The cochlear nuclei in the common porpoise, Phocaena phocaena

• Published in: Journal of Comparative Neurology
• Main Authors: Osen, Kirsten Kjelsberg, Jansen, Jan
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1965
• Subjects: General Neuroscience; toothed whales
• Online Access: http://dx.doi.org/10.1002/cne.901250206; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fcne.901250206; https://onlinelibrary.wiley.com/doi/pdf/10.1002/cne.901250206

Abstract The structure of the primary cochlear nuclei in three specimens of the common porpoise, Phocaena phocaena , has been studied in transverse and sagittal sections stained for cells (Nissl) and myelin sheaths. A rudimental dorsal cochlear nucleus and a very large ventral cochlear nucleus were found. The large cochlear nerve (nine tenths of the entire VIII nerve) enters the rostral pole of the ventral cochlear nucleus within which it fans out to form ascending and descending fibers. Five subdivisions were distinguished in the ventral nucleus, viz., the anterior part, the posterior part, the dorsolateral part, the dorsomedial part, and the interstitial part. Great similarity exists between the Phocaena and other toothed whales with regard to the structure of the cochlear nuclei. Neither seems any principal difference to exist in this respect between the Phocaena and the landliving mammals, especially when compared with the primates which have likewise a poorly differentiated dorsal nucleus. The five subdivisions of the ventral nucleus of Phocaena presumably are the homologues of the subdivisions distinguished by Fuse ('13) and Lorente de Nó ('33) in the corresponding nucleus of terrestrial mammals. The enormous size of the ventral cochlear nucleus is the only reliable criterion observed that might reasonably be associated with the extraordinary sense of hearing in Cetacea.