Abstract:The “land-sea-land” breeding pattern has become an important strategy for the rearing of Chinese sturgeon. In this study, juvenile Chinese sturgeon (Acipenser sinensis) in freshwater culture were utilized as the research object and an acclimation experiment was performed using continuous saltwater rearing conditions. To understand the adaptability changes of organs during osmoregulation, a comparative study was conducted on the structure of the gills, kidneys, and intestinal tissues of juvenile Chinese sturgeon grown in different salinities during seawater acclimation. The results showed that the survival rate of juvenile Chinese sturgeon in the seawater was 100%. During seawater acclimation, the breadth of the gill lamella significantly decreased (P<0.05), whereas the spacing of the gill lamella and chloride cell diameter significantly increased (P<0.05), suggesting that these juvenile Chinese sturgeon from a freshwater environment gradually adapted to a seawater environment by changing their gill lamella breadth and the space between the adjacent gill lamella, sped up their body and oxygen exchange capacity with the outside water conditions, and increased the chloride secretory cell sizes to improve the level of cell metabolism to cope in a water environment with high osmotic pressure. The glomerular diameter of the juvenile Chinese sturgeon decreased during seawater acclimation (P<0.05), and the number of glomerular decreased slightly; therefore, the juvenile Chinese sturgeon decreased the loss of body water by reducing the filtration function of their kidneys to adapt to the changes in osmotic pressure of the external environment. However, no obvious changes were observed in the intestinal tissue structure. The results showed that the juvenile Chinese sturgeon had strong seawater adaptability and osmotic adjustment of organs that adapted to the changes in seawater salinity by changing the breadth and spacing of their gill lamella, the size of the chlorine secretory cells, and the size and number of the glomerular.
