Olfactory epithelium and ontogeny of the nasal chambers in the bowhead whale (Balaena mysticetus).

Olfactory epithelium and ontogeny of the nasal chambers in the bowhead whale (Balaena mysticetus).

Farnkopf IC; George JC; Kishida T; Hillmann DJ; Suydam RS; Thewissen J G M

Anatomical Record

2021

2021-06-11

In a species of baleen whale, we identify olfactory epithelium that suggests a functional sense of smell and document the ontogeny of the surrounding olfactory anatomy. Whales must surface to breathe, thereby providing an opportunity to detect airborne odorants. Although many toothed whales (odontocetes) lack olfactory anatomy, baleen whales (mysticetes) have retained theirs. Here, we investigate fetal and postnatal specimens of bowhead whales (Balaena mysticetus). Computed tomography (CT) reveals the presence of nasal passages and nasal chambers with simple ethmoturbinates through ontogeny. Additionally, we describe the dorsal nasal meatuses and olfactory bulb chambers. The cribriform plate has foramina that communicate with the nasal chambers. We show this anatomy within the context of the whole prenatal and postnatal skull. We document the tunnel for the ethmoidal nerve (ethmoid foramen) and the rostrolateral recess of the nasal chamber, which appears postnatally. Bilateral symmetry was apparent in the postnatal nasal chambers. No such symmetry was found prenatally, possibly due to tissue deformation. No nasal air sacs were found in fetal development. Olfactory epithelium, identified histologically, covers at least part of the ethmoturbinates. We identify olfactory epithelium using six explicit criteria of mammalian olfactory epithelium. Immunohistochemistry revealed the presence of olfactory marker protein (OMP), which is only found in mature olfactory sensory neurons. Although it seems that these neurons are scarce in bowhead whales compared to typical terrestrial mammals, our results suggest that bowhead whales have a functional sense of smell, which they may use to find prey.

In their evolutionary transition from land to water, cetaceans (whales, dolphins, and porpoises) have adapted the anatomy of many of their organs (Berta, Ekdale, & Cranford, 2014; Thewissen, Cooper, George, & Bajpai, 2009; Uhen, 2010). Among these adaptations is a reduction of their olfactory anatomy related to the lesser importance of airborne stimuli in aquatic animals. This reduction is greater in odontocetes (toothed whales) than in mysticetes (baleen whales; Berta et al., 2014; Ichishima, 2016; Ries & Langworthy, 1937). Cetaceans must surface to breathe, and this could be an opportunity for mysticetes to sense airborne odorants.

Journal Article

NEOMED College of Medicine

Department of Anatomy & Neurobiology

Jan to Aug list 2021