Anatomical measurements of dugong auditory systems for evoked potential studies (PDF)

Ketten, D.R., K. Lucke, and J. M. Lanyon

The Effects of Noise on Aquatic Life (2024)

DOI: 10.1007/978-3-031-10417-6_77-1

Dugongs (Dugong dugon) are listed globally as “Vulnerable to Extinction,” raising substantial concerns for their welfare. Underwater sounds are potentially critical survival cues for dugongs, but there are few data on dugong hearing, much less on how ambient sounds, natural or anthropogenic, may affect dugongs.

A project was undertaken in 2022 to obtain auditory evoked potential (AEP) responses in wild Australian dugongs during health assessments. In support of that study, a parallel effort investigated cranial and auditory system anatomy of dugongs to determine optimal placements of hydrophones for delivering sound stimuli and of the recording electrodes for AEP response measurements. Relevant anatomical measurements were obtained from computerized tomography (CT) imaging and dissection of three dugong specimens collected in a previous study of stranded dugongs from northern Australia in collaboration with Dr. Helene Marsh and Dr. Donna Kwan of James Cook University.

The study demonstrated three external landmarks that allow triangulation of surface points closest to the middle ear, inner ear, auditory nerve, and brainstem of dugongs. These anatomical landmarks are proportionately spaced across animals, allowing placement calculations for animals tested in field studies regardless of body mass, age, and sex.