A discrete projection of the sacculus and lagena to a distinct brainstem nucleus in a catfish

The projection of individual inner ear maculae of the catfish, Ancistrus spec. were labelled with horseradish peroxidases (HRP) or fluorescent dextran amines. In ostariophysans, fibres which innervate epithelia known or assumed to be sensitive to the pressure component of aquatic sound, i.e. acoustic fibres which come from the sacculus and lagena, have projections separate from those of the utriculus and canal organs. In Ancistrus afferents of sacculus and lagena terminate in an area which is distinct based on its cytoarchitecture. This area, previously believed to be a secondary auditory nucleus, is therefore an identifiable primary auditory nucleus in a subtetrapod vertebrate. This is different from other pressure sensitive teleosts (clupeids, osteoglossomorphs) in which acoustic fibres also terminate separately from vestibular fibres, but within parts of a larger cytoarchitectonic entity.