LIU Xue-zhou1,2*, SHI Bao1, LIU Yong-shan1,2, ZHANG Yan-xiang3, GAO Quan-yi3, XU Yong-jiang1, WANG Bin1, JIANG Yan1, SONG Xue-song1,2
1.Qingdao National Laboratory for Marine Science and Technology, Laboratory for Marine Fisheries Science and Food Production Processes, Yellow Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Qingdao 266071, China; 2.College of Fisheries and Life Science, Shanghai Ocean University, Shanghai 201306, China; 3.Dalian Fugu Fishery Company Limited, Dalian 116400, China
Abstract: The changes in gill Na+/K+-ATPase activity, contents of Na+, K+, and Cl- and osmotic pressure were determined in urine, plasma and serum and survival and histological structure of tissues related to osmotic regulation of juvenile yellowtail kingfish Seriolaaureovittata with body weight of 80-120 g held in a salinity of 29 (as control group) directly transformed into water with a salinity of 35, 29, 15, 10, 5 and 0 at water temperature of 22-23 ℃ for 120 h to investigate the effect of abrupt change in salinity on osmotic regulation function of juvenile yellowtail kingfish. It was found that some juvenile yellowtail kingfish was dead in 25 min, and all of the fish dead in 50 min in the fish in the 0 salinity group, without dead in other groups. The activity of gill Na+/K+-ATPase was shown to be decreased gradually with the increase in treatment time elapse in the salinity 5, 10, and 15 groups, significant differences from that in the control group(P<0.05). In salinity 35 group, however, the activity of gill Na+/K+-ATPase was increased gradually and then decreased, remained stable in 96 h, without significant difference between 48 h and 96 h (P>0.05). The change in activity of gill Na+/K+-ATPase showed ‘U ’ shaped distribution in the fish in each salinity group after 72 h exposure or 96 h exposure, according to the different salinities. The concentrations of Na+, K+ and Cl- in urine, plasma and serum were continuously decreased in 6-72 h in salinity 5, 10 and 15 grousp, significant difference from the control group (P<0.05), with the minimum at 96 h, and then remained stable. The concentration of ions was increased in 35 groups with exposure period, with the peak at 120 h. The osmotic pressure in the urine and plasma was significantly decreased with the decrease in salinity and the exposure period in the salinity 5, 10 and 15 groups (P<0.05), significant increase with the increase in salinity and exposure period in the salinity 35 group (P<0.05), stable after 72 h, without significant difference between the salinity groups and the control group at each time point (P<0.05). The activity of Na+/K+-ATPase in gills, contents of Na+, K+, Cl- in urine, plasma and serum and osmotic pressure appeared continually to be decreased with elspase of the increasing salinity in the salinity 5, 10 and 15 groups, most of these indices tending to be stabilized after 96h. In the high salinity (35 salinity group), however, these indices were found to be increased. Electron microscopy showed that the gills were curved at the root, the gill lamellae adhered to the surface with more folds, large amount of secretary mucus substances on skin, and large number of granular substances in the renal epidermis in a 5 salinity group, with less histological damage in the fish in the 35 salinity group. The findings indicate that yellowtail kingfish has a strong ability of osmotic adjustment for salinity variation by changing the content of ions in fish and by regulation of Na+/K+-ATPase activity in gills.
2019, Vol. 34 
