Short‐term exposure to 5‰ and 15‰ salinity causes the dynamic changes of the NKA gene, enzyme activities and morphological characteristics in fish tissues of Gymnocypris przewalskii

Abstract

Salinity affects the physiological activities of aquatic animals and determines the distribution of fish. In this study, we found that the naked carp survived under 0–15‰ salinity, but survival rates decreased to varying degrees under 20‰ and 25‰ salinity, which indicates that the safety threshold of salinity tolerance of Gymnocypris przewalskii is 0–15‰. Next, the response rate of NKAα1 in the gills and kidneys was significantly faster than in the livers, and the response intensity of NKAα1 and NKAα3 has certain tissue specificity under different salinity. NKA enzyme activity first increased, then gradually decreased and increased again in the gills and kidneys after 5‰ and 15‰ salinity stress. In contrast, the NKA enzyme activity gradually decreased and then gradually increased in the liver. Salinity stress also could lead to some pathological phenomena in the cytoplasm. These results indicated that changes in salinity can lead to differential expression of the NKA genes and enzyme in tissues. Also, the dynamic changes of the NKA gene, enzyme activities, and morphological characteristics in fish tissues are in response to the salinity changes in the living environment, thus maintaining a dynamic balance of ions inside and outside the cells.