The optic system of the teleost Cichlasoma biocellatum

The retinal projections of the fresh water teleost. Cichlasoma biocellatum, were examined using a modification of the Nauta‐Gygax method following unilateral enucleations and removal of retinal quadrants. After the unilateral enucleations, degeneration was found in the fasciculus medialis nervioptici, fasciculus geniculatus tractus optici, fasciculus dorsomedialis tractus optici, and the accessory optic tract. The pretectal nucleus, nucleus corticalis, and accessory optic nucleus contained debris of terminal degeneration. The majority of the optic fibers terminated in five layers in the optic tectum. The quadrant removals showed that fibers from the retinal quadrants formed layers in the ribbon shaped optic nerve running the width of the nerve. The dorsal to ventral arrangement of the fibers was: dorsal nasal quadrant; dorsal temporal quadrant; ventral nasal quadrant; and the ventral temporal quadrant. The fibers from only the posterior half of the retina supplied the fasciculus geniculatus tractus optici and the corpus geniculatum laterale. Fibers from the anterior half of the retina supplied the accessory optic tract and nucleus. All other tracts and nuclei examined received fibers from all the retinal quadrants. The projection of the retinal quadrants to the tectal quadrants was specific and always formed five layers of degeneration.