5. DISCUSSION
This study has confirmed the specific expression of 22 copies of ORs in
the bottom region of the nasal chamber in common minke whales. The ORs
were predominantly expressed in the posterior portion of the nasal
chamber, facing towards the olfactory bulb, with higher expression
levels observed in the frontoturbinal region (R-006) and moderately in
ethmoturbinal II (R-001). It has been previously reported that these
nasal turbinals in typical mammals are covered with the olfactory
epithelium (Van Valkenburgh et al., 2014a). Furthermore, the expression
level of OMP was found to be highest in sample R-006, indicating that
the posterior portion of the frontoturbinal region can be identified as
olfactory region. Although the OMP expression in R-001 (0.966) did not
meet the criteria of 1.014, it was higher than expression levels
observed in R-046, R-008, R-214 and R-215 which showed no expression of
OMP. Moreover, the expression of ORs in R-001 was distinctly higher than
in R-046, R-008, R-214 and R-215, although lower than R-006 (Table 3).
These findings lead us to hypothesize that the sampled region R-001,
specifically the posterior medial surface of ethmoturbinal II (Fig. 1b),
encompasses both respiratory and olfactory areas. It is commonly
reported that respiratory and olfactory mucosae are distributed in a
mosaic-like pattern, and this distribution may hold for cetaceans as
well.
In this study, we conducted microscopic examination of the ethmoturbinal
II (H-001), frontoturbinal (H-009), and anterior region of the nasal
chamber (H-046). These samples were assessed based on the histological
criteria proposed by Farnkopf et al. (2022), and were likely identified
as olfactory mucosa. However, it was the proximal region of the
frontoturbinal (R-006) that strongly suggested being the olfactory
epithelium based on RNA-seq data. Notably, the same region (H-009)
exhibited a rich abundance of peripheral nerves, indicating its high
sensitivity. On the other hand, within H-046, which was obtained from a
more anterior region of the nasal cavity, dense clusters of vessels with
thick walls were observed (Fig. 5). This region may serve as a
respiratory area where the vascular epithelium plays a role in
thermoregulation.
Although the expressed ORs did not form a distinct cluster in the
phylogenetic tree (Fig. 4), it should be noted that the present study
does not exclude the possibility of a concealed cluster consisting of
ORs expressed in unexplored regions. This is because the distribution of
ORs, which mediate odoriferous stimuli to the olfactory bulb, is not
uniform across the olfactory epithelium (Ressler et al., 1993; Vassar et
al., 1993; Marchand et al., 2004). Furthermore, the distribution pattern
of the olfactory mucosa within the nasal chamber varies among lineages;
(Smith et al., 2011; Ruf, 2014; Smith et al., 2014)(Smith et al., 2011;
Ruf, 2014; Smith et al., 2014; Ito et al., 2021). It is plausible that
common minke whales possess additional ORs that contribute to their
olfactory modality, and identifying such receptors would enhance our
understanding of the molecular mechanisms underlying cetacean olfaction.
To comprehend the expression pattern of ORs, a thorough anatomical
examination of the cetacean nasal chamber is indispensable. Our
observations unveiled the presence of additional nasal turbinals
positioned laterally to ethmoturbinals I and II (Fig. 2b, FT and IT),
which have been scarcely documented in cetaceans. However, due to the
dearth of comprehensive anatomical data encompassing the entire nasal
chamber, precise determination of the exact locations from which H-046
and R-046 were obtained remained elusive. Nasal turbinals can be broadly
categorized into olfactory and respiratory turbinals, both of which play
a pivotal role in unraveling the aquatic adaptation of these creatures
(Van Valkenburgh et al., 2011; Van Valkenburgh et al., 2014a; Martinez
et al., 2020). In the nasal chamber of common minke whales, the anterior
segment from which H-046 and R-046 were harvested is inferred to
represent the respiratory region. It is conceivable that baleen whales
also possess respiratory turbinals, and investigating this structure is
warranted in future studies. Although the present study primarily
focused on the posterior region adjacent to the cribriform plate, it is
crucial to obtain a comprehensive understanding of the entire
architecture of this intricate labyrinth (Van Valkenburgh et al.,
2014b).
