The olfactory receptor gene repertoires in secondary-adapted marine vertebrates: evidence for reduction of the functional proportions in cetaceans.
An olfactory receptor (OR) multigene family is responsible for the well-developed sense of smell possessed by terrestrial tetrapods. Mammalian OR genes had diverged greatly in the terrestrial environment after the fish-tetrapod split, indicating their importance to land habitation. In this study, we analysed OR genes of marine tetrapods (minke whale Balaenoptera acutorostrata, dwarf sperm whale Kogia sima, Dall's porpoise Phocoenoides dalli, Steller's sea lion Eumetopias jubatus and loggerhead sea turtle Caretta caretta) and revealed that the pseudogene proportions of OR gene repertoires in whales were significantly higher than those in their terrestrial relative cattle and also in sea lion and sea turtle. On the other hand, the pseudogene proportion of OR sequences in sea lion was not significantly higher compared with that in their terrestrial relative (dog). It indicates that secondary perfectly adapted marine vertebrates (cetaceans) have lost large amount of their OR genes, whereas secondary-semi-adapted marine vertebrates (sea lions and sea turtles) still have maintained their OR genes, reflecting the importance of terrestrial environment for these animals.
Kishida
Takushi
T
Department of Zoology, Kyoto University, Wakayama 649-2211, Japan. takushi@kishida.mbox.media.kyoto-u.ac.jp
Kubota
Shin
S
Shirayama
Yoshihisa
Y
Fukami
Hironobu
H
D000818:Animals; D001483:Base Sequence; D002417:Cattle / Q000235:genetics; D004285:Dogs / Q000235:genetics; D019143:Evolution, Molecular; D005260:Female; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D019576:Porpoises / Q000235:genetics*; D011544:Pseudogenes; D018035:Receptors, Odorant / Q000235:genetics*; D046070:Sea Lions / Q000235:genetics; D017422:Sequence Analysis, DNA; D014426:Turtles / Q000235:genetics; D014907:Whales / Q000235:genetics*
D018035:Receptors, Odorant