Does the heterotrophic system influence the cellular immune response of Litopenaeus vannamei shrimp? In vitro phagocytosis indices and superoxide anion production comparisons

Aquaculture production has increased in the last decades, with crustacean production contributing with 9.8% of the total production. However, fisheries and aquaculture sectors present several challenges, such as fish stocks fished beyond biological sustainability, animal diseases, biosecurity, and environmental impact. It is important to improve shrimp production with healthy animals, avoiding environmental impacts, e.g. with the use of heterotrophic rearing system. It is known that the heterotrophic system can stimulate the activation of immune genes, but how it affects the shrimp immune system is unknown. To assess if a heterotrophic system influences the cellular immune response in shrimp, Litopenaeus vannamei shrimp were reared in heterotrophic and clear water systems. Cellular immune response parameters such as total and differential hemocyte counts, phagocytosis indices and the production of the superoxide anion were evaluated after 60, 120 and 180 days. After 60 days, total haemocyte counts were higher in shrimps reared in the clear water system, while after 120 days it was higher in shrimps reared in the heterotrophic system. No significant difference was observed after 180 days. Hyaline, granular and semi-granular cells showed similar behavior, peaking after 120 days in the heterotrophic system. By the 60th day, phagocytic capacity was higher in the heterotrophic system, while no differences were found for the 120th and 180th day. No differences were detected concerning the phagocytic index or superoxide anion production. The heterotrophic system can affect total and differential shrimp haemocyte counts and phagocytic capacity, depending on the period of time they were maintained in this system. However, the phagocytic index and superoxide anion production are not affected by the heterotrophic system at the time points evaluated herein.