Assessing the impact of chemoautotrophic and heterotrophic biofloc cultivation systems on the immunity and intestinal bacteriome of shrimp

The use of measures to prevent disease and enhance immune competence in shrimp is essential to ensure the sustainability of shrimp aquaculture. We assessed here differences in the immunological status of juvenile Litopenaeus vannamei reared in a mature chemoautotrophic biofloc system (BFT.C) compared to a less stable heterotrophic biofloc system (BFT.H). After 72 days of culture, we examined different standard hemato-immunological parameters (hemograms, phenoloxidase activity, total serum protein concentration, and hemolymph agglutination capacity), the expression of 50 immune-related genes in the midgut, and the transcriptional 16S rRNA levels of the predominant bacterial groups associated with the shrimp gut. Overall, BFT.C demonstrated greater environmental stability than BFT.H, leading to enhanced immunocompetence in the animals. Biofloc-reared shrimp showed enhanced Vibrio agglutination, indicating a superior ability to identify and immobilize bacterial invaders in the hemolymph. Besides, four genes involved in antimicrobial and antiviral defenses (Litvan ALF-A, Lvan-Stylicin1, LvPPAE2, and LvDicer1) showed to be differentially transcribed at basal levels in the midgut of shrimp from both systems of biofloc maturation. Finally, the 16S rRNA transcriptional profiling revealed a greater abundance and viability of Actinobacteria and Firmicutes in the midgut from shrimp reared in BFT.C and BFT.H, respectively. In conclusion, our study evidenced that the biofloc maturation system impacts both hemolymph- and intestine-based immunities of shrimp as well as their midgut bacterial communities. These findings may help to understand how the environment, shrimp immunity, and the bacterial microbiome interact to prevent disease in shrimp farming.