Bilateral retinal projections in the black piranha (Serrasalnus niger).

The retinal projections were studied in the black piranha (Serrasalmus niger) with degeneration and autoradiographic methods. The projections are bilateral to the hypothalamic optic nucleus, the dorsomedial optic nucleus, corpus geniculatum ipsum of Meader (1934) and the optic tectum. Unilateral, crossed projections were traced to the pretectal nucleus and the cortical nucleus. The visual system of the black piranha is exceptionally well developed but has retained many primitive features including the extensive bilateral projections.