First insights into histological and ultrastructural organization of midgut and Malpighian tubules in mole crickets Gryllotalpa gryllotalpa Linnaeus, 1758 (Orthoptera: Gryllotalpidae).

Despite the economic crises caused by the mole cricket, Gryllotalpa gryllotalpa, as a critical agricultural pest, the detailed structural organization of its digestive and excretory systems has not yet been studied. In this work, we probed, for the first time, the structural organization of the gastric caeca, the anterior segment of the hindgut, and the Malpighian tubules of G. gryllotalpa collected from Egypt using light, scanning, and transmission electron microscopy. Histological analysis substantiated the macroscopic morphological observations of the midgut of G. gryllotalpa to be confined to a pair of gastric caeca, followed by a tubular mesenteron lined by a cuticular layer. The gastric caeca emerged as epithelial folds consisting of columnar cells, regenerative nidi within a unique niche-like structural organization, developing cells, and principal secretory cells. Scanning electron microscopy further revealed numerous enterocytes protruding into the lumenal surface of the midgut, with distinct cell boundaries covered by well-organized microvilli. Additionally, the midgut epithelium showed several cytoplasmic protrusions, along with remnants of the peritrophic matrix. Ultrastructural observations of Malpighian tubules exhibited a conserved epithelial organization, characterized by a monolayered epithelium, prominent basal membrane folding associated with abundant mitochondria, spherites, and an apical microvillar surface. Interestingly, energy-dispersive X-ray (EDX) results demonstrated that calcium (Ca) is the predominant element in spherites within Malpighian tubules, followed by phosphorus (P), with minor concentrations of zinc (Zn), potassium (K), and iron (Fe). Our findings provide comprehensive histological and ultrastructural insights into the digestive and excretory systems of G. gryllotalpa. Moreover, the current research provides crucial baseline data for future comparative investigations and for assessing the potential pesticidal effects of various novel pest-control strategies on digestive architecture.