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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]

Silkworm (Bombyx mori) is an economically important insect. However, the survival of silkworms has been significantly affected by the assault of chemical pesticides on mulberry trees through aerial application and water currents. Phoxim is a broad-spectrum organophosphorus insecticide widely used in China. Currently, very little is known about the non-neuronal effects of sublethal exposure to phoxim. The purpose of this study was to investigate the non-neuronal effects of sublethal phoxim exposure in the silkworm midgut, with a focus on nutrient metabolism. After phoxim treatment, lipase activity in the silkworm was shown to be up-regulated at 24 h before a decreasing trend was seen. Meanwhile, α-amylase activity showed the opposite trend. The expression levels of mitochondrial respiratory chain-related genes were all up-regulated at 24 h before falling continuously. To ensure that the effects of phoxim on nutrient metabolism were not simply a consequence of a decrease in mulberry consumption, the silkworms were treated with a reduced-food diet before the digestive enzyme activities and the transcription levels of mitochondrial respiratory chain-related genes were analyzed. Our results showed that the patterns in the reduced-diet and phoxim-exposed silkworm were markedly different, suggesting the alterations in the phoxim-exposed silkworm cannot readily be explained by nutrient deprivation Unlabelled Image • Phoxim exposure alters the mRNA levels of glucose and lipid metabolism-related genes. • Lipase activity showed the opposite trend to α-amylase activity after exposure. • The patterns in the reduced-diet and phoxim-exposed silkworm were markedly different. [ABSTRACT FROM AUTHOR]