Descripción histológica de los núcleos de la vía electrosensorial central en el encéfalo de la especie Sternopygus aequilabiatus (Humboldt, 1811) (Gymnotiformes: Sternopygidae)

Abstract

Sternopygus aequilabiatus is a wave-type electric fish belonging to the order Gymnotifomes. It is distributed mainly in the trans-Andean regions of South America. In the present work the nuclei of the central electrosensory pathway of the encephalon of the electric fish Sternopygus aequilabiatus (Gymnotiformes: Sternopygidae) are histologically described, through the analysis of histological sections and macrophotographs. For the realization of the cuts, three adult individuals were collected. The histological sections were stained with hematoxylin-eosin. We identified the brain regions that are directly related to the electrosensory system (Neuronal nuclei responsible for the discharge of the electric organ, DOE), and compared them with the encephalon of wave-like electric fish species (Eigenmannia virescens, Sternopygus macrurus, Apteronotus leptorhynchus, A. albifrons,) previously reported. The cytoarchitecture of 13 electrosensory nuclei was analyzed and compared with the same nuclei present in Eigenmannia virescens, Sternopygus macrurus, Apteronotus leptorhynchus, A. albifrons. No differences were found in the histological organization of the nuclei, except in the medullary pacemaker nucleus (PM) that is found internally in the oblong medulla in S. aequilabiatus. In most of the nuclei a great vascularization not reported for the other species mentioned above was found. In general, the cytoarchitecture of the electrosensory nuclei is conserved in the different species of Gymnotiformes, however, there are differences in the size, number and shape of the neurons. In future studies of electrosensory structures of electric fish, it is recommended to perform immunohistochemical tests to establish the synapse between the layers and the afferents and eferences of the electrosensory pathway.