EFFECTS OF LONG-TERM LOW SALINITY EXPOSURE ON IMMUNOLOGICAL AND PHYSIOLOGICAL PARAMETERS OF JUVENILE SHRIMP Litopenaeus vannamei  

The effects of different salinities (1, 10, 15, 25, and 35 g L^-1) on total hemocyte count (THC), phenoloxidase (PO), total phenoloxidase (total PO), and prophenoloxidase (proPO) activities, glucose concentration, plasma protein content, morphometric indexes [condition factor (CF) and hepatosomatic index (HIS)], and growth performance [final weight, specific growth rate (SGR), and survival] of the shrimp Litopenaeus vannamei were determined. At 1, 30, and 63 days of culturing, six shrimp per treatment were selected randomly to determine immunological and physiological characteristics. The performance and morphological characteristics of shrimp exposed to different salinities were not significantly different, except for low survival in salinity of 10 g L^-1. Lower THC, growth, HIS, CF, total PO, and proPO, higher hemolymph glucose concentration, and lower hemolymph protein concentration were also observed in the 10-g L^-1 treatment. High growth and survival in salinity of 1 g L^-1 indicated the capacity of L. vannamei to adapt to low salinity. No significant differences were observed in THC, glucose, and protein concentrations over the varying culture durations (1, 30, and 63 days) or among salinity treatments. The shrimp exposed to a salinity of 25 g L^-1 had slightly higher HIS, THC, and protein concentration in the hemolymph, which agrees with the isosmotic point of shrimp.