Neuroanatomical Comparison of the Brain in Young and Adult Lesser Mouse-Tailed Bat, Rhinopoma hardwickii (Gray, 1831).

Bats are the sole group of mammals capable of flight, classified into Microchiroptera and Megachiroptera. This investigation aimed to study the morphology, anatomy, and histology of the Microchiropterans R. hardwickii brain at young and adult stages. Twelve adult and young bats were used. The gross anatomical aspects were examined. Brain tissue sections were prepared and stained using H&E, Nissl, toluidine blue, and immunohistochemically using GFAP antibody. The brain's dorsal view was pear-shaped, divided into forebrain (cerebrum), midbrain (is the most rostral part of the brainstem; pons and medulla oblongata), and hindbrain (cerebellum). A small, poorly developed olfactory bulb was observed. The cerebrum had a smooth surface with limited convolutions and depressions; it was divided into two hemispheres aligned along a median interhemispheric fissure. The pineal gland was distinctly visible. The optic lobes were prominent, rounded, and broad, appearing laterally on the midbrain. The hippocampus appeared as a dorso-medial protrusion separated by the lateral ventricle from the brain; it was well-developed in adult more than in young bats. The cerebellum was well-developed, partitioned into folds, and separated from the cerebrum by a slight transverse fissure. Histologically, a diminutive cerebral cortex was observed to have various types of neurons, including pyramidal, pyramidal-like, and multipolar. Hippocampal neurons were more extensive and lacked discrete layers. A comparatively more significant number of neurons was found in the cerebellum than in the cerebral cortex and other brain parts. All these previous characteristic features and neurological processes required for the generation and comprehension of vocalizations employed in echolocation of the Microchiropterans. Also, the findings of this study clarified notable neurological characteristics linked to the evolutionary connections and relationships of chiropterans.