Morphological features of the nasal cavities of hawksbill, olive ridley, and black sea turtles: Comparative studies with green, loggerhead and leatherback sea turtles.

Shogo Murakami,Akihiro Kaji,Chiyo Kitayama,Taketeru Tomita,Yuki Aiko,John A B Claydon,Yusuke K Kawai,Daisuke Kondoh,Keiichi Ueda,Hiroyuki Suganuma,Shingo Fukada,Satomi Kondo,Atsuru Fujimoto,Yoshiaki Tanaka,Mariko Omata,Masashi Yanagawa

doi:10.1371/journal.pone.0250873

Abstract

We analyzed the internal structure of the nasal cavities of hawksbill, olive ridley and black sea turtles from computed tomography images. The nasal cavities of all three species consisted of a vestibule, nasopharyngeal duct and cavum nasi proprium that included anterodorsal, posterodorsal and anteroventral diverticula, and a small posteroventral salience formed by a fossa of the wall. These findings were similar to those of green and loggerhead sea turtles (Cheloniidae), but differed from those of leatherback sea turtles (Dermochelyidae). Compared to the Cheloniidae species, the nasal cavity in leatherback sea turtles was relatively shorter, wider and larger in volume. Those structural features of the nasal cavity of leatherback sea turtles might help to suppress heat dissipation and reduce water pressure within the nasal cavity in cold and deep waters.

Highlights

This study was conducted from the standpoint that black turtles are a subspecies of green turtles, because we focus on their morphology
The cavum nasi proprium consists of significant anterodorsal, posterodorsal and anteroventral diverticula, and a small posteroventral salience formed by a fossa on the wall
The cavum nasi proprium of all three of these species comprised anterodorsal, posterodorsal and anteroventral diverticula, and a small posteroventral salience formed by a fossa on the wall, and the relative size of the olfactory region to the cavum nasi proprium was similar among sea turtle species

Summary

Introduction

There are seven sea turtle species; green (Chelonia mydas), loggerhead (Caretta caretta), hawksbill (Eretmochelys imbricata), olive ridley (Lepidochelys olivacea), Kemp’s ridley (L. kempii), flatback (Natator depressus), and leatherback (Dermochelys coriacea) [1]. Due to a distinctive appearance, some green turtles are often referred to as black sea turtles (C. mydas agassizii). While these morphological differences have led to the suggestion that black sea turtles are a distinct subspecies [2], categorization as such is still under discussion, and the Turtle Taxonomy Working Group [1] concluded that genetic analyses [3] do not indicate that black.

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Conclusion