Estudo morfológico do encéfalo de répteis (chordata: reptilia)

Abstract

The transition period from the aquatic to the terrestrial environment involved the development of a greater degree of activity, and the regions of the brain of the reptiles, most affected by these changes, were the telencephalon, thalamus, optic tectum, and cerebellum. The purpose was to identify and map morphologically, internally and externally, the regions of the encephalon in different species of reptiles (Podocnemis expansa, Podocnemis unifilis, Phrynops geoffroanus, Melanosuchus niger, Bothrops jararaca e Salvator merianae) and of embryos of Podocnemis expansa. Young reptilian species, and artificially incubated P. expansa eggs were used until stage 25, and later performed euthanasia and brain withdrawal. For macroscopic analysis, the brains were fixed in formaldehyde, and for the microscopic of the embryos, cryophores were made semiseriate and stained with eosin and contracted with Nissl. The brain of these animals presented smooth, composed by olfactory bulbs, cerebral hemispheres, diencephalon, mesencephalon, cerebellum, pontine tegmentum and medulla. The telencephalic pallium is formed by the lateral, dorsal, medial pallium and region of the amygdala. The lateral pallium is formed by the lateral córtex, located dorsolateral to the dorsal ventricular ridge. The amygdala is formed by groups associated with the olfactory system. The dorsal pallium is formed by the dorsal cortex, the lateral part of the dorsal cortex and the dorsal ventricular ridge, located deep in the lateral ventricle. The medial pallium is organized by the medial cortex, the dorsomedial cortex and two amygdalar nuclei. The subpalium consists of the striated complex, the striated part of the amygdala and the septum. The diencephalon is formed by epithelium, hypothalamus, dorsal and ventral thalamus. The midbrain presents the optic tectum, the semicircular torus, and the isthmus. There is no separation between the mesencephalic tegment and the pontine tegmentum, both forming the tegmentum, and its nuclei are located in the region of the floor of the midbrain, ventral to the medulla. The cerebellum is formed by the cerebellar cortex and a layer of white matrix. The medulla presents the emergence of the cranial nerves V to XII. It was concluded that in B. jararaca there is the presence of fourth ventricle and internal choroid plexus, rudimentary cerebellum, and absence of the accessory nerve (XI), and the embryos have a prominent dorsal ventricular ridge, and tegmental nuclei in the region of the medulla.