Diversity Characteristics and Composition of Gut Microbiota in Antheraea pernyi (Lepidoptera: Saturniidae) Larvae Across Different Instars

<i>Antheraea pernyi</i> (Lepidoptera: Saturniidae) is an economically important silk-producing insect, whose gut microbiota play a crucial role in growth, development, and nutrient metabolism. This study focused on the entire larval developmental stages of <i>A. pernyi.</i> Using the Illumina MiSeq high-throughput sequencing platform, we performed 16S rRNA gene amplicon sequencing on the gut microbiota of laboratory-reared <i>A. pernyi</i> larvae, analyzing in detail the composition and diversity characteristics of the gut microbial communities across all five instars (1st to 5th instar). Additionally, functional predictions were conducted to explore the potential roles of these microbiota during larvae development. The study revealed that the core gut microbiota of <i>A. pernyi</i> larvae primarily consisted of Actinomycetota (39.78%), Cyanobacteriota (32.46%), Bacillota (18.08%), and Pseudomonadota (9.02%). Among these, Actinomycetota dominated in the 1st to 4th-instar larvae, while Cyanobacteriota became the predominant phylum in the 5th instar. Linear discriminant analysis effect size identified statistically significant biomarkers across different instar larvae of <i>A. pernyi.</i> Alpha diversity analysis showed that gut microbiota diversity initially increased and then decreased with larval development, peaking in the 3rd instar, and reaching its lowest level in the 5th instar. Principal coordinate analysis (PCoA) of beta diversity indicated that the gut microbiota structures of the 1st to 4th instars were similar but significantly differed from that of the 5th instar. Functional prediction analysis based on the KEGG database revealed that Carbohydrate metabolism and Amino acid metabolism-related genes were significantly lower in the 5th instar compared to other instars, while Energy metabolism and Cofactor and vitamin metabolism-related genes were significantly higher. This study offers valuable insights for the development of gut microbial resources in Lepidoptera insects.