Fundamental anatomical data can function as an Atlas during dissection
process. As highlighted by Farnkopf et al. (2022), the extraction of the
nasal chamber from the cranial bones of large whales presents a
formidable challenge due to its remarkable dimensions, thickness, and
robust structure. The identification of the nasal turbinals from
sectional images can prove challenging, as their appearance exhibits
variations with slight deviations in cutting angles. Moreover, the
intricate nature of this structure impedes the efficient penetration of
fixation solutions into the tissues. To surmount these sampling
difficulties, the comprehensive description of the entire nasal chamber
using CT imaging becomes imperative. Subsequently, the determination of
olfactory epithelium distribution emerges as the next crucial step. The
locations of the olfactory epithelium might be predicted based on the
surface coloration of the nasal mucosae. While the majority of the nasal
mucosa in common minke whales displayed a pale pink hue, R-006, which
exhibited distinct olfactory characteristics, was obtained from an
epithelium displaying a yellowish appearance. A previous study
tentatively proposed the possibility of yellow pigmentation in the
olfactory epithelium of bowhead whales (Farnkopf et al., 2022).
The entirety of the expressed ORs identified in this study exclusively
belong to class-2 (Fig.4). While there remained significant room for
exploration, the probability of class-1 OR expression in common minke
whales is presumed to be minimal even when thoroughly screening the
entire lining mucosa of the nasal chamber. This presumption is rooted in
the observed morphology, which unveiled the absence of the dorsal domain
of the olfactory bulb in common minke whales. Class-1 olfactory
receptors typically transmit input to the dorsal domain of the olfactory
bulb. Consequently, it is anticipated that class-1 ORs would not be
expressed in the nasal mucosa of an animal lacking this specific region
of the olfactory bulb. It has been documented that bowhead whales have
also lost the dorsal domain of the olfactory bulb (Thewissen et al.,
2011; Kishida et al., 2015b), and the investigated common minke whales
exhibit a dorsoventrally flattened olfactory bulb, akin to that of
bowhead whales.
This study strongly suggests that the class-1 ORs do not partake in
olfactory reception in baleen whales. In mice, class-1 ORs receive
stimuli that trigger avoidance behaviors and project them into the
dorsal domain of the olfactory bulb (Kobayakawa et al., 2007). Hence,
our findings imply the loss of the typical avoidance response to
specific odorants, such as predators or putrefying substances, in
whales.
Considering that Sirenians, another lineage of fully aquatic mammals,
still retain their olfactory organ and possess a large repertoire of ORs
(Barboza and Larkin, 2020; Han et al., 2022; Christmas et al., 2023),
the diminished olfactory ability of baleen whales cannot be sorely
attributed to their aquatic lifestyle, which restricts continuous
respiration. One possible explanation for this lies in the necessity for
discerning ingested foods. Anatomically, the esophagus of cetaceans is
separated from the airway (Tyack and Miller, 2002), preventing them from
detecting smells emanating from the oral cavity. Genomic research has
revealed a degeneration of sense of taste, the other form of
chemoreception, in cetaceans (Feng et al., 2014; Zhu et al., 2014;
Kishida et al., 2015a; Policalpo et al., 2023). Furthermore, there is no
anatomical description of taste buds in the tongues of baleen whales
(Sonntag, 1922; Ogawa and Shida, 1950; Tarpley, 1985). Consequently, it
follows that baleen whales do not rely on chemosensory modalities to
evaluate food within their mouths, which may have contributed to the
reduction of their olfactory capabilities.
Our histological and genomic investigations suggest that residual
class-2 ORs are responsible for olfaction in baleen whales.
Specifically, the present study indicates that baleen whales are able to
receive preferred odors, such as those associated with prey and
potential mating partners. This research establishes a foundational link
between the anatomy and genome of baleen whales, and further
investigations hold the potential to illuminate the natural social and
behavioral biology of these animals, thereby aiding in their
conservation.
Acknowledgements
We are grateful to late Hideyoshi Yoshida for helping a lot during
sample collection. We thank Saeko Kumagai and Hiroto Murase for
collecting the skin samples; Kai Ito for identifying nasal turbinals;
Masahide Hasobe for staining; Takashi Sakamoto for preparing surgical
instruments; Andrew Shedlock for improving the manuscript; and our Lab
members. This study was financially supported by the Moritani
Scholarship Foundation, Grant for Basic Science Research Projects from
The Sumitomo Foundation (grant no. 180641), KAKENHI (Grant-in-Aid for
JSPS fellows, grant no. 23KJ0956). Computations were partially performed
on the NIG supercomputer at ROIS National Institute of Genetics.
