The external and middle ear of the striped dolphin Stenella coeruleoalba (Meyen 1833).

The ear of cetaceans, and especially the middle ear, is very different from that of terrestrial mammals and shows specific adaptations to diving. Our research, performed on six Striped dolphins (Stenella coeruleoalba) stranded along the Italian coasts of the Mediterranean Sea, concentrated on the morphology of the external and middle ear of this species. We report the findings using a proper Veterinary Anatomical Nomenclature and describe the characteristics of the auditory meatus of the external ear and the presence and morphology of the erectile tissue in the middle ear. Our anatomical and histological data highlight the structure and possible functions of the corpus cavernosum located in the middle ear of the Striped dolphin, and suggest a possible role for this structure in relation to pressure regulation during diving. Many of our observations indicate the existence of an internal regulatory system able to prevent barotraumas by regulating pressure and volume inside the middle ear cavity.