Pinealocytes and Glia Cells in the Pineal Gland of the African Straw-Coloured Fruit Bat (Eidolon helvum)

Abstract

Abstract The mammalian pineal gland is a structure that in recent years has been extensively studied, due to its functions and the hormones it produces. Bats are the only known flying mammals, with the order having a large number of species. This study was carried out to investigate the gross and histological features of the pineal gland of the Eidolon helvum, the African fruit bat, using male and female subjects. Eight free flying E. helvum (4 males, 4 females) were captured using mist nets. The pineal gland was grossly observed to be very small in size, oval in shape, and covered by the pia mater. Histological examination revealed two populations of pinealocytes – Types I and II – oval structures possessing acidophilic cytoplasm and large, round nuclei. Pinealocytes were seen to appear singly or in clusters, having no particular arrangement. Sexual dimorphism was observed, with the females having less density in population of pinealocytes at the peripheral region of the gland. This was consistent in all subjects examined. Astrocytic appearance was typical with long and slender processes, and perivascular and capsular microglia were observed. The glia cells were observed to be abundant in the parenchyma and around the capsule. There was no sensitivity to NeuN antibody. Results obtained may find application in behavioural and comparative neuroscience.