Abstract
In this review, I aim to introduce recent progress towards understanding the evolution of auditory organs in animals. Despite of 600 million years of separation of protostomia and deuterostomia, key genes needed for the development, the nature of mechanoreceptive channels, and the amplification mechanism in sensory neurons are shared between vertebrate ears and insect ears. These findings argue against the previously prevailing view that vertebrate and invertebrate ears have separate evolutionary origins. Anatomical, developmental, and molecular genetic studies consistently show that the auditory organs in insects are derived from unspecialized, low-vibration-sensitive chordotonal organs. Thus, any chordotonal organs in body appendages could evolve into auditory organs. Convergent evolution of auditory organs, therefore, is based on the specialization of the sound transmission apparatus (e.g. tympanum, tracheal expansion) rather than on the sensory neurons.
