Yuyun Wang, Xinyu Tang, Shunyan Dong, Zongbo Li
Tomicus yunnanensis, the most destructive pest in southwestern China, kills trees by predisposing the host for co-infestation by two sympatric species. Its survival relies largely on diverse capacities of its alimentary canal; thus, micro-computed tomography (micro-CT) and microscopic imaging reveal the morphology and topographical position of the gut, as well as the absence of sex-related differences in total length and regional organisation. The foregut, midgut, and hindgut account for 19.6%, 49.8%, and 30.6% of the total length, respectively. The crop is well developed and bears intimal spines, whereas the proventriculus is highly sclerotized, encircled by robust circular muscles and equipped with cuticular plates and teeth. The midgut is divided into anterior and posterior regions; only the latter possesses gastric caeca. The posterior midgut is structurally similar to the anterior midgut with respect to well-differentiated organelles, but exhibits longer microvilli and more abundant basal folds of the epithelial cells. A cryptonephridial system of six Malpighian tubules, arranged in two groups and attached distally to the anterior rectum, shows distinct proximal-distal structural differences. Epithelial folds forming microvillus-like structures, as well as microfibrils within the endocuticle, vary along the length of the hindgut. These findings are discussed in comparison with the alimentary canal of other Curculionidae (Coleoptera), with a particular focus on the Scolytinae.