Selective breeding of heat-tolerant black soldier fly (Hermetia illucens) larvae: gut microbial shifts and transcriptional patterns

The black soldier fly larvae (BSFL) have garnered great attention for their potential role in converting organic waste into high-quality insect proteins, providing valuable feed components for animal production and highly enriched organic manure for crop production. However, environmental factors such as high temperatures can compromise their productivity. To address this, we conducted selective breeding of BSFL at 40 °C, and the bred group was improved with higher body weight, survival rates, and substrate reduction after nine generations of breeding. Notably, the gut microbiota of the heat-tolerant colony was highly represented by the bacteria belonging to Proteobacteria, Firmicutes, and Actinobacteria, while the Bacteroidetes phyla were decreased. Transcriptomic analysis revealed that the upregulated genes in 40 °C bred groups were primarily involved in biological processes such as Spliceosome, FoxO signaling pathway, longevity regulating pathways, Drug metabolism, and Xenobiotic metabolism via cytochrome P450. These findings provide a detailed understanding of the molecular mechanisms underlying BSFL's adaptation to heat stress, facilitating future industrial application advancements.