Structural organization of the optic tectum of Barbus meridionalis Risso. I: Inner strata (SPV, SAC and SGC)

: The histological features of the three deepest strata of the Optic Tectum of Barbus meridionalis were studied with several staining and impregnation techniques. The boundaries between SPV, SAC and SGC were easily established and furthermore the myelinization pattern of the SAC is described. Several neuronal types were distinguished according to their dendritic and axonal features. Pyriform multipolar neurons were found in the SPV; in the SAc, pear-shaped, horizontal and multipolar neurons; in the SGC, fusiform, horizontal, multipolar and pyriform neurons. Some of the pyriform neurons of the SAC are described with axonal characteristics which has allowed us to consider these neurons as a new type of efferent tectal neuron.