The optic tectum of a perciform teleost II. Fine structure

Abstract

Abstract The fine structure of the six layers in the optic tectum of the teleost Eugerres plumieri has been studied with the electron microscope. In the stratum marginale, parallel nonmyelinated axons synapse on spines of thick dendrites of pyramidal cells, resembling the organization of the cerebellar cortex molecular layer. In the stratum opticum, two populations of fibers are described which differ in diameter, position and origin. In the stratum fibrosum et griseum superficiale, characteristic terminals belonging to optic nerve afferents are large and irregular, contain pale mitochondria with sparse cristae and large empty spaces, abundant round vesicles, and, occasionally, dense core vesicles. Optic nerve terminals synapse on pyramidal cells, as well as on dendritic profiles of other cell types, without a glomerular organization. Most cell types observed in Golgi preparations have been identified. Particular emphasis is placed on the description of different types of terminals and their synaptic relations.