DATA AVAILABILITY
STATEMENT
All sequence reads were deposited in the DDBJ Sequence Read Archive
under BioProject accession no. PRJDB16252.
REFERENCES
Barboza MLB, Larkin IV. 2020. Gross and Microscopic Anatomy of the Nasal
Cavity, Including Olfactory Epithelium, of the Florida Manatee
(Trichechus manatus latirostris ). Aquatic Mammals 46:274-284.
Berta A, Ekdale EG, Cranford TW. 2014. Review of the cetacean nose:
form, function, and evolution. The Anatomical Record 297:2205-2215.
Bird DJ, Murphy WJ, Fox-Rosales L, Hamid I, Eagle RA, Van Valkenburgh B.
2018. Olfaction written in bone: cribriform plate size parallels
olfactory receptor gene repertoires in Mammalia. Proceedings of the
Royal Society B: Biological Sciences 285:20180100.
Bolger AM, Lohse M, Usadel B. 2014. Trimmomatic: a flexible trimmer for
Illumina sequence data. Bioinformatics 30:2114-2120.
Bouchard B, Barnagaud J-Y, Poupard M, Glotin H, Gauffier P, Torres Ortiz
S, Lisney TJ, Campagna S, Rasmussen M, Célérier A. 2019. Behavioural
responses of humpback whales to food-related chemical stimuli. PloS one
14:e0212515.
Bouchard B, Barnagaud J-Y, Verborgh P, Gauffier P, Campagna S, Célérier
A. 2022. A field study of chemical senses in bottlenose dolphins and
pilot whales. The Anatomical Record 305:668-679.
Buck L, Axel R. 1991. A novel multigene family may encode odorant
receptors: a molecular basis for odor recognition. Cell 65:175-187.
Buiakova O, Baker H, Scott J, Farbman A, Kream R, Grillo M, Franzen L,
Richman M, Davis L, Abbondanzo S. 1996. Olfactory marker protein (OMP)
gene deletion causes altered physiological activity of olfactory sensory
neurons. Proceedings of the National Academy of Sciences 93:9858-9863.
Camacho C, Coulouris G, Avagyan V, Ma N, Papadopoulos J, Bealer K,
Madden T. 2009. BLAST+: architecture and applications. BMC
Bioinformatics 10:421.
Chen Z, Zhao H, Fu N, Chen L. 2018. The diversified function and
potential therapy of ectopic olfactory receptors in non-olfactory
tissues. Journal of Cellular Physiology 233:2104-2115.
Christmas MJ, Kaplow IM, Genereux DP, Dong MX, Hughes GM, Li X, Sullivan
PF, Hindle AG, Andrews G, Armstrong JC, Bianchi M, Breit AM, Diekhans M,
Fanter C, Foley NM, Goodman DB, Goodman L, Keough KC, Kirilenko B,
Kowalczyk A, Lawless C, Lind AL, Meadows JRS, Moreira LR, Redlich RW,
Ryan L, Swofford R, Valenzuela A, Wagner F, Wallerman O, Brown AR, Damas
J, Fan K, Gatesy J, Grimshaw J, Johnson J, Kozyrev SV, Lawler AJ,
Marinescu VD, Morrill KM, Osmanski A, Paulat NS, Phan BN, Reilly SK,
Schäffer DE, Steiner C, Supple MA, Wilder AP, Wirthlin ME, Xue JR,
Consortium§ Z, Birren BW, Gazal S, Hubley RM, Koepfli K-P, Marques-Bonet
T, Meyer WK, Nweeia M, Sabeti PC, Shapiro B, Smit AFA, Springer MS,
Teeling EC, Weng Z, Hiller M, Levesque DL, Lewin HA, Murphy WJ, Navarro
A, Paten B, Pollard KS, Ray DA, Ruf I, Ryder OA, Pfenning AR,
Lindblad-Toh K, Karlsson EK, Bredemeyer KR, Clawson H, Di Palma F,
Eizirik E, Forsberg-Nilsson K, Garcia CJ, Halsey MK, Harris AJ, Hickey
G, Juan D, Korstian JM, Lehmann T, Lind A, Mackay-Smith A, Mason VC,
Moore JE, Moreno-Santillan DD, Muntané G, Ortmann S, Pratt HE, Rosen JR,
Serres A, Springer M, Srinivasan C, Storer JM, Sullivan KAM, Sundström
E, Talbot J-E, Teeling E, Turner-Maier J, Wang C, Wang J, Zhang X. 2023.
