EFFECT OF Vibrio harveyi ON IMMUNE SYSTEM OF SHRIMP Litopenaeus vannamei CULTURED IN BIOFLOC
In recent years, different studies about nutrition, reproduction, breeding and environmental improvement have been made to improve shrimp farming in places where this activity is done. An alternative has been the use of biofloc technology, which offers to decrease disease risk in shrimp farming. However, the study of its effect on immune system in shrimps is still scarce.
The immune response in Litopenaeus vannamei infected experimentally with Vibrio harveyi strain CAIM1792 and cultured previously in biofloc system was evaluated. The experimental infection was made using a density of 108 CFU mL-1 (INFECTED treatment). It was a CONTROL treatment inoculated with sterile saline solution. Shrimps in both treatments were inoculated in the third abdominal segment in a dosage of 100 µL. Three replicates were using for each treatment. During four hours, shrimps were maintained under observation until signs were observed related with Bright-Red Syndrome caused by the strain. It was determined total soluble protein (TSP), phenoloxidase (PO), hemocyanin (Hc) and superoxide dismutase (SOD).
After four hours of experimental infection, shrimps in INFECTED treatment registered a high concentration in TSP and SOD. However, there were no significant differences between treatments (Table 1). PO values were lower than the CONTROL (Table 1), due to the rapid effect of bacteria in shrimps, possibly it not allowed reflect the effect of infection on this parameter. Significant differences between treatments were obtained in Hc determination (Table 1), having the highest concentration in INFECTED treatment, which may reflect the immune response to bacterial challenge, so Hc synthesis increased in order to carry more oxygen and to generate an immune response due to infection.