Weberian apparatus

The Weberian apparatus is an anatomical structure that connects the swim bladder to the auditory system in fishes belonging to the superorder Ostariophysi.

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 third rib that interact directly with the anterior chamber of the swim bladder.

Specific studies have been done on the Weberian apparatuses of a few select taxa, including Danio rerio,[3] Rhaphiodon vulpinus[4] and Corydoras paleatus.

[5] The earliest recorded incidence of a Weberian apparatus is from the fossil fish Santanichthys diasii dating from the Early Cretaceous of Northeastern Brazil.

[6] An important feature within the formation of the Weberian apparatus, which is a synapomorphy of the Otocephala, is the attachment of the anterior Pleural cavity (rib) to the Swim bladder.

Another crucial feature is the anterior otophysic diverticula of the swim bladder and contacting the inner ear, seen in extant Clupeiformes.

This was shown by comparing the fiber of the ligament and the tunica externa of the swim bladder that have the same histological composition of elastin and icthyocoll (a specific type I collagen), as established in a research by Rui Diogo.