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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]

Parasitoids are important components of the natural enemy guild in the biological control of insect pests. They depend on host resources to complete the development of a specific stage or whole life cycle and thus have evolved towards optimal host exploitation strategies. In the present study, we report a specific survival strategy of a fly parasitoid Exorista sorbillans (Diptera: Tachinidae), which is a potential biological control agent for agricultural pests and a pest in sericulture. We found that the expression levels of nitric oxide synthase (NOS) and nitric oxide (NO) production in host Bombyx mori (Lepidoptera: Bombycidae) were increased after E. sorbillans infection. Reducing NOS expression and NO production with an NOS inhibitor (NG‐nitro‐L‐arginine methyl ester hydrochloride) in infected B. mori significantly impeded the growth of E. sorbillans larvae. Moreover, the biosynthesis of 20‐hydroxyecdysone (20E) in infected hosts was elevated with increasing NO production, and inhibiting NOS expression lowered 20E biosynthesis. More importantly, induced NO synthesis was required to eliminate intracellular bacterial pathogens that presumably competed for shared host resources. Inhibiting NOS expression down‐regulated the transcription of antimicrobial peptide genes and increased the number of bacteria in parasitized hosts. Collectively, this study revealed a new perspective on the role of NO in host–parasitoid interactions and a novel mechanism for parasitoid regulation of host physiology to support its development. [ABSTRACT FROM AUTHOR]

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 intensive application of chlorantraniliprole (CAP) leaves residues in the environment, posing a potential threat to non‐target organisms. In the present study, we investigated the adverse effects of sublethal CAP exposure on Bombyx mori. Sublethal CAP (0.02 mg/L) was shown to induce the release of intracellular Ca2+ in BmN cells. Meanwhile, Ca2+‐dependent genes were induced in the midgut at 72 h after CAP (0.01 mg/L) exposure, and damaged mitochondria, autophagosomes, nuclear membrane rupture and condensed chromatin were observed. Moreover, the key genes in the oxidative phosphorylation pathway were significantly down‐regulated. The transcript levels of autophagy‐related genes ATG6 and ATG8 were significantly up‐regulated, and the protein levels of LC3‐II and ATG7 were significantly increased by 3.72‐ and 3.33‐fold, respectively. Additionally, the transcript levels of the upstream genes in the apoptosis pathway (calpain and Apaf‐1) were significantly up‐regulated, the protein levels of the downstream gene caspase 3 and its cleaved form were significantly up‐regulated by 1.97‐ and 4.55‐fold, respectively, consistent with the elevated caspase 3 activity at 72 h. Collectively, these findings demonstrate that intracellular Ca2+ release induced by sublethal CAP inhibits oxidative phosphorylation pathway, which causes mitochondrial dysfunction, leading to autophagy and apoptosis in the midgut of B. mori. [ABSTRACT FROM AUTHOR]

As a new type of biologically compatible material, TiO2 NPs are widely used in the industry as additives, drug carriers, and components of skin care products. Due to their wide use, residual TiO2 NPs in the environment are a safety concern that has attracted extensive attention. In this study, the ovarian cell line BmN of the model organism Bombyx mori was used to reveal the damaging effects of TiO2 NPs exposure. The results demonstrated that TiO2 NPs exhibited a dose-dependent effect on the relative cell viability, with significant toxic effects being observed above 20 mg/L. Oxidative damage analysis showed that ROS accumulated significantly in BmN cells after exposure to TiO2 NPs (P ≤ 0.05) and induced DNA damage. Further analysis revealed that the transcriptional levels of key superoxide dismutase genes (SOD) decreased significantly, while the transcriptions of key genes of the MAPK/NF-κB signaling pathway (P38, MEK, ERK and REL) and the downstream inflammatory factor genes (IL6 and TNFSF5) were all significantly up-regulated (P ≤ 0.05). Overall, our results indicate that exposure to TiO2 NPs leads to reduced transcription of antioxidant genes, accumulation of peroxides, and inflammation. These findings provide valuable data for the safety evaluation of environmental residues of TiO2 NPs. [ABSTRACT FROM AUTHOR]