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The olfactory anatomy and upper respiratory tracts of whales, dolphins, and their terrestrial relatives: Perspectives from morphology, histology, embryology, and evolutionary biology

Farnkopf, Ian Chun
http://orcid.org/0000-0002-7800-2335
http://rave.ohiolink.edu/etdc/view?acc_num=kent1653588212041775

Abstract Details

2022, PHD, Kent State University, College of Arts and Sciences / School of Biomedical Sciences.
Having transitioned from a terrestrial lifestyle to an aquatic one over roughly 50 million years, cetaceans (whales, dolphins, and porpoises) make for prime subjects of study of respiratory and olfactory anatomy. As obligately aquatic mammals, they are often considered to have reduced olfactory anatomy. Here, I provide evidence that baleen whales have retained this anatomy, and toothed whales lack olfactory anatomy. In reconstructing the upper respiratory tracts of prenatal dolphins from computed tomography, I document the anatomy of the air sacs, pterygoid sinus systems, and asymmetries thereof. Olfactory anatomy was absent. However, in bowhead whales (Balaena mysticetus), a species of baleen whale, nasal chambers and turbinates were visible in prenatal development. I describe and clarify the anatomy within their nasal chambers. Olfactory epithelium, identified histologically, covers the dorsalmost and caudalmost corner of the nasal chamber, including some of the ethmoturbinates. I identify olfactory epithelium using explicit criteria of mammalian olfactory epithelium. Immunohistochemistry revealed the presence of olfactory marker protein, which is only found in mature olfactory sensory neurons. Although it seems that these neurons are scarce in bowhead compared to typical terrestrial mammals, our results suggest that bowheads have a functional sense of smell, which they may use to find prey. The closest living relatives of cetaceans are artiodactyls, even-toed ungulates, such as sheep, camels, and giraffes. I used Cetartiodactyla, the clade that comprises artiodactyls and cetaceans, as the taxon to test the relationships found in Bird et al. (2018). They found that once body mass and phylogeny are accounted for, it is possible to use the surface area of the cribriform plate to predict the number of olfactory receptor genes that fossil mammals have. I confirmed their results and predicted gene counts in fossil whales, thereby documenting a decrease in the number of genes over the evolutionary transition from land to water. The relationships found in Bird et al. (2018) seem to hold in taxa other than Mammalia. My results pave the way for further study of the unique development of the respiratory tract of dolphins, assessment of the olfaction of baleen whales, and description of their evolutionary history.
J. G. M. Thewissen (Advisor)
Samuel Crish (Committee Member)
Mary Ann Raghanti (Committee Member)
Edgar Kooijman (Committee Member)
Tobin Hieronymus (Committee Member)
180 p.
Anatomy and Physiology; Animals; Biology; Evolution and Development; Histology; Morphology; Paleontology
ontogeny; ontogenetic series; cetology; Cetacea; cetacean; whale; dolphin; porpoise; olfactory receptor gene; olfactory neuroepithelium; nose; nasal cavity; ethmoturbinal; olfactory receptor neuron; cetaceans; olfactory marker protein; nasal; sense of smell; land to water transition; Artiodactyla; artiodactyl; even-toed ungulate; Cetartiodactyla

Recommended Citations

Citations

  • Farnkopf, I. C. (2022). The olfactory anatomy and upper respiratory tracts of whales, dolphins, and their terrestrial relatives: Perspectives from morphology, histology, embryology, and evolutionary biology [Doctoral dissertation, Kent State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=kent1653588212041775

    APA Style (7th edition)

  • Farnkopf, Ian. The olfactory anatomy and upper respiratory tracts of whales, dolphins, and their terrestrial relatives: Perspectives from morphology, histology, embryology, and evolutionary biology. 2022. Kent State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=kent1653588212041775.

    MLA Style (8th edition)

  • Farnkopf, Ian. "The olfactory anatomy and upper respiratory tracts of whales, dolphins, and their terrestrial relatives: Perspectives from morphology, histology, embryology, and evolutionary biology." Doctoral dissertation, Kent State University, 2022. http://rave.ohiolink.edu/etdc/view?acc_num=kent1653588212041775

    Chicago Manual of Style (17th edition)

kent1653588212041775
478
© 2022, all rights reserved.
This open access ETD is published by Kent State University and OhioLINK.