title: Aquatic adaptation and the evolution of smell and taste in whales.
abstract: BACKGROUND
  While olfaction is one of the most important senses in most terrestrial mammals, it is absent in modern toothed whales (Odontoceti, Cetacea). Furthermore, behavioral evidence suggests that gustation is very limited. In contrast, their aquatic sistergroup, baleen whales (Mysticeti) retain small but functional olfactory organs, and nothing is known about their gustation. It is difficult to investigate mysticete chemosensory abilities because experiments in a controlled setting are impossible.
  
  
  RESULTS
  Here, we use the functional regionalization of the olfactory bulb (OB) to identify the loss of specific olfactory functions in mysticetes. We provide the whole-genome sequence of a mysticete and show that mysticetes lack the dorsal domain of the OB, an area known to induce innate avoidance behavior against odors of predators and spoiled foods. Genomic and fossil data suggest that mysticetes lost the dorsal domain of the OB before the Odontoceti-Mysticeti split. Furthermore, we found that all modern cetaceans are revealed to have lost the functional taste receptors.
  
  
  CONCLUSIONS
  These results strongly indicate that profound changes in the chemosensory capabilities had occurred in the cetacean lineage during the period when ancestral whales migrated from land to water.
authors.affiliation: Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo, Kyoto 606-8502 Japan ; Present affiliation: Wildlife Research Center, Kyoto University, 2-24 Tanaka Sekiden-cho, Sakyo, Kyoto 606-8203 Japan.
authors.forename: Takushi
authors.initials: T
authors.lastname: Kishida
authors.affiliation: Department of Anatomy and Neurobiology, Northeast Ohio Medical University, 4209 State Route 44, Rootstown, OH 44272 USA.
authors.forename: Jgm
authors.initials: J
authors.lastname: Thewissen
authors.affiliation: Primate Research Institute, Kyoto University, Kanrin, Inuyama, Aichi 484-8506 Japan ; Japan Society for the Promotion of Science, Kojimachi, Chiyoda, Tokyo 102-0083 Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Hayakawa
authors.affiliation: Primate Research Institute, Kyoto University, Kanrin, Inuyama, Aichi 484-8506 Japan.
authors.forename: Hiroo
authors.initials: H
authors.lastname: Imai
authors.affiliation: Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo, Kyoto 606-8502 Japan.
authors.forename: Kiyokazu
authors.initials: K
authors.lastname: Agata
keywords: Antarctic minke whale genome; Archaeoceti; Cetacea; Chemoreception; Olfactory bulb