Morphology of the Malpighian Tubules of the Stink Bug Podisus nigrispinus (Heteroptera: Pentatomidae): Insights into Excretory Physiology of a Zoophytophagous Hemipteran

Abstract Zoophytophagous insects, such as Podisus nigrispinus (Dallas, 1851) (Heteroptera: Pentatomidae), play an important role in maintaining agroecosystem balance. However, the anatomy, histology, and ultrastructure of their Malpighian tubules remain poorly understood. This study aimed to describe these features in P. nigrispinus. Adults were dissected, and their Malpighian tubules were examined using light and transmission electron microscopy. Anatomically, P. nigrispinus possesses four convoluted Malpighian tubules that open independently at the junction between the midgut and ileum. The tubules are lined by a single layer of cuboidal epithelial cells, characterized by a well-developed apical brush border, cytoplasm rich in vacuoles, and a spherical nucleus with predominantly decondensed chromatin. Transmission electron microscopy revealed apical microvilli, numerous electron-lucent vesicles, spherocrystals with concentric contents, rough endoplasmic reticulum profiles, mitochondria, and autophagosomes. In the basal region, the plasma membrane displays long invaginations forming wide extracellular spaces closely associated with mitochondria. These structural features suggest high metabolic activity. This is the first detailed description of the Malpighian tubules in P. nigrispinus, contributing to a better understanding of the excretory physiology of zoophytophagous predatory Hemiptera.