Ultrastructure of the Pineal Gland of the Tropical Bat <i>Rousettus leschenaulti</i>

Abstract

The ultrastructure of the pineal organ was studied in the tropical megachiropteran Rousettus leschenaulti. The pineal lies deep beneath the hemispheres adjacent to the third ventricle and is traversed by the habenular commissure anteriorly. Its parenchyma consists of a uniform population of light and occasional dark pinealocytes which appear to differ only in the degree of cytoplasmic staining. Pinealocytes are characterized by well developed Golgi bodies associated with numerous small vesicles, many mitochondria and polyribosomes, and frequent subsurface cisternae. Lipid droplets and elements of smooth endoplasmic reticulum are scant. Cisternae of granular endoplasmic reticulum are occasionally dilated. A distinct feature is the abundance of clear vesicles in the pinealocyte pericapiUary terminals, which also frequently contain granular vesicles and a very large vacuole. The pineal is further characterized by the presence of a small number of glial cells and myelinated nerve fibers. A broad perivascular space investing numerous capillaries contains glial-cell and pinealocyte processes, collagen fibrils and abundant unmyelinated nerve fibers. Tortuous extensions of the perivascular space enter the pineal parenchyma where they come in close roximity to branched intercellular channels or canaliculi characterized by specialized junctions and microvilli. Differences between the pineal of the non-hibernating megachiropteran Rousettus and that of the hibernating microchiropteran bats, and structural similarities to the pineal of tropical rodents are discussed.

Ultrastructure of the pineal body of the common vampire bat, Desmodus rotundus

“…As a result, the ciliary precursors remain in a n arrested state of development. An occasional cilium extending in the widened intercellular space, as seen in Desmodus, in Rousettus (Chang et al, 1987)) and in the noctule bat (Pevet and Racey, 1977b), lends credence to the above hypothesis. Centrioles participate in cell division.…”

“…Such canaliculi have been reported not only in Rousettus pineal (Chang et al, 1987) but also in other animals (Quay, 1974; also see Vollrath, 1981). The canalicular system has been interpreted by Quay (1974) as linking the pinealocytes and blood vessels.…”

“…Unlike Rhinopoma (Bhatnagar et al, 1985 and Rousettus (Chang et al, 1987), in which both myelinated and unmyelinated nerve bundles have been reported in the pineal, only unmyelinated fibers are seen in Desmodus. This finding is in accordance with our earlier observations of the lack of myelinated bundles in those bat species in which the habenular commissure does not traverse through the pineal.…”

“…The few available ultrastructural studies on bats have involved the pteropodid Rousettus leschenaulti (Chang et al, 1987); hibernating vespertilionids, Nyctalus noc tula (Pevet et al, 1977a,b), Pipistrellus pipistrellus (PBvet and Racey, 19811, Vesperugo savi, and Vesperugo piccolo (Romita and Gatti, 1980;Gatti, 1982); rhinolophids (Stammer, 1972;Romita and Gatti, 1980); and the rhinopomatid Rhinoporna rnicrophyllurn (Bhatnagar et al, 1985-86). The order Chiroptera is composed of 18 families which are widely diversified in their feeding and habitat preferences, reproductive strategies, social behavior, echolocatory performance, and ecological specializations.…”

The ultrastructure of mammalian pinealocytes: A systematic investigation

“…Rabbit, Oryctolagus cuniculus McNulty and Hazlett, 1980Maria and Machado, 1987Samarasinghe and Delahunt, 1980Pevet and Saboureau, 1973 PBvet, 1974, 1977b PBvet and Collin, 1976Pevet and Kuyper, 1978Kikuchi et al, 1984Hwang, 1982 This study Chang et al, 1987;Bhatnagar et al, 1986Bhatnagar et al, , 1990 This study This study; Bhatnagar et al, 1986, 1990 Bhatnagar et al, 1985 This study…”