Histology and Immunofluorescence Analyses in the Brain of Reeves' Turtle (Mauremys reevesii)

This study investigated the histological structure of the Mauremys reevesii brain using hematoxylin-eosin (HE) staining and examined the localization and expression of Pax6 in the brain through immunofluorescence staining.The HE staining results revealed the histological structures in the olfactory bulb, cerebrum, diencephalon, mesencephalon, cerebellum and medulla oblongata of M. reevesii.The olfactory bulb could be divided into seven layers from the outer to the inner region.The cerebral cortex consisted of three layers.The optic tectum of mesencephalon comprised six distinct layers.The cerebellar cortex exhibited a three-layered organization.In M. reevesii, while the thalamus and medulla oblongata lacked distinct laminar organization, they contained numerous nuclei.Immunofluorescence staining revealed widespread distribution of Pax6-immunoreactive (Pax6-IR) cells in the brain of M. reevesii.In the olfactory bulb, Pax6-IR cells were densely distributed in the glomerular layer.Within the telencephalon, these cells showed the highest density and strongest fluorescence intensity in the dorsal septum.In the diencephalon of M. reevesii, the prethalamus contained extensive Pax6-IR cell populations.Within the mesencephalon, prominent Pax6 immunoreactivity was observed in the tegmentum.In coronal sections, continuous Pax6-IR cells were prominently distributed along the dorsal medulla oblongata near the alar plate region of the fourth ventricle.In the cerebellum, extensive Pax6 immunoreactivity was observed in both the medullary layer and granular layer, albeit with weaker fluorescence intensity.