The development of hearing abilities in the shark Scyliorhinus canicula.

The few works on audition in sharks and rays concern only adult specimens. We report the hearing abilities in the dogfish Scyliorhinus canicula at different stages, from embryos that still have their yolk sac inside their egg, to juveniles. Hearing development corresponds to an increase in the frequency range from 100-300 Hz in early pre-hatching stages to 100-600 Hz in juveniles. Modifications in hearing abilities correspond to the development of the brain, the increase of the volume of the membranous labyrinth, the growth of the sensory epithelium, and the development of stereocilia in addition to kinocilium before hatching. This work offers solid insights into the development of hearing abilities that usually can only be inferred from the anatomy of vertebrates or after birth/hatching. It shows also that shark can be sensitive to background noise during development.