Selective Inner Hair Cell Loss in a Neonate Harbor Seal (Phoca vitulina)
Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover, Foundation, 25761 Büsum, Germany
Zoology Department, The University of British Columbia, Vancouver, BC V6T 1Z4, Canada
Faculty of Veterinary Medicine and Zootechnics, National Autonomous University of Mexico, Av. Universidad 3000, Delegación Coyoacán, Mexico City 04510, Mexico
Vancouver Aquarium Marine Science Center, Vancouver, BC V6G 3E2, Canada
Department of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, 22529 Hamburg, Germany
Animal Health Center, Ministry of Agriculture, Abbotsford, BC V3G 2M3, Canada
Author to whom correspondence should be addressed.
Academic Editor: Catarina Eira
Received: 22 December 2021
Revised: 6 January 2022
Accepted: 7 January 2022
Published: 12 January 2022
Congenital hearing loss (i.e., hearing impairment present at birth) is recognized in humans and other terrestrial species, but there is a lack of information on congenital malformations and associated hearing loss in pinnipeds (seals, sea lions, and walruses). Baseline knowledge on marine mammal inner ear malformations is essential to differentiate between congenital and acquired abnormalities, which may be caused by infectious agents, age, or anthropogenic interactions, such as noise exposure. Analysis of the cochlea of a neonate harbor seal (Phoca vitulina) revealed bilateral loss of inner hair cells (sensory cells responsible for transducing the auditory signal) while the outer hair cells (sensory cells responsible for sound amplification and frequency selectivity and sensitivity) were intact. The selective inner hair cell loss (up to 84.6% of loss) was more severe in the basal turn, where the high frequencies are encoded. Potential causes and consequences are discussed. This is the first report of a case of selective inner hair cell loss in a marine mammal neonate, likely congenital.