Key gut bacterial taxa and their correlative relationships with host genes during Musca domestica aggregation.

Aggregation enhances survival and reproduction by regulating body coloration, physiology, and immunity. The housefly (Musca domestica) is a notable sanitary pest that exhibits group-breeding behavior during its larval stage, which promotes its growth and development. However, the mechanisms underlying how high larval density regulates growth remain unclear. Previous studies have shown that gut bacteria are important regulators of larval growth and development. To further investigate this, the present study aimed to assess the impact of group rearing on both the gut microbiota and host gene expression in housefly larvae. The results showed that the relative abundance of the gut bacterial genera Enterococcus, Myroides, and Serratia significantly decreased in aggregated larvae compared with single larvae, and the relative abundance decreased as population density increased. Transcriptome analysis revealed that differentially expressed genes were significantly enriched in the lysosome pathway, wherein most genes were aspartic protease genes. The correlation network between gut bacteria and genes demonstrated that aspartic protease genes were closely correlated with changes in the intestinal bacteria. This study identifies intestinal bacterial genera and host genes influenced by population density, lays the foundation for further research on the mechanism underlying that group rearing improves larval growth, and is also expected to offer novel perspectives for pest control through the regulation of population density.