title: Ultrastructure of the Odontocete organ of Corti: scanning and transmission electron microscopy.
abstract: The morphological study of the Odontocete organ of Corti, together with possible alterations associated with damage from sound exposure, represents a key conservation approach to assess the effects of acoustic pollution on marine ecosystems. By collaborating with stranding networks from several European countries, 150 ears from 13 species of Odontocetes were collected and analyzed by scanning (SEM) and transmission (TEM) electron microscopy. Based on our analyses, we first describe and compare Odontocete cochlear structures and then propose a diagnostic method to identify inner ear alterations in stranded individuals. The two species analyzed by TEM (Phocoena phocoena and Stenella coeruleoalba) showed morphological characteristics in the lower basal turn of high-frequency hearing species. Among other striking features, outer hair cell bodies were extremely small and were strongly attached to Deiters cells. Such morphological characteristics, shared with horseshoe bats, suggest that there has been convergent evolution of sound reception mechanisms among echolocating species. Despite possible autolytic artifacts due to technical and experimental constraints, the SEM analysis allowed us to detect the presence of scarring processes resulting from the disappearance of outer hair cells from the epithelium. In addition, in contrast to the rapid decomposition process of the sensory epithelium after death (especially of the inner hair cells), the tectorial membrane appeared to be more resistant to postmortem autolysis effects. Analysis of the stereocilia imprint pattern at the undersurface of the tectorial membrane may provide a way to detect possible ultrastructural alterations of the hair cell stereocilia by mirroring them on the tectorial membrane.
authors.affiliation: Laboratory of Applied Bio-Acoustics, Technological Center of Vilanova i la Geltrú, Technical University of Catalonia-Barcelona Tech, 08800, Vilanova i la Geltrú, Barcelona, Spain; Zoology Department, The University of British Columbia, V6T 1Z4 Vancouver, Canada.
authors.forename: Maria
authors.initials: M
authors.lastname: Morell
authors.forename: Marc
authors.initials: M
authors.lastname: Lenoir
authors.forename: Robert E
authors.initials: RE
authors.lastname: Shadwick
authors.forename: Thierry
authors.initials: T
authors.lastname: Jauniaux
authors.forename: Willy
authors.initials: W
authors.lastname: Dabin
authors.forename: Lineke
authors.initials: L
authors.lastname: Begeman
authors.forename: Marisa
authors.initials: M
authors.lastname: Ferreira
authors.forename: Iranzu
authors.initials: I
authors.lastname: Maestre
authors.forename: Eduard
authors.initials: E
authors.lastname: Degollada
authors.forename: Gema
authors.initials: G
authors.lastname: Hernandez-Milian
authors.forename: Chantal
authors.initials: C
authors.lastname: Cazevieille
authors.forename: José-Manuel
authors.initials: JM
authors.lastname: Fortuño
authors.forename: Wayne
authors.initials: W
authors.lastname: Vogl
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Puel
authors.forename: Michel
authors.initials: M
authors.lastname: André
mesh_terms: D000818:Animals; D004423:Ear / Q000033:anatomy & histology; D006198:Hair Cells, Auditory / Q000648:ultrastructure*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D009925:Organ of Corti / Q000648:ultrastructure*; D019576:Porpoises; D013045:Species Specificity
keywords: acoustic trauma; cetacean; cochlea; inner ear; morphology