Survival, Na+/K+-ATPase and lipid responses to salinity challenge in fed and starved white pacific shrimp (Litopenaeus vannamei) postlarvae

Fed (3-h starved) and 24-h starved 20-day-old postlarvae (P20) were compared to establish the effect of energy reserves on survival rate at 0 ppt and osmoregulatory mechanisms at 10 ppt. The activity of Na+/K+-ATPase was fivefold higher in posterior gills than anterior gills. The activity of Na+/K+-ATPase increased by 63% in both anterior and posterior gills in shrimp subjected to a salinity challenge. No significant increase in carbonic anhydrase activity was observed in P20 exposed to dilute medium. Starvation did not affect these osmoregulatory responses, although starved P20 had a significantly lower survival rate when exposed to dilute medium of 0 ppt. These results indicate that the lower survival rate from a salinity stress test on starved P20 cannot be fully explained by impairment of the osmoregulatory mechanisms. Total lipids (TL) in the hepatopancreas were significantly lower in starved P20, and triacylglycerides (TG) were slightly but not significantly lower in P20 exposed to 10 ppt. In gills, triacylglycerides were significantly higher in P20 exposed to 10 ppt. These results suggest a mobilization of lipids to satisfy the energy demands of the osmoregulatory response or an increase in metabolism as part of a general stress response. (C) 2004 Elsevier B.V All rights reserved.