Evolutionary constraint and innovation across hundreds of placental
mammals. Science 380:eabn3943.
Chu KC. 1988. Dive times and ventilation patterns of singing humpback
whales (Megaptera novaeangliae ). Canadian Journal of Zoology
66:1322-1327.
Clementz MT, Goswami A, Gingerich PD, Koch PL. 2006. Isotopic records
from early whales and sea cows: contrasting patterns of ecological
transition. Journal of Vertebrate Paleontology 26:355-370.
Corona R, Lévy F. 2015. Chemical olfactory signals and parenthood in
mammals. Hormones and Behavior 68:77-90.
Cranford TW, Amundin M, Norris KS. 1996. Functional morphology and
homology in the odontocete nasal complex: Implications for sound
generation. Journal of Morphology 228:223-285.
Danciger E, Mettling C, Vidal M, Morris R, Margolis F. 1989. Olfactory
marker protein gene: its structure and olfactory neuron-specific
expression in transgenic mice. Proceedings of the National Academy of
Sciences 86:8565-8569.
Doty RL. 1986. Odor-guided behavior in mammals. Experientia 42:257-271.
Farnkopf IC, George JC, Kishida T, Hillmann DJ, Suydam RS, Thewissen
JGM. 2022. Olfactory epithelium and ontogeny of the nasal chambers in
the bowhead whale (Balaena mysticetus ). The Anatomical Record
305:643-667.
Feng P, Zheng J, Rossiter SJ, Wang D, Zhao H. 2014. Massive Losses of
Taste Receptor Genes in Toothed and Baleen Whales. Genome Biology and
Evolution 6:1254-1265.
Fukuda N, Yomogida K, Okabe M, Touhara K. 2004. Functional
characterization of a mouse testicular olfactory receptor and its role
in chemosensing and in regulation of sperm motility. Journal of cell
science 117:5835-5845.
Gatesy J, Geisler JH, Chang J, Buell C, Berta A, Meredith RW, Springer
MS, McGowen MR. 2013. A phylogenetic blueprint for a modern whale.
Molecular phylogenetics and evolution 66:479-506.
Go Y, Niimura Y. 2008. Similar numbers but different repertoires of
olfactory receptor genes in humans and chimpanzees. Molecular Biology
and Evolution 25:1897-1907.
Godfrey SJ, Geisler J, Fitzgerald EMG. 2013. On the olfactory anatomy in
an archaic whale (Protocetidae, Cetacea) and the minke whale
Balaenoptera acutorostrata (Balaenopteridae, Cetacea). The Anatomical
Record 296:257-272.
Han W, Wu Y, Zeng L, Zhao S. 2022. Building the Chordata Olfactory
Receptor Database using more than 400,000 receptors annotated by
Genome2OR. Science China Life Sciences 65:2539-2551.
Hedley SL, Bannister JL, Dunlop RA. 2011. Abundance estimates of
Southern Hemisphere breeding stock ‘D’humpback whales from aerial and
land-based surveys off Shark Bay, Western Australia 2008. The Journal of
Cetacean Research and Management 3:209-221.
Hirose A, Kishida T, Nakamura G. 2018. Nasal mucosa resembling an
olfactory system in the common minke whale (Balaenoptera
acutorostrata ). Cetacean Population Studies 1:25-28.
Hirose A, Kodera R, Uekusa Y, Katsumata H, Katsumata E, Nakamura G, Kato
H. 2022. Comparative anatomy of and around the posterior nasofrontal sac
of a beluga whale. Marine Mammal Science 38:1272-1285.
Ichishima H. 2016. The ethmoid and presphenoid of cetaceans. Journal of
morphology 277:1661-1674.
Ito K, Kodeara R, Koyasu K, Martinez Q, Koyabu D. 2022. The development
of nasal turbinal morphology of moles and shrews. Vertebrate Zoology
72:857-881.
