不同盐度对四指马鲅幼鱼存活及鳃组织形态变化的影响

The survival and structural changes in gill of juvenile Eleutheronema tetradactylum under different salinities

  • 摘要: 【目的】探究不同盐度对四指马鲅(Eleutheronema tetradactylum)幼鱼存活与鳃组织结构变化的影响,为四指马鲅苗种生产提供有效的技术支持和理论参考。【方法】试验设0、5‰、10‰(对照)、15‰和20‰等5个盐度组,将暂养于盐度为10‰水体中的四指马鲅幼鱼直接放入其他盐度水体中,试验第15 d时进行活体鳃组织取样,采用组织学方法对不同盐度条件下四指马鲅幼鱼的鳃组织结构进行研究。【结果】盐度为0时,四指马鲅幼鱼在12 h之内全部死亡,5‰盐度组幼鱼死亡率成为6.6%,10‰对照组幼鱼无死亡,15‰和20‰盐度组幼鱼死亡率分别为33.3%和60.0%,表明与高盐环境相比,四指马鲅幼鱼更能适应低盐环境,但不能在急性淡水胁迫条件下存活。显微结构观察结果显示,10‰盐度条件下,四指马鲅幼鱼的鳃小片排列紧密,线粒体丰富细胞主要分布在鳃小片基部。随着盐度增加,鳃小片的长度和间距减小,而鳃小片宽度增加。其中,5‰盐度条件下鳃小片的长度、宽度和间距分别为45.19±3.18μm、5.32±1.02μm和17.65±1.43μm,20‰盐度条件下鳃小片的长度、宽度和间距分别为36.67±3.81μm、8.78±2.22μm和11.56±3.81μm,差异均达显著水平(P<0.05)。20‰盐度条件下,鳃小片的远端可观察到线粒体丰富细胞,扁平上皮细胞出现一定程度的脱落或分离现象。扫描电镜观察结果显示,线粒体丰富细胞的顶膜结构分为Ⅰ型(顶膜向内凹陷)和Ⅱ型(顶膜向外凸起)2种类型。5‰盐度条件下,线粒体丰富细胞出现2种类型,主要以Ⅱ型为主,顶膜开口较大,表面有大量微绒毛,扁平上皮细胞表面有隆起的微嵴,形成指纹样回路;10‰盐度条件下,出现Ⅰ型线粒体丰富细胞,扁平上皮细胞表面微嵴形态不规则,细胞间的界限不明显;15‰和20‰盐度条件下,均以Ⅰ型结构为主,且随着盐度增加,顶膜加深,线粒体丰富细胞数量增多,扁平上皮细胞表面微嵴隆起幅度小,指纹样的回路不明显。【结论】当水体渗透压改变时,四指马鲅幼鱼存活率及鳃小片上细胞的数量分布和形态均发生显著变化,鳃组织结构的变化与其所处的环境盐度条件有关。

     

    Abstract: 【Objective】In order to explore the characteristics of the survival and gill histological structure of Eleutheronema tetradactylum juveniles cultured at different salinities, to provide effective technical support and theoretical reference for the production of E. tetradactylum.【Method】Five salinity groups of 0, 5‰, 10‰(control), 15‰ and 20‰were set up in the experiment. The juvenile E. tetradactylum temporarily raised in 10‰ salinity water was directly put into other salinity water bodies. The living gill tissue was sampled on the 15 thday of the experiment. The histological structure of gill of E. tetradactylum juveniles under different salinities were observed by using the histological methods.【Result】Under 0 salinity condition, E. tetradactylum juveniles all died within 12 h, at 5‰ salinity condition, the mortality rate was 6.6%, no death in the control group, the mortality rates of 15‰ and 20‰ salinity were 33.3% and 60.0% respectively.Compared with the high salt environment, E. tetradactylum juveniles was more adaptable to low-salt environment and could not survive in freshwater environment. The microstructure observation results showed that, at 10‰ salinity condition, the gill lamella of E. tetradactylum juveniles closely arranged closely, mitochondria-rich cells were distributed at the base of the gill patch. With the increase of salinity, the length and spacing of gill lamellae decreased, while the width of gill lamellae increased. At 5‰ salinity condition, the length, width and the intervals of gill lamella were 45.19±3.18 μm, 5.32±1.02 μm and 17.65±1.43 μm respectively. At 20‰ salinity condition, the length, width and the intervals of gill lamella were 36.67±3.81 μm, 8.78±2.22 μm and 11.56±3.81 μm respectively, the differences were all significant(P<0.05).At 20‰ salinity condition, mitochondrial rich cells could be seen at the distal end of the gill patch and the pavement epithelial cells appeared to be detached or separated. The surface scanning of the gills showed the mitochondrial rich cells could be divided into two subtypes:subtype Ⅰ(embolic apical crypts) and subtype Ⅱ(shallow apical crypts). Under 5‰salinity condition, there were two types of mitochondria-rich cells. Most of which were type Ⅱ, the apical membrane had a large opening and there were a large number of microvilli on the surface. The surface of pavement epithelial cells was uplifted by the microridge, forming a fingerprint-like circuit. Under 10‰ salinity condition, mitochondria-rich cells showed type Ⅰ structure, the microridge on the surface of pavement epithelial cells was irregular and the intercellular boundary distribution was not obvious. Under 15‰ and 20‰ salinity conditions, mitochondrial rich cells were dominated by type Ⅰ, with the change of salinity, the apical crypts gradually deepened, and the number of mitochondria-rich cells increased. The surface of the pavement epithelial cells had small ridges and the fingerprint-like circuit was not obvious.【Conclusion】When the water osmotic pressure changes, the survival rate and the number distribution and morphology of the cells on the gills of juvenile E. tetradactylum, the histological structure of gill are affected by environment salinity.

     

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