Ultrastructure of the Anterior Midgut in the Balsam Woolly Adelgid (Homoptera: Adelgidae) in Relation to Excretion

Abstract

The epithelial cells of the anterior midgut in adult Adelges piceae (Ratzeburg) were examined with light and electron microscopy and x-ray microanalysis. The large conical epithelial cells are characterized by extensive basal membrane infoldings often associated with mitochondria and well-developed microvilli projecting into the anterior midgut lumen. The cytoplasm contains abundant mitochondria, rough endoplasmic reticulum, free ribosomes, vesicles, and vacuoles, but Golgi complexes are sparse. Numerous electron-dense and laminate concretions rich in iron, silicon, chlorine, calcium, magnesium, manganese, and sulfur are scattered throughout the cytoplasm. The concretions appear to be formed in the cisternae of rough endoplasmic reticulum. The dual role of the anterior midgut epithelial cells in the synthesis of digestive enzymes as well as in the storageexcretion of mineralized concretions is discussed.