Abstract: Owing to their high tolerance to a wide range of salinity, white shrimp (Litopenaeus vannamei) has been generally recognized as an excellent candidate for inland culture. Recently, inland farming of L. vannamei has become a growing industry in many regions of the world. Therefore, the effects of water salinity on the survival and development of L. vannamei has attracted great research interest at present. However, according to previous studies, the salinity adaptability of different families of L. vannamei were found to vary significantly and the most optimal salinity for the culture of L. vannamei is still debatable, which pose a challenge for the selection of seed juvenile for inland culture. It has been reported that the different salinity adaptability of different families of L. vannamei may be due to different genetic backgrounds, and the underneath mechanism remains unknown. This study compared the growth traits (specific growth rate and survival rate) under different salinity conditions (5‰, 20‰ and 30‰) among 30 families of L. vannamei. Consistent with previous studies, our results demonstrated that the specific growth rates of shrimps were significant different among different families after 30 days exposure to different salinity conditions. Four L. vannamei families with two highest (family 6016 and 6022) and two poorest salinity adaptability (family 6039 and 6040) were chosen based on specific growth rates and survival rates of 30 L. vannamei families for further investigation. Plsama cortisol concentration has long been generally used as an important index for the evaluation of environmental adaptive capacity of aquatic organisms including shrimps. Therefore, in this study, the plsama cortisol concentration of shrimps from different families were measured after 30 days exposure to different salinity conditions by using commercial ELISA kit. The plsama cortisol concentrations of shrimps from family 6039 and 6040 at salinity of 5‰ were significantly (P<0.05) higher than those from family 6016 and 6022, which indicated a stress response of these shrimps at a water salinity of 5‰ even after 30 days accommodation. This result suggested that these shrimps from family 6039 and 6040 may be inadaptable to the lower water salinity conditions, which may therefore lead to the inhibited growth and survival rates of shrimps of these families as observed in the present study. According to previous studies, Na⁺/K⁺-ATPase and Ca²⁺-ATPase are key enzymes for the regulation of osmotic pressure involved in the active transport of ions including Na⁺, K⁺ and Ca²⁺ in the animal cells. Furthermore, the adaptation of aquatic animals, especially marine animals, to a low salinity environment has been reported to be mediated by these enzymes. As a result, in order to explore the physiological mechanism of the varied adaptation to an altered salinity among these L. vannamei families, the enzymatic activities of Na⁺/K⁺-ATPase and Ca²⁺-ATPase in the shrimp gills from different families after 30 days exposure under different salinity conditions were examined by using ATPase activity assay kit in the present study. Results obtained found that both Na⁺/K⁺-ATPase and Ca²⁺-ATPase were significant lower in L. vannamei family 6039 and 6040 compared to that of family 6016 and 6022, suggested the hampered ability for osmotic pressure maintenance of shrimps from family 6039 and 6040. Since the driving of active transport of osmoregulatory related ions by Na⁺/K⁺-ATPase and Ca²⁺-ATPase is a process requiring energy source from ATP, the metabolism as well as the ATP contents and ATP synthase activities in the muscle of shrimps raised under different salinity conditions after 30 days exposure were also analyzed among different families. In the present study, the respiration rates and ammonium excretion rates of shrimps from all families were significantly (P<0.05) altered with the declined water salinity. However, compared to these shrimps from family 6016 and 6022, the families with poor salinity adaptability (family 6039 and 6040) showed a significantly (P<0.05) lower metabolic rates at all water salinity conditions. Similarly, the ATP contents and ATP synthase (pyruvate kinase) activities were also significantly (P<0.05) lower in the muscle of shrimps from these families (family 6039 and 6040) after 30 days exposure, indicated a constrained energy supply under low water salinity conditions. Based on the data obtained in this study, the suppressed Na⁺/K⁺-ATPase and Ca²⁺-ATPase in the gills of shrimps with poor salinity adaptability can be resulted from their energy shortage for osmoregulatory under low water salinity levels. In conclusion, our study demonstrated that the different salinity adaptability among different shrimp families may be due to their differences in metabolism rate, ion transportation, and energy synthesis. In addition, this study will contribute to the efficient production of seed juvenile for inland culture of L. vannamei.