Microbiome Dynamics in Samia cynthia ricini: Impact of Growth Stage and Dietary Variations

This study investigates the gut microbiome of Samia cynthia ricini, a domesticated silkworm species in Assam and Northeast India that is known for its Eri-silk production. Samples were collected at various growth stages and under different dietary conditions, generating 6341 features. The 5th instar larvae of the Eri-fed group exhibited the highest feature count, while moths from the same group had the lowest. The microbiome was characterized by 11 dominant taxa, mainly Proteobacteria, Firmicutes, Actinobacteria, and Bacteroidetes. Notable differences were observed between larval and moth samples, with adult moths—particularly Eri-fed females—having a higher abundance of Bacteroidetes. Specific taxa such as Oscillospira, Sutterella, Succinivibrionaceae, and Prevotella were more abundant in adult moths. Eri-fed samples exhibited greater microbiome diversity, while Kesseru-fed samples were rich in Bifidobacterium. Interaction networks revealed unique species correlations in moths, including Clostridiales, Firmicutes, Gallibacterium, and Lachnospiraceae. Functional analysis highlighted diet-related differences, whereby Kesseru-fed samples showed more carbohydrate metabolism pathways, while larval microbiomes had distinct pathways for aromatic compound degradation and detoxification. Moth samples exhibited increased biosynthesis pathways, protein absorption, RNA transport, and immunogenic functions. This research enhances the understanding of microbiome dynamics in silkworms, offering insights for improved growth conditions and pest management strategies for this economically and ecologically significant species.