Ipsilateral retinofugal and retinopetal projections in normal and monocular cichlid fish.

A previously unknown ipsilateral retinotectal projection in juvenile and adult cichlid fishes is revealed by anterograde labelling with horseradish peroxidase (HRP). Enucleation results in an enlarged ipsilateral projection from the intact eye; after 4 months this projection may cover the tectum almost completely. These data are interpreted as an increase in the normally occurring ipsilateral projection of newly differentiated ganglion cells due to the absence of interocular competition. Conversely, after enucleation cells of the homolateral thalamoretinal nucleus seem, on the basis of retrograde HRP staining to develop a new connection with the remaining eye.