In 1820, WEBER described the Weberian apparatus which characterises the Characins group of fish (carps, minnows tetras etc.). The Weberian apparatus is a linkage of bones called ossicles, derived from the vertebrae immediately following the skull, connecting the inner ear and the swim bladder which enables the fish to hear high frequency sounds, sense danger and form shoals for protection.

The swim bladder serves as a resonating chamber and the bony connection amplifies the sounds and transmits them to the skull, where they are detected by the inner ear. This effectively magnifies sound and enables Characins to hear frequencies much higher than most other fish.