Zhao Feng, Wu Beibei, Yang Gang, Zhang Tao, Zhuang Ping
Key Laboratory of Fisheries Ecology of the Yangtze Estuary, East China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, Shanghai, 200090, China.
Fish Physiol Biochem. 2016 Apr;42(2):749-56. doi: 10.1007/s10695-015-0172-4. Epub 2015 Nov 27.
Understanding the physiological changes and osmoregulatory strategy is critical for anadromous species to adapt to large changes between freshwater and marine environments. In this study, juvenile Chinese sturgeon (Acipenser sinensis) were acclimated for 2 months to freshwater (FW, c. 0‰) and brackish water (BW, 15‰). Blood was assessed for changes in osmolality and ions. Gill tissue was assayed for Na(+), K(+)-ATPase (NKA) activity and immunohistochemical analysis on mitochondria-rich cells (MRCs). Serum osmolality and ions concentrations (Na(+), Cl(-) and K(+)) examined, except K(+), increased significantly in those specimens adapted to BW. However, the variations were within the range of effective hyperosmotic adaptation. The specific activity of gill NKA of juveniles adapted to BW was significantly higher (c. 1.6 times) than that of fish adapted to FW. MRCs were mainly presented in the interlamellar region of the filament and at the base of the lamella in either FW- or BW-acclimated individuals. In BW, the number and size of MRCs on filaments greatly increased. However, there was no significant difference in the number and size of the MRCs at the lamella region. Results show that juvenile Chinese sturgeon keep osmotic homeostasis in hyperosmotic environments by increasing gill NKA activity and MRCs' size and number, which is similar to other sturgeons and euryhaline teleosts.
了解生理变化和渗透调节策略对于溯河洄游鱼类适应淡水和海洋环境之间的巨大变化至关重要。在本研究中，中华鲟幼鱼在淡水（FW，约0‰）和半咸水（BW，15‰）中适应2个月。评估血液中的渗透压和离子变化。检测鳃组织中Na(+)、K(+)-ATP酶（NKA）活性，并对富含线粒体的细胞（MRCs）进行免疫组织化学分析。除K(+)外，适应BW的中华鲟幼鱼血清渗透压和离子浓度（Na(+)、Cl(-)）显著升高，但变化在有效高渗适应范围内。适应BW的中华鲟幼鱼鳃NKA的比活性显著高于适应FW的个体（约1.6倍）。MRCs主要出现在丝状鳃小片的层间区域和鳃小片基部，无论是适应FW还是BW的个体。在BW中，丝状鳃小片上MRCs的数量和大小显著增加。然而，鳃小片区域MRCs的数量和大小没有显著差异。结果表明，中华鲟幼鱼通过增加鳃NKA活性以及MRCs的大小和数量，在高渗环境中维持渗透平衡，这与其他鲟鱼和广盐性硬骨鱼类似。
