Studies on the salivary glands of an aquatic bug,Lethocerus indicus(Belostomatidae): Morphological, histological and preliminary electron microscopic investigations

Abstract

AbstractA study was conducted to determine the morphology, histology and ultrastructure of the salivary apparatus ofLethocerus indicus. The apparatus was found to consist of a principal and accessory salivary gland. The former is bilobed, having a small superior lobe and a larger inferior lobe, made up of many lobules/acini. Each lobule is made up of a simple glandular layer of syncytial epithelium encompassing the lumen, which is filled with secretory granules that are elaborated from the epithelium predominantly by the apocrine mode of secretion. The accessory salivary gland is vesicular cum tubular. The vesicular part is made up of a thin layer of flat, polygonal cells, having no signs of secretory activity, while the tubular part consists of a single layer of columnar epithelial cells that show signs of secretory activity. Both the principal and accessory glands discharge their secretions through a common salivary duct which opens at the base of the hypopharynx. The ultrastructure of the lobules of the principal salivary gland reveals a thick amorphous, basement membrane (800–1000Å) which supports the glandular epithelium. The basal and apical plasma membranes of the epithelium show basal infoldings and microvilli respectively. The nucleus is highly branched and remains surrounded by a double layered nuclear envelope. The ergastoplasmic membranes show abundance of ribosomes. Many mitochondria are also visible in the cytoplasm. It is concluded that the salivary gland ofL. indicusis an organ of high synthetic activity.