Physiological changes in the hemolymph of juvenile shrimp Litopenaeus vannamei to sublethal nitrite and nitrate stress in low-salinity waters.

Abstract Juveniles of the shrimp Litopenaeus vannamei (3.3 ± 0.4 g) were exposed separately to nitrite (0.0, 1.1, 2.6, and 5.3 mg/L nitrogen as nitrite [NO2−-N]) and nitrate (0, 90, 225 and 400 mg/L nitrogen as nitrate [NO3−-N]) concentrations equivalent to 0, 10, 25, and 50% of the LC50-96 h value of NO2−-N and NO3−-N in low salinity water (3 g/L). Shrimps responded to nitrite and nitrate according to changes in oxyhemocyanin, glucose, lactate and ion levels in the hemolymph after 6, 12, 24, and 48 h of exposure. Oxyhemocyanin levels decreased with increasing nitrite and nitrate levels and were higher at 50% exposure to the contaminants. Compared to the control, glucose and lactate increased significantly at 50% exposure to nitrite and nitrate, particularly at 12 and 24 h. Na+ in the hemolymph changed with nitrite and nitrate, while K+ only changed ˜with nitrite.