Structural organization of the cerebral cortex of the neotropical lizard Tropidurus hispidus

Abstract

Lizards belonging to the Tropiduridae family are “sit-and-wait” foragers, relying mainly on visual identification to catch prey that cross their visual fields. Little is known about the neurobiology of Tropiduridae lizards. We have used neurohistological techniques to study the structural organization of the telencephalon of the neotropical lizard Tropidurus hispidus, paying special attention to the cerebral cortex. As revealed by the Nissl technique and Golgi staining, the telencephalon of T. hispidus follows the squamate pattern, with some differences: the lateral cortex appears relatively atrophic, and most of the neuronal somata of the dorsal cortex are dispersed without forming a conspicuous cell layer. Golgi staining has revealed ten different neuronal types in the three cortical layers, based on somata shape and dendritic morphology: the granular (unipolar, bipolar, and multipolar), pyramidal (normal, inverted, open, bipyramidal, and horizontal), spherical horizontal, and fusiform neuronal types. The axon direction could be traced in five of the subtypes. We have also studied the distribution of zinc-enriched terminals in the telencephalon of T. hispidus by the Neo-Timm method. Some portions of the cortex, septum, striatum, and amygdaloid complex stain heavily, with patterns resembling those described for other lizard families. Thus, T. hispidus appears to be an interesting representative of the Tropiduridae family for further neurobiological comparative studies.