Morphological and ultrastructural characterization of the alimentary canal in larvae of Streltzoviella insularis (Staudinger) (Lepidoptera: Cossidae)

Abstract

Streltzoviella insularis (Staudinger) is an important tree‐boring pest, that primarily damages Sophora japonica (Linnaeus) and Ginkgo biloba (Linnaeus), as well as other common species, at great economic cost to the urban landscape construction industry in China. In the present study, the alimentary canal morphology of S. insularis was observed using light microscopy, and its ultrastructure was investigated by scanning and transmission electron microscopy. The foregut of S. insularis can be divided into the pharynx, esophagus, crop, proventriculus, and cardiac valve. The well‐developed crop forms the longest section of the foregut. It is able to store large amounts of food and is lined with a monolayer of epithelial cells. Many sclerotized microspines occur on the surface of the anterior intima and there are dense spines on the posterior intima of the proventriculus. Epithelial cells of the midgut include columnar cells, goblet cells, and regenerative cells, but endocrine cells are absent. The hindgut consists of the pyloric valve, ileum, and rectum. There is no clear distinction between the ileum and colon. The intima surface of the pyloric valve carries many microspines, whereas the intestinal wall of the rectum is thin with well‐developed rectal pads. The rectal epithelial cells form a squamous monolayer. A cryptonephric excretory system is located in the hindgut. There are six spiral Malpighian tubules, in which a cellular layer on a basement membrane encloses a lumen. These results will provide the basis for further studies of the structure and function in S. insularis larvae.

Gut Bacteria of Wood-Boring Streltzoviella insularis and Their Involvement in Pinoresinol Degradation of Ash Tree (Fraxinus sp.) Host

“…Previous studies have suggested that detoxification enzymes of S. insularis, such as P450 monooxygenases, are responsible for metabolization of the host tree defensive chemicals . However, in this study, we showed for the first time that gut microbiota play a major role in host tree defense detoxification in S.…”

“…Previous studies have suggested that detoxification enzymes of S. insularis, such as P450 monooxygenases, are responsible for metabolization of the host tree defensive chemicals. 57 However, in this study, we showed for the first time that gut microbiota play a major role in host tree defense detoxification in S. insularis. In the in vivo degradation experiment, we eliminated the gut bacteria of S. insularis by antibiotic treatment to generate larvae that are relatively free of gut microbial symbionts and tested their ability to detoxify pinoresinol compared to nonantibiotic-treated larvae.…”

“…treatments, respectively. Based on the metabolism of coniferyl alcohol, ,, 14 of the total 2608 metabolites were expected to be biologically significant based on previous studies of pinoresinol metabolism − (Table ). Consisted with previously reported pinoresinol degradation pathways, ,,, the gut bacteria of S.…”

Morphological and Structural Observation on the Rectum of Bolua turkiyae Ünal, 1999 (Orthoptera, Tettigoniidae)

“…There is no rectal pad in rectum in some insect species such as Pylaemenes mitratus (Phasmid: Basillidae) [10] and Karenia caelatata (Hemiptera: Cicadidae) [11]. On the contrary, there is found the rectal pad in the rectum of Streltzoviella insularis (Lepidoptera: Cossidae) [12], Cryptotermes brevis (Blattodea, Kalotermitidae), Cryptotermes cavifrons (Blattodea, Kalotermitidae), Coptotermes formosanus (Blattodea, Rhinotermitidae), Neotermes jouteli (Blattodea, Kalotermitidae) [13], Gryllus pennsylvanicus (Orthoptera, Gryllidae) [14], and Poecilimon cervus (Orthoptera, Tettigoniidae) [15] similar to the rectum of B. turkiyae. The presence or not of rectal pads may be related to the insect's diet.…”

Prospecting the insect model, Galleria mellonella, for gut-related pathobiology

“…The differentiation of ISCs is controlled by the secretion of hormones from endocrine cells within the epithelial layer of the midgut (Franzetti et al, 2016). The foregut of larvae contains sclerotized microspines to assist digestion, little to no absorption of nutrients occurs here but serves to start the physical degradation of the food and passage of the bolus into the midgut (Wang et al, 2018).…”