Immune response of the Pacific white shrimp,Litopenaeus vannamei,previously reared in biofloc and after an infection assay with Vibrio harveyi

The effectiveness of the immune defense of Litopenaeus vannamei previously reared in biofloc or in a traditional clear seawater rearing system was assessed after a bacterial challenge with a pathogenic strain of Vibrio harveyi. The changes caused by its previous rearing system condition or the challenge were assessed in terms of metabolites (glucose, cholesterol, acylglycerides, protein), hemocyanin, the antioxidant defense system (superoxide dismutase, and catalase), and gene expression related to immune response (superoxide dismutase, alpha2 macroglobulin, prophenoloxidase, hemocyanin, and penaeidin‐3a). The biofloc rearing system was associated with a significant increase in protein, the antioxidant defense system, and the superoxide dismutase, alpha2 macroglobulin, and prophenoloxidase genes. For shrimp previously reared in biofloc, a positive interaction with the presence or absence (control) of V. harveyi significantly affected the hemocyanin concentration, and the interaction between the two rearing systems in shrimp challenged with the bacteria produced a higher transcription of the hemocyanin gene. Likewise, biofloc and clear seawater maintained a higher transcription of prophenoloxidase gene after the bacterial challenge. In the absence of the bacteria, shrimp of the biofloc group produced a higher transcription of the penaeidin‐3a gene. V. harveyi caused hepatopancreatic lesions and mortalities only in shrimp previously reared in clear seawater. These results suggest that biofloc helps to prevent the development of disease by improving the shrimp immune response.