Abstract
Simple SummaryThe developmental anatomy of the dolphin head has been studied mostly in single fetuses and few works have been made using a wide range of specimens. In this study, fetal specimens are the main subjects, but newborn, juvenile and adult specimens were also used. Our study analyzes the external nose and nasal cavities during pre- and postnatal development. The nose and nasal cavities were studied using a high-resolution endoscopy to analyze changes in the mucosa of fetal specimens, newborns and juveniles. Magnetic Resonance Imaging (MRI) was also used in fetuses to locate and identify significant structures. Computed Tomography (CT) allowed us to understand the development of the facial bones and the nasal cavity. The histological samples were compared with a horse, a terrestrial mammal with a complex nasal anatomy. Dissections and anatomical sections in two spatial planes were compared with MRI and CT studies. Endoscopy of the external nose showed interesting morphological changes as only two different diverticula (air sacs) were observed in the vestibular part and one recess in the respiratory and olfactory part. We conclude that nasal cavity development of the striped and common dolphins and the pilot whale is simpler than in the bottlenose dolphin and the melon is part of the nose both anatomically and functionally.Our goal was to analyze the main anatomical structures of the dolphin external nose and nasal cavity from fetal developmental stages to adult. Endoscopy was used to study the common development of the external nose and the melon, and nasal mucosa. Magnetic resonance imaging (MRI) and anatomical sections were correlated with anatomical sections. Computed tomography (CT) was used to generate 3D reconstructions of the nasal bones and nasal cavities to study its development. Dissections, histological and pathological studies were carried out on the nasal mucosa to understand its function. These results were compared with the horse. Endoscopy showed an external nose with two lips and the upper lip is divided by a groove due to the nasal septum and an obstruction of right nasal cavity was diagnosed in a newborn. Two diverticula (air sacs) were found in the nasal vestibule and an incisive recess (premaxillary sac) in the nasal cavity. These findings were corroborated by 3D reconstructions of the nasal cavities, MRI, anatomical sections and dissections. The presphenoid and ethmoid bones were fused at early stages of fetal development. The ethmoid is the last bone to ossify in the nasal cavity.
Highlights
Through evolution, mammals that colonized the aquatic environment have undergone numerous adaptations in their anatomical structures, especially those of the cephalic region [1]
The endoscopic figures are described by columns, observing in the left column the external nose closed in its natural position to avoid the entrance of amniotic liquid into the lungs
In the third common dolphin (Delphinus delphis) fetus (4.5 months gestation) the epidermis of the external nose differs from the forehead epidermis, with a different colour and with a clear separation edge of the upper lip and the forehead skin
Summary
Mammals that colonized the aquatic environment have undergone numerous adaptations in their anatomical structures, especially those of the cephalic region [1] These adaptative changes are mainly seen in the asymmetry and telescoping of the skull [2,3,4] and have direct implications in feeding [5], mechanical protection of cephalic structures, echolocation, breathing and diving. There are not many articles in the scientific literature about the cetacean upper respiratory system, and some of the existing studies differ in their descriptions of structures and the terminology used to identify these structures Most of those articles are about adult specimens, either odontocetes [11,12,13,14,15,16,17,18,19,20] or mysticetes [21,22,23,24] and many of them focused on sound production and biosonar [14,25,26]. Endoscopy is commonly used in dolphin medicine especially to view the lower respiratory tract (lungs and bronchus) [33,34,35,36,37] but is not often used to visualize the nasal passages, a region of key importance, in live animals, and during necropsies to confirm any pathology incompatible with a correct air passage and likely to interfere with vital activities such as diving and feeding that will decrease the life expectancy of the animal
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
