Weberian Apparatus

in fishes, an apparatus that senses, transforms into mechanical displacement, and transmits (by means of the movable element of the first vertebra and the cerebrospinal fluid) to the inner ear vibrations of the walls of the air bladder (sound resonator). It consists of four pairs of bones, movably articulated to one another, that connect the air bladder with the inner ear. The bones of the Weberian apparatus are modified parts of the first vertebrae and the third rib. The Weberian apparatus is named for the German anatomist E. Weber, who first described it in 1820. The degree of development of hearing in fishes is associated with the presence or absence of the Weberian apparatus. Fishes that have the Weberian apparatus (Cyprinidae, Siluridae, Characinidae, Gymnotidae) are capable of perceiving sounds with a frequency up to 13 kilohertz; fishes without the Weberian apparatus perceive sounds with a frequency up to 2.5 kilohertz.