Stress response of Lymantria dispar asiatica (Lepidoptera: Erebidae) larvae and its gut microbiota to manganese ion

To study the effect of manganese exposure on the herbivorous insect Lymantria dispar asiatica, fourth-instar larvae were fed a MnCl 2 -amended diet (LdMn) for 84 h (0.40 mmol MnCl 2 /g diet). Larvae were weighed before and after the diet administration to assess larval gain in mass under manganese exposure. The whole bodies of half of the survivors were ground in liquid nitrogen for measuring enzyme activities and total antioxidant capacity (T-AOC). The intestinal tracts of the remaining survivors were collected and immediately frozen in liquid nitrogen for 16S rDNA sequencing of gut microbiota. Larvae under manganese stress lost significant mass ( p < 0.05). The activities of digestive and antioxidant enzymes and T-AOC, but not trehalase and polyphenol oxidase, were significantly higher after Mn exposure, ( p < 0.05). A Venn diagram illustrated that the gut microbial OTU composition in the larvae also changed. Community pies and correlation heatmaps also showed different relative abundances of gut microbes. In other words, species quantity and relative abundance of gut microbes agreed with PCoA visualization and indicated that the gut microbial community in L. dispar asiatica larvae differed significantly between control and LdMn. Functional classification also suggested that exposure to manganese stress significantly decreased gut microbial coenzyme transport and metabolism in L. dispar asiatica larvae. These results further our understanding about stress response of L. dispar asiatica larvae.