Weberian Apparatus - Structural Anatomy and Function

Structural Anatomy and Function

The generalized structure of the Weberian apparatus is akin to a skeletal complex of bones and ossicles that are physically connected to the labyrinth auditory complex anteriorly and the anteriormost region of the swim bladder posteriorly. The entire structure is derived from skeletal elements of the first four vertebrae. The involved elements include: The supraneural bones of the skull; modified neural arch bones, specifically the paired claustra and the scaphia; The intercalarium and the lateral processes; The tripus; The os suspensorium from the fourth vertebrae; The parapophysis of vertebrae #5 including the vertebrae itself, plus the vertebrae's corresponding pleural rib. In addition, a structure composed of fused neural spines form the dorsalmost part of the Weberian apparatus. Together, the structure interacts anteriorly with the lagenar otolith set within the skull and posteriorly with the swim bladder via the pleural rib. Postero-ventrally, it is the tripus, the os suspensorium and the 3rd rib that interact directly with the anterior chamber of the swim bladder.

The Weberian apparatus functions by transmitting auditory signals straight from the gas bladder, through the Weberian ossicles and then straight into the labyrinth structures of the inner ear. The structure essentially acts as an amplifier of sound waves that would otherwise be only slightly perceivable by the inner ear structure alone. With the added function of the swim bladder as a resonating chamber, signals are amplified to noticeable levels.