Morphology and histology of the alimentary canal, salivary glands and Malpighian tubules in Pyrrhocoris apterus (Linnaeus, 1758) (Hemiptera: Pyrrhocoridae): a scanning electron and light microscopies study

Abstract

In this study, morphological and histological studies of the alimentary canal and associated salivary gland and Malpighian tubules were conducted for the firebug Pyrrhocoris apterus (Hemiptera: Pyrrhocoridae), which is their diets are mainly linden trees and mallows. Understanding its digestive process will help elucidate the ecological and economical significance of this species. Therefore, the insects were dissected to examine all the sections under stereomicroscope, light and scanning electron microscopies. Morphological and histological results show that the salivary glands of P. apterus find in the thorax of the insect with a pair of principal glands, a pair of accessory glands, a pair of principal canals and a pair of accessory canals. The alimentary canal is divided into three regions: foregut, midgut, and hindgut. The foregut consists of oral cavity, pharynx, esophagus, and proventriculus. The esophagus consists of a long tube and is surrounded by a layer of longitudinal muscle. The proventriculus is formed by a single layer of columnar cells with oval nuclei surrounded by a layer of muscles. The midgut is divided into four regions: the first, second, third, and fourth ventriculi. The midgut is composed of monolayer epithelial cells surrounded by muscles. P. apterus midgut lacks gastric caeca. The hindgut has a pylorus followed by a well-developed rectum. The wall of the rectum is surrounded by a single layer cubic epithelium which has deep infoldings. There is a pair of Malpighian tubules linked at each side of mediolateral of pylorus. Malpighian tubules consist of two regions as proximal and distal. Malpighian tubules consist of a monolayer cuboidal epithelium with cubic nuclei in middle.