盐度对日本鳗鲡(Anguilla japonica)渗透压调节的影响

Effect of salinity on osmoregulation of Anguilla japonica

以日本鳗鲡(505.1±35.7)g为实验对象,分别在淡水(盐度0)、盐度10和盐度33条件下处理14 d,在0、1、4、12、24、96 h和14 d时测定其血清渗透压、离子(Na+、K+、Cl-)浓度和鳃Na+/K+-ATP酶活力指标。结果表明:日本鳗鲡血清等渗点为329.1 m Osm·kg-1,其对应盐度为10.48;随着处理时间延长,盐度处理组血清渗透压、Na+和Cl-浓度均呈现先上升后下降的趋势;血清K+浓度受盐度影响较小(P>0.05);盐度10处理组鳃Na+/K+-ATP酶活力于12 h达到最小值(5.40±0.72)μmol·mg-1·h-1,至96 h时恢复至淡水组水平(P>0.05);而盐度33处理组鳃Na+/K+-ATP酶活力则表现为先快速下降,后快速上升,并于24 h达到最大值(13.05±0.62)μmol·mg-1·h-1,约为淡水组的1.5倍(P<0.05)。日本鳗鲡的渗透压调节可初步分为3个阶段:(1)快速升高期,血清渗透压、Na+和Cl-浓度异常升高,鳃Na+/K+-ATP酶活力受到抑制;(2)缓慢升高期,鱼体补偿失水以缓解渗透压升高,血清渗透压、Na+和Cl-浓度表现为缓慢升高,鳃Na+/K+-ATP酶被激活;(3)适应期,鳃Na+/K+-ATP酶活力处于较高水平,血清渗透压、离子浓度基本恢复。

In the present study, the Japanese eels （ 505.1± 35.7 ） g, Anguilla japonica, were reared at salinity 0 （control）, 10, 33 for 14 days respectively. The serum osmolality, ion con- centration and activity of gill Na^＋/K^＋-ATPase were measured at 0, 1, 4, 12, 24, 96 h and 14 d. The result showed that the isosmotic point was estimated as 329.1 mOsm · kg^-1 and corresponded to salinity 10.48. With the increased duration of experiment, serum osmolality and ions （Na^＋, Cl^-） concentration showed a similar fluctuating tendency of a decrease after an initial increase. The serum concentration was less affected by the salinity. The gill Na^＋ /K^＋ -ATPase activity in salinity 10 reached the minimum （5.40±0.72） μmol·mg^-1·h^-1 at 12 h, and then recovered to （7.17±0.85） μmol·mg^-1·h^-1 at 96 h, which was not significantly different from that in the control （P〉0.05）. However, at salinity 33, the gill Na^＋/K^＋-ATPase activity descended acutely, then ascended rapidly and the maximum was observed at 24 h （13.05±0.62） μmol·mg^-1·h^-1 , which was 1.5 times higher than that in the control （P〈0.05）. Therefore, there were three phases in the osmoregulation of Japanese eels in response to salinity change. The first was the rapid increase period, in which serum osmolality and ions （Na^＋ , Cl^- ） concentration increased abrupt- ly, whereas the gill Na^＋/K^＋-ATPase activity was inhibited. The second was the slow increase pe- riod, in which serum osmolality and ions （Na^＋ , Cl^-） increased slowly, and the gill Na^＋/K^＋-AT-Pase activity was activated to compensate the loss of water to alleviate the rise of osmolality. The third was the adaptation period, in which the gill Na^＋/K^＋ATPase activity was in high state, and the active transport ability was enhanced, resulting in gradual recovering of the serum osmolality and ions （ Na^＋, Cl^- ） concentration.