PROTEIN ACCUMULATION,AMINO ACID PROFILE AND AMINO TRANSFERASE ACTIVITIES OF THE WHITE SHRIMP, LITOPENEA US VANNAMEI, AT DIFFERENT SALINITIES

Shrimp farming in inland saline water has been undertaken in many parts of the world. Particularly, the culture of white shrimp, Litopenaeus vannamei, has becoming a rapid growing industry due to its tolerance to a wide range of salin-ity from 1‰ to 50‰. Although L. vannamei are euryhaline and able to tolerance a wide range of salinity, a salinity change does alter its growth performance and physiological responses. And even the optimal salinity for the growth of white shrimps is controversial, research on L. vannamei at low salinity is still limited. The physiological responses are believed to be es-sential to assess the animal performance at different environmental conditions. Therefore, it is necessary to conduct further investigation on the physiology of L. vannamei at low salinity for inland saline water farming.The objective of this study was to further explore the adaptive mechanisms of white shrimp to different salinities in providing extra energy for osmoregulation at various salinities, and to explore which amino acids are the main osmolytes for L. vannamei. Therefore, shrimps which have been acclimated at 3.0%, 17.0‰ and 32.0‰respectively with four repli-cates for 50 days were used to analyze the soluble protein of different tissues, muscle amino acid profile and contents, Glatamic oxalaeetic transferase (GOT) and Glutamat Pyruvat Transferase (GPT) activities. During the experimental peri-od, the shrimp were fed with a commercial feed containing 40.02% protein, 8.5% crude lipid, 12.0% ash, and 10.2% moisture, and Reeirculation systems were used in the experiment. The results showed that shrimps at 3.0‰ had signifi-cantly higher soluble protein content of hepatopancreases and heamolymph than those at both 17.0‰ and 32.0‰ (p0.05). Low salinity 3.0‰ and high salin-ity 32%0 led to the slight increase of both GOT and GPT activities in muscle though without significant differences (p>0.05) comparing with 17.0‰ treatment. Shrimps at 3.0‰ and 32.0‰ had significant higher levels of total amino acids and total essential amino acids in muscle than those at 17.0‰ (p0.05).All these results indicated that under salinities away from its optimal salinity, the white shrimp ensured themselves to have sufficient amino acids for osmoregulation by accumulating protein in the hepatopancreas and heamolymphs, and accel-erating the amino transfer speed by increasing Glatamic oxalaeetic transferase and Glutamat Pyruvat Transferase activities. Besides, the results also revealed that as one the main five osmolyte amino acids, the amino acid of proline is the main one among these amino acids which play important roles for osmoregulation for L. vannamei.