低盐水体Na^(+)/K^(+)对凡纳滨对虾生长、体成分与肝胰腺、鳃组织结构的影响

Effects of Na^(+)/K^(+)ratio on growth,body composition,hepatopancreas and gill microsturucture of Litopenaeus vannamei reared in low-salinity environment

缺钾在内陆低盐度盐碱水中经常发生,为探究低盐水体中不同钾缺乏程度对凡纳滨对虾生长、存活、体成分以及鳃和肝胰腺组织结构的影响,实验参照海水离子组成配置盐度为2的低盐度水体,在Na^(+)/K^(+)(mg/mg)比值为27、47、67、87、107 (分别记为A、B、C、D、E组)的条件下,对体重为(1.04±0.23) g的凡纳滨对虾幼虾开展了为期60 d的养殖实验。结果显示,E组对虾的存活率为44.64%±20.95%,显著低于A、B、D三组;E组体重为(4.86±0.66) g,显著低于其他4组;A~D组之间的湿重、增重率、特定生长率差异不显著,但均大于E组且差异显著;在饲料系数上,E组最高并与A、D组差异显著。在体成分上,各组全虾钾含量、灰分含量差异不显著,E组的水分含量高于其他组,并与A、B组差异显著;E组粗蛋白含量最低,且与B组差异显著。E组对虾鳃组织角质层明显受损,红细胞数量减少,空泡增多,肝胰腺B细胞及其内部转运泡体积增大,肝小管结构受损。研究表明,低盐条件下严重缺钾引起了对虾鳃和肝胰腺损伤,降低了对虾的存活率和生长率;水体缺钾在前期即可对对虾的生长产生明显影响,而对存活的影响随养殖时间的增加而增大。实验结果有助于为内陆低盐度盐碱水养殖凡纳滨对虾提供理论依据。

Potassium deficiency often occurs in inland low-salinity saline waters,which is a major challenge to fishery utilization of such resources.In order to explore the effects of potassium deficiency in low-salinity water on the growth,survival,body composition,gill and hepatopancreas tissue structure of Litopenaeus vannamei,a 60-day growth experiment was set up using diluted artificial seawater at salinity of 2.Juvenile shrimps with body weight of(1.04±0.23)g were cultured under the conditions of Na^(+)/K^(+)(mg/mg)ratio of 27,47,67,87 and 107(group A,B,C,D and E,respectively).The results showed that the survival rate of group E was 44.64%±20.95%,which was significantly lower than that of groups A,B and D;body weight of group E was(4.86±0.66)g,which was significantly lower than that of the other four groups.There were no significant differences in wet weight,weight gain and specific growth rate between groups A and D,but they were all higher than those in group E.The feed coefficient in group E was the highest and significantly different from that in groups A and D.In terms of body composition,there were no significant differences in potassium and ash content of whole body between all groups,and water content in group E was higher than that in other groups,and significantly different from that in groups A and B.The crude protein content in group E was the lowest,and was significantly different from that in group B.In group E,the shrimp gill cuticle was significantly damaged,the number of red blood cells decreased,vacuoles increased,the volume of hepatopancreas B cells and their internal transport vesicles increased,and the structure of hepatic tubules was damaged.The results indicated that severe potassium deficiency under low salin-ity conditions causes damage to the gills and hepatopancreas of the shrimp,which also reduces its survival and growth.Potassium deficiency in water body has a significant effect on the growth of L.vannamei even in the early stage,while its influence on the survival increasesh along the culture period,which means supplementation of potassium is necessarily at the beginning of farming.These findings would help to provide theoretical and prac-tical support for the aquaculture exploitation of inland low salinity waters.