Salinity stress test and its relation to future performance and different physiological responses in shrimp postlarvae

This review evaluates the use of the salinity stress test (SST) as an index of postlarvae (PL) quality, either at the end of experimental treatments or to predict performance during stocking and growout. The SST is easy to apply and does not require specialized equipment, hence its popularity. However, predictive value of the test seems to be limited to short-term performance during future culture. To determine to what extent SST depends on osmoregulation, the mechanisms in crustaceans are briefly reviewed, with particular emphasis on studies related to SST in PL penaeid shrimp. Two main physiological features of osmoregulation, active ion transport through the Na+/K+-ATPase pump and fatty acid composition of membranes affecting permeability to water and ions, cannot fully explain differential survival to an SST. This observation is derived from different experimental models, which include nutritional conditions or normal (genetic) variation. Other traits of the overall physiological condition appear to be involved and are not related to physiological regulation but rather are a result of a possible increased tolerance capacity.