Fine Structural Characteristics and the Regulatory Mechanisms of Adrenal-Cortical Region of Adult Male Fruit Bat, Rousettus leschenaulti (Desmarest)

Abstract

The present paper describes the fine structural characteristics of the adrenal-cortical region of adult male fruit bat Rousettus leschenaulti. The functional significance of the secretions of the adrenal-cortical region in reproduction is discussed. This study was carried out in the Indian fruit bat R. leschenaulti (Desmarest) because of the unique aspects of reproduction of this animal. It shows two breeding cycles, one in the autumn and the other in the spring. The adrenal gland of Rousettus undergoes remarkable cyclical changes in relation to the reproductive cycle. The cortex and medulla are clearly demarked. During the inactive and pre-breeding period, the zona glomerulosa is made up of polyhedral cells arranged in the form of acini. On the other hand during the breeding period it is highly vascularized. It is composed of compactly arranged dark and light polyhedral cells. Smooth endoplasmic reticulum in the form of circular vesicles, is well developed during breeding phase. The zona fasciculata is a larger zone in the cortex. During inactive period, it is made up of polyhedral cells and during pre-breeding and breeding periods cells are polygonal in shape with spherical nucleus. The zona fasciculata is richly vascular during the breeding period. The cells of zona fasciculata during the breeding period have prominent smooth endoplasmic reticulum. Mitochondria, with tubular and vesicular cristae and a large number of lipid droplets, suggest increased rate of synthetic activity. The close association of smooth endoplasmic with mitochondria and lipid droplets indicate that these cells are actively involved in steroid biosynthesis. Steroidogenic organelles are well developed in the cells of reticularis during the inactive prebreeding and active breeding period. All these organelles suggest that cells of glomerulosa are active in synthesizing steroid hormones. The cisternae of smooth endoplasmic reticulum lie close to the nucleus, mitochondria and lipid droplets. This association most likely represents the conversion of steroids to lipid droplets for storage or the reverse trend indicates removal of sterol for steroidgenesis.