Ito K, Tu VT, Eiting TP, Nojiri T, Koyabu D. 2021. On the embryonic
development of the nasal turbinals and their homology in bats. Frontiers
in Cell and Developmental Biology 9:613545.
Katoh K, Rozewicki J, Yamada KD. 2019. MAFFT online service: multiple
sequence alignment, interactive sequence choice and visualization.
Briefings in Bioinformatics 20:1160-1166.
Kim D, Langmead B, Salzberg SL. 2015. HISAT: a fast spliced aligner with
low memory requirements. Nature Methods 12:357-360.
Kishida T. 2021. Olfaction of aquatic amniotes. Cell and Tissue Research
383:353-365.
Kishida T, Go Y, Tatsumoto S, Tatsumi K, Kuraku S, Toda M. 2019. Loss of
olfaction in sea snakes provides new perspectives on the aquatic
adaptation of amniotes. Proceedings of the Royal Society B 286:20191828.
Kishida T, Thewissen JGM. 2012. Evolutionary changes of the importance
of olfaction in cetaceans based on the olfactory marker proteingene. Gene 492:349-353.
Kishida T, Thewissen JGM, Hayakawa T, Imai H, Agata K. 2015a. Aquatic
adaptation and the evolution of smell and taste in whales. Zoological
Letters 1:9.
Kishida T, Thewissen JGM, Usip S, Suydam RS, George JC. 2015b.
Organization and distribution of glomeruli in the bowhead whale
olfactory bulb. Peerj 3:e897.
Klima M. 1999. Development of the Cetacean Nasal Skull. Advances in
anatomy, embryology and cell biology 149:1-143.
Kobayakawa K, Kobayakawa R, Matsumoto H, Oka Y, Imai T, Ikawa M, Okabe
M, Ikeda T, Itohara S, Kikusui T. 2007. Innate versus learned odour
processing in the mouse olfactory bulb. Nature 450:503-508.
Kozlov AM, Darriba D, Flouri T, Morel B, Stamatakis A. 2019. RAxML-NG: a
fast, scalable and user-friendly tool for maximum likelihood
phylogenetic inference. Bioinformatics 35:4453-4455.
Kuraku S, Zmasek CM, Nishimura O, Katoh K. 2013. aLeaves facilitates
on-demand exploration of metazoan gene family trees on MAFFT sequence
alignment server with enhanced interactivity. Nucleic Acids Research
41:W22-W28.
Maier W, Ruf I. 2014. Morphology of the Nasal Capsule of Primates—With
Special Reference to Daubentonia and Homo . The Anatomical
Record 297:1985-2006.
Malnic B, Hirono J, Sato T, Buck LB. 1999. Combinatorial receptor codes
for odors. Cell 96:713-723.
Marchand JE, Yang X, Chikaraishi D, Krieger J, Breer H, Kauer JS. 2004.
Olfactory receptor gene expression in tiger salamander olfactory
epithelium. Journal of Comparative Neurology 474:453-467.
Martinez Q, Clavel J, Esselstyn JA, Achmadi AS, Grohé C, Pirot N, Fabre
P-H. 2020. Convergent evolution of olfactory and thermoregulatory
capacities in small amphibious mammals. Proceedings of the National
Academy of Sciences 117:8958-8965.
Miller PJO, Roos MMH. 2018. Breathing. In: Würsig B, Thewissen JGM,
Kovacs KM., editor. Encyclopedia of Marine Mammals. San Diego, CA:
Academic Press. p 140-143.
Moran DT, Rowley JC, Jafek BW, Lovell MA. 1982. The fine structure of
the olfactory mucosa in man. Journal of Neurocytology 11:721-746.
Nei M, Niimura Y, Nozawa M. 2008. The evolution of animal chemosensory
receptor gene repertoires: roles of chance and necessity. Nature Reviews
Genetics 9:951-963.
Neuhaus EM, Zhang W, Gelis L, Deng Y, Noldus J, Hatt H. 2009. Activation
of an olfactory receptor inhibits proliferation of prostate cancer
cells. Journal of Biological Chemistry 284:16218-16225.
Niimura Y. 2009a. Evolutionary dynamics of olfactory receptor genes in
chordates: interaction between environments and genomic contents. Human
Genomics 4:1-12.
