EFFECT OF WATER SALINITY ON TISSUE MINERALISATION IN PENAEUS VANNAMEI (BOONE, 1931)

A 45-days indoor laboratory trial was performed with juveniles of Penaeus vannamei (3.11±0.64 g) to evaluate the effect of salinity on mineral contents in different tissues. Juveniles of P. vannamei were acclimatised to different salinity levels of 3, 10, 20, 30, 40, 50 and 60‰, using sea salt or freshwater at the rate of 2‰ per day from the original salinity. A total of 45 pre-acclimatised shrimps were taken for each treatment with three replications. At the end of the experimental period, shrimps were dissected to remove hepatopancreas, muscle and exoskeleton after collecting haemolymph; which were subjected to mineral analysis by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Calcium deposition was reduced by 55 and 40% in muscle and exoskeleton, respectively, whereas it increased by 142% in hepatopancreas of shrimp reared in 60‰ compared to 20‰ salinity. Magnesium and sodium content increased with increasing salinity in all the tissues except in muscle. Of all the macro elements, phosphorus (7.66 to 9.17 g kg-1) was high in muscle and calcium was predominant in exoskeleton (44.30 to 79.98 g kg-1) while sodium dominated in haemolymph (159.34-327.73 mmol l-1) compared to other elements. Shrimps reared in various salinities did not show significant difference in nutritional value in terms of mineral content in muscle. Results indicated that P. vannamei is a very efficient osmoregulator in low saline environment, in particular at 10 to 30‰ compared to the extreme high saline environment (60‰).