Asymmetry of the habenulae in the elasmobranch "Scyllium stellare". I. Light microscopy.

The habenular nuclei of the elasmobranch "Scyllium stellare" have been studied with conventional histological techniques for light microscopy. Their left-right asymmetry has been defined by the observation of serially cut sections. In addition, their cytoarchitectonic organization has been defined quantitatively. In all specimens observed, the left habenula was larger, longer and richer in myelin than the right. However, it appears that the right habenula is subdivided into more subnuclei than the left. We hypothesize that the morphologic asymmetry of the habenulae might reflect a functional specialization of the two sides of the epithalamus.