Niimura Y. 2009b. On the origin and evolution of vertebrate olfactory
receptor genes: comparative genome analysis among 23 chordate species.
Genome Biol Evol 1:34-44.
Niimura Y, Matsui A, Touhara K. 2014. Extreme expansion of the olfactory
receptor gene repertoire in African elephants and evolutionary dynamics
of orthologous gene groups in 13 placental mammals. Genome Res
24:1485-1496.
Niimura Y, Nei M. 2003. Evolution of olfactory receptor genes in the
human genome. Proceedings of the National Academy of Sciences
100:12235-12240.
Niimura Y, Nei M. 2005. Evolutionary dynamics of olfactory receptor
genes in fishes and tetrapods. Proceedings of the National Academy of
Sciences 102:6039-6044.
Niimura Y, Nei M. 2007. Extensive gains and losses of olfactory receptor
genes in mammalian evolution. PloS one 2:e708.
Nikaido M, Matsuno F, Hamilton H, Brownell Jr RL, Cao Y, Ding W, Zuoyan
Z, Shedlock AM, Fordyce RE, Hasegawa M. 2001. Retroposon analysis of
major cetacean lineages: the monophyly of toothed whales and the
paraphyly of river dolphins. Proceedings of the National Academy of
Sciences 98:7384-7389.
Ogawa T, Shida T. 1950. On the sensory tubercles of lips and oral cavity
in the sei and fin whale. Sci Rep Whales Res Inst 3:1-16.
Parmentier M, Libert F, Schurmans S, Schiffmann S, Lefort A, Eggerickx
D, Ledent C, Mollereau C, Gérard C, Perret J. 1992. Expression of
members of the putative olfactory receptor gene family in mammalian germ
cells. Nature 355:453-455.
Pihlström H, Fortelius M, Hemilä S, Forsman R, Reuter T. 2005. Scaling
of mammalian ethmoid bones can predict olfactory organ size and
performance. Proceedings of the Royal Society B: Biological Sciences
272:957-962.
Policarpo M, Baldwin M, Casane D, Salzburger W. 2023 Diversity and
evolution of the vertebrate chemoreceptor gene repertoire, PREPRINT
(Version 1) available at Research Square
[https://doi.org/10.21203/rs.3.rs-2922188/v1]
Ressler KJ, Sullivan SL, Buck LB. 1993. A zonal organization of odorant
receptor gene expression in the olfactory epithelium. Cell 73:597-609.
Roberts A, Trapnell C, Donaghey J, Rinn JL, Pachter L. 2011. Improving
RNA-Seq expression estimates by correcting for fragment bias. Genome
Biology 12:R22.
Roe LJ, Thewissen JGM, Quade J, O’Neil JR, Bajpai S, Sahni A, Hussain
ST. 1998. Isotopic Approaches to Understanding the Terrestrial-to-Marine
Transition of the Earliest Cetaceans. In: Thewissen JGM, editor. The
Emergence of Whales: Evolutionary Patterns in the Origin of Cetacea.
Boston, MA: Springer US. p 399-422.
Rouquier S, Giorgi D. 2007. Olfactory receptor gene repertoires in
mammals. Mutation Research/Fundamental and Molecular Mechanisms of
Mutagenesis 616:95-102.
Ruf I. 2014. Comparative anatomy and systematic implications of the
turbinal skeleton in Lagomorpha (Mammalia). The Anatomical Record
297:2031-2046.
Saito H, Chi Q, Zhuang H, Matsunami H, Mainland JD. 2009. Odor coding by
a Mammalian receptor repertoire. Science Signaling 2:ra9.
Smith TD, Eiting TP, Bonar CJ, Craven BA. 2014. Nasal morphometry in
marmosets: loss and redistribution of olfactory surface area. The
Anatomical Record 297:2093-2104.
Smith TD, Eiting TP, Rossie JB. 2011. Distribution of olfactory and
nonolfactory surface area in the nasal fossa of Microcebus
murinus : implications for microcomputed tomography and airflow studies.
The Anatomical Record 294:1217-1225.
Sonntag CF. 1922. The Comparative Anatomy of the Tongues of the
Mammalia.—VII. Cetaeea, Sirenia, and Ungulata. Proceedings of the
Zoological Society of London 92:639-657.
