Weberian Apparatus - Embryology

Embryology

Embryonic analysis of Weberian apparati of the taxon Brycon has shed some light on the development of the structure itself. The Weberian apparatus elements form from the fully distinguishable first five vertebrae of the individual. The supraneural starts as an element of the skull. The claustra and the scaphia develop from expanded elements of the neural arch of the first vertebrae (V1). From the second vertebrae (V2), the intercalarum and the vertebrae's lateral process are reduced and clump together. The plural rib (R1) of the third vertebrae (V3) shrinks and moves somewhat ventrally, forming the tripus from a vertebral parapophysis fusing with the pleural rib. The os suspensorium bone of the fourth vertebrae (V4) somewhat retains its shape, developing from the pleural rib of the vertebrae (R2). The remaining elements of the fifth vertebrae (V5), the parapophysis and the articulating rib (R3), including the vertebrae itself form the posterior structure of the Weberian apparatus. The neural spines of the first four vertebrae fuse and compress, forming one of the major structures of the apparatus.

Study of the embryology of the Weberian apparatus has since been conducted on various other ostariophysan species. The results of which have resulted in various interpretations of the development (and thus the homology) of the structures that form the structure. Specific studies have been done on the Weberian apparati of a few select taxa, including Danio rerio, Rhaphiodon vulpinus and Corydoras paleatus.