Preliminary findings on the peripheral nervous system of the external ear in odontocetes

Cetacean mass strandings have been associated with exposure to high-energy anthropogenic noise, and the post-mortem investigations indicate pathologies related to such events. Although these kinds of exposure can trigger behavioural and physiological changes, the direct impact a low frequency and high intensity noise exposure can have on the physical tissues is still unclear, particularly regarding the acoustic pathways. Odontocetes can perceive sounds through their mandible and the associated acoustic fat bodies, which are in physical contact with the tympanic bulla and the ear bones. However, the exact pathway of how sound waves reach the inner ear is still under debate. Moreover, the involved tissues have been described in only few species, and as there are big interspecific differences in the acoustic spectrum, this constitutes interspecific morphological differences along the sound production and reception pathways. Furthermore, the function of associated tissues such as the external ear canal is unknown. Even if there is a general consensus amongst the scientific community that cetaceans could suffer from acoustic trauma after sound exposure, very scarce data is currently available to confirm this, especially during mass stranding events. Here, we will present the first stages of this project which involves the strategic partnerships between multiple international institutions involved in the assessment of the health status of vibration sensitive tissues in the head of small odontocetes. Furthermore, we will open up possibilities for more extended collaborations, and we will present preliminary results on the functional morphology of the peripheral nervous system related to the mentioned tissues.