported more commonly in aquatic than terrestrial mammals. We hypothesized that the more species are adapted to the aquatic environment, the less important a role the umami taste detection plays. To test this hypothesis, we focused on the Mustelidae family because their habitat and feeding ecology are highly diverse. We found pseudogenizing mutations in exon 1 of Eurasian otter and exon 6 of African clawless otter, both of which forage underwater. Our analysis of the ratio of nonsynonymous to synonymous nucleotide substitution rates suggested that purifying selection pressures on are weaker in the lineages with non-functional than the lineages retaining functional . Our analysis also suggested that relaxed selection pressures on in Mustelidae species adapted to the aquatic environment, although we cannot exclude the possibility that they are restricted to Lutrinae irrespective of their feeding habitat. Overall, the results of the present study support the idea that differences in selection pressures on reflect differences in feeding behaviors.