A systematic meta-analysis reveals enrichment of Actinobacteria and Firmicutes in the fish gut in response to black soldier fly (Hermetica illucens) meal-based diets

Replacement of fishmeal (FM) from aquafeed has gained tremendous attention over the past 20 years due to environmental and ecological ill-impacts of large-scale capture of wild fishes. Insects, black soldier fly (BSF) possess balanced nutritional properties, hence, considered as an ideal candidate for the replacement of FM. A number of studies have been performed on the effects of BSF as a fishmeal alternative on the gut microbiota of aquatic animals using high throughput sequencing (HTS). However, due to the inconsistency in the success of BSF inclusions, a systematic meta-analysis approach was imperative to conclude the usefulness of BSF inclusion in aquafeed. In this context, the present study systematically analysed the HTS data obtained from gut microbiota of BSF, and rainbow trout (RT) fed BSF from various life cycles with different formulations. Results revealed that Actinobacteria and Firmicutes were most abundant in the gut of BSF and fish fed BSF diets while Proteobacteria was the dominant bacteria in the fish gut fed FM. The augmentation of Actinobacteria and Firmicutes in the fish gut was mainly due to higher abundance of Actinomyces, Bacillus, Lactobacillus and Enterococcus at the genus level. More diversified gut microbiota was observed in fish fed larvae and pre-pupae BSF, while defatted BSF was linked to a specific group of bacteria. Feeding BSF was shown to reduce the core microbiota of rainbow trout by increasing Firmicutes. Overall, the findings of this study could be used as future references for fish and shellfish nutrition, specifically in formulating aquafeed with BSF incorporation.