Spehr M, Gisselmann G, Poplawski A, Riffell JA, Wetzel CH, Zimmer RK,
Hatt H. 2003. Identification of a testicular odorant receptor mediating
human sperm chemotaxis. Science 299:2054-2058.
Springer M, Gatesy J. 2017. Inactivation of the olfactory marker protein
(OMP) gene in river dolphins and other odontocete cetaceans. Molecular
Phylogenetics and Evolution 109:375-387.
Tarpley RJ. 1985. Gross and microscopic anatomy of the tongue and
gastrointestinal tract of the bowhead whale (Balaena mysticetus ):
Texas A&M University. Doctoral thesis.
Thewissen J, George J, Rosa C, Kishida T. 2011. Olfaction and brain size
in the bowhead whale (Balaena mysticetus). Marine Mammal Science
27:282-294.
Trapnell C, Williams BA, Pertea G, Mortazavi A, Kwan G, van Baren MJ,
Salzberg SL, Wold BJ, Pachter L. 2010. Transcript assembly and
quantification by RNA-Seq reveals unannotated transcripts and isoform
switching during cell differentiation. Nature Biotechnology 28:511-515.
Trifinopoulos J, Nguyen L-T, von Haeseler A, Minh BQ. 2016. W-IQ-TREE: a
fast online phylogenetic tool for maximum likelihood analysis. Nucleic
Acids Research 44:W232-W235.
Tyack PL, Miller EH. 2002. Vocal anatomy, acoustic communication and
echolocation. Marine Mammal Biology: an evolutionary approach:142-184.
Van Valkenburgh B, Curtis A, Samuels JX, Bird D, Fulkerson B,
Meachen‐Samuels J, Slater GJ. 2011. Aquatic adaptations in the nose of
carnivorans: evidence from the turbinates. Journal of Anatomy
218:298-310.
Van Valkenburgh B, Pang B, Bird D, Curtis A, Yee K, Wysocki C, Craven
BA. 2014a. Respiratory and olfactory turbinals in feliform and caniform
carnivorans: the influence of snout length. The Anatomical Record
297:2065-2079.
Van Valkenburgh B, Smith TD, Craven BA. 2014b. Tour of a labyrinth:
exploring the vertebrate nose. The Anatomical Record 297:1975-1984.
Vassar R, Ngai J, Axel R. 1993. Spatial segregation of odorant receptor
expression in the mammalian olfactory epithelium. Cell 74:309-318.
Yim H-S, Cho YS, Guang X, Kang SG, Jeong J-Y, Cha S-S, Oh H-M, Lee J-H,
Yang EC, Kwon KK, Kim YJ, Kim TW, Kim W, Jeon JH, Kim S-J, Choi DH, Jho
S, Kim H-M, Ko J, Kim H, Shin Y-A, Jung H-J, Zheng Y, Wang Z, Chen Y,
Chen M, Jiang A, Li E, Zhang S, Hou H, Kim TH, Yu L, Liu S, Ahn K,
Cooper J, Park S-G, Hong CP, Jin W, Kim H-S, Park C, Lee K, Chun S,
Morin PA, O’Brien SJ, Lee H, Kimura J, Moon DY, Manica A, Edwards J, Kim
BC, Kim S, Wang J, Bhak J, Lee HS, Lee J-H. 2014. Minke whale genome and
aquatic adaptation in cetaceans. Nat Genet 46:88-92.
Zhou Y, Shearwin-Whyatt L, Li J, Song Z, Hayakawa T, Stevens D, Fenelon
JC, Peel E, Cheng Y, Pajpach F, Bradley N, Suzuki H, Nikaido M, Damas J,
Daish T, Perry T, Zhu Z, Geng Y, Rhie A, Sims Y, Wood J, Haase B,
Mountcastle J, Fedrigo O, Li Q, Yang H, Wang J, Johnston SD, Phillippy
AM, Howe K, Jarvis ED, Ryder OA, Kaessmann H, Donnelly P, Korlach J,
Lewin HA, Graves J, Belov K, Renfree MB, Grutzner F, Zhou Q, Zhang G.
2021. Platypus and echidna genomes reveal mammalian biology and
evolution. Nature 592:pages 756–762.
Zhu K, Zhou X, Xu S, Sun D, Ren W, Zhou K, Yang G. 2014. The loss of
taste genes in cetaceans. BMC Evolutionary Biology 14:218.