Microcystin-Lr-Induced Changes in Growth Performance, Intestinal Microbiota, and Lipid Metabolism of Black Soldier Fly Larvae (Hermetia illucens)

Biological treatment by black soldier fly larvae (BSFL) has proven to be an effective method for the resource utilization of cyanobacteria, but the effects of microcystin-LR (MC-LR) in cyanobacteria on BSFL growth have not been adequately explored. To evaluate the inhibitory effect and toxic mechanism of MC-LR on BSFL, the growth performance and intestinal microbiota were examined after exposure to 0, 10, 100, and 1000 mu g/kg of MC-LR. The larval weight and survival rate were each significantly inhibited by 21.53% and 21.49% compared with the control group, respectively, after exposure at a concentration of 1000 mu g/kg MC-LR for 16 days. Lipid accumulation, intestinal inflammation, and oxidative stress were observed in three treatment groups, with dose-dependent inflammation ocurring in the intestine. Compared with the control group, superoxide dismutase and catalase activity levels were significantly increased by 74.91% and 49.58%, respectively, which confirmed the occurrence of oxidative stress induced by MC-LR. Furthermore, MC-LR altered the diversity of intestinal microbiota and increased the relative abundance of pathogenic bacteria (e.g., Paenibacillus, Clostridium_sensu_stricto_1, and Lachnoclostridium), which increased the risk of disease in BSFL and contributed to observed metabolic disorders. On the other hand, qRT-PCR analysis further confirmed the occurrence of oxidative stress and the activation of the peroxisome proliferator-activated receptor signaling pathway, resulting in the upregulation of fatty acid synthesis-related genes, ultimately leading to lipid accumulation and apoptosis. These findings provide valuable insights into the ecological risks associated with MC-LR during the process of cyanobacterial resource utilization.