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The survival of species is negatively impacted by the increased frequency and intensity of high‐temperature episodes caused by increased global warming. Thermal tolerance can influence population size and the geographic distribution of species, which translates into species‐wide responses to climate and affects interactions between communities of species. The silkworm, Bombyx mori (L.) (Lepidoptera: Bombycidae), is an ectotherm and an internationally recognized model insect for studying sensitivity to the environment. In the present study, we investigated the effects of different diets on the thermal tolerance of silkworm. As such, it was identified that silkworms reared on an artificial diet in instars I–III and mulberry leaves in instar IV (referred as the AM group) exhibited faster weight gain and higher antioxidant enzyme activity at 35 °C, whereas silkworms reared only on mulberry leaves (referred as the ML group) exhibited upregulated transcript levels of key genes regulating antioxidant enzyme signaling pathways including Akt, CncC, and keap1, significantly increased reactive oxygen species (ROS) levels, and severely impaired midgut activity at 35 °C. Thus, the AM group presented stronger thermal tolerance. These findings suggest that diet can affect the thermal tolerance of silkworm. This research improved our understanding of the molecular, biochemical, and physiological changes caused by thermal stress and laid the groundwork for future research regarding the mechanism underlying thermal tolerance. Furthermore, this study provides an important reference for the conservation of biodiversity in the context of global warming. [ABSTRACT FROM AUTHOR]

The Duox-ROS defense system plays an important role in insect intestinal immunity. To investigate the role of intestinal microbiota in Duox-ROS regulation herein, 16S rRNA sequencing technology was utilized to compare the characteristics of bacterial populations in the midgut of silkworm after different time-periods of treatment with three feeding methods: 1–4 instars artificial diet (AD), 1–4 instars mulberry leaf (ML) and 1–3 instars artificial diet + 4 instar mulberry leaf (TM). The results revealed simple intestinal microbiota in the AD group whilst microbiota were abundant and variable in the ML and TM silkworms. By analyzing the relationship among intestinal pH, reactive oxygen species (ROS) content and microorganism composition, it was identified that an acidic intestinal environment inhibited the growth of intestinal microbiota of silkworms, observed concurrently with low ROS content and a high activity of antioxidant enzymes (SOD, TPX, CAT). Gene expression associated with the Duox-ROS defense system was detected using RT-qPCR and identified to be low in the AD group and significantly higher in the TM group of silkworms. This study provides a new reference for the future improvement of the artificial diet feeding of silkworm and a systematic indicator for the further study of the relationship between changes in the intestinal environment and intestinal microbiota balance caused by dietary alterations. [ABSTRACT FROM AUTHOR]

Florfenicol (FF) is a new antibiotic commonly used in sericulture. This study aimed to examine the effects of low (LC: 0.06 g/L), medium (MC: 0.12 g/L), and high (HC: 1.2 g/L) concentrations of FF on the midgut physiological functions of the silkworm, Bombyx mori (L.) (Lepidoptera: Bombycidae). The results showed that the body weight and the whole cocoon weight of silkworms decreased and the development duration of the fifth instar was prolonged in the HC group. The structure of intestinal microbiota of silkworm larvae was changed by high FF exposure. Specifically, the abundance of conditional pathogens (Curtobacterium, Sanguibater, etc.) was significantly increased, whereas the abundance of Pseudomonas and Pedobacter was decreased significantly. Additionally, the intestinal reactive oxygen species level at 72 h was significantly elevated, and the muscle layer had become loose, together with the appearance of gut goblet cell atrophy. We observed that the increase in Lactobacillus abundance led to a reduction in intestinal fluid pH, resulting in decreased α‐amylase and protease activities, whereas lipase activity exhibited an elevation. The results demonstrated that the accumulation of peroxides induced by exposure to 1.2 g/L FF caused intestinal damage, and the decrease in pH resulting from alterations in microbial composition and structure affected digestive enzyme activity, collectively leading to physiological impairment of the silkworm midgut. These findings provide a valuable reference for the safe use of FF in sericulture. [ABSTRACT FROM AUTHOR]

Chlorantraniliprole (CAP) is widely used in pest control, and its environmental residues affect the disease resistance of non-target insect silkworms. Studies have demonstrated that changes in gut microbial communities of insects are associated with susceptibility to pathogens. In the present study, we examined the effects of CAP exposure on the immune system and gut microbial community structure of silkworms. The results showed that after 96 h of exposure to low-concentration CAP, the peritrophic matrix (PM) of silkworm larvae was disrupted, and pathogenic bacteria invaded hemolymph. The trehalase activity in the midgut was significantly decreased, while the activities of chitinase, β- N -acetylglucosaminidase, and chitin deacetylase were increased considerably, resulting in decreased chitin content in PM. In addition, exposure to CAP reduced the expressions of key genes in the Toll, IMD, and JAK/STAT pathways, ultimately leading to the downregulation of antimicrobial peptides (AMPs) genes and alterations in the structure of the gut microbial community. Therefore, after infection with the conditional pathogen Enterobacter cloacae (E. cloacae), CAP-exposed individuals exhibited significantly lower body weight and higher mortality. These findings showed that exposure to low-concentration CAP impacted the biological defense system of silkworms, changed the gut microbial community structure, and increased silkworms' susceptibility to bacterial diseases. Collectively, these findings provided a new perspective for the safety evaluation of low-concentration CAP exposure in sericulture. [Display omitted] • Low concentrations of chlorantraniliprole destroyed the peritrophic matrix of silkworms. • Low concentrations of chlorantraniliprole dysregulated intestinal immune signaling pathways. • Chlorantraniliprole perturbed intestinal microbial homeostasis and changed microbial community. • Chlorantraniliprole reduced the resistance of silkworms to harmful microbes. [ABSTRACT FROM AUTHOR]