Effects of low-salinity acclimation on the Na+/K+ ATPase activity and expression of osmoregulatory-related genes in large yellow croaker (Larimichthys crocea)

Abstract

Large yellow croaker (Larimichthys crocea) is one of the most commercially important marine fish in southeast China. The white spot disease frequently occurs in large yellow croaker leading to a devastating loss. Given that the pathogen, Cryptocaryon irritans, hardly survive in the low-salinity environment, the low-salinity farming is a potential strategy to defend large yellow croaker. In this study, the water salinity was consecutively decreased from 28 ‰ to 0 ‰, during which the survival rate of L. crocea was stable from 28 ‰ to 4 ‰, while a higher mortality was observed at < 4 ‰. The NKA activity in the kidney and gill of L. crocea was significantly stimulated by the decrease of water salinity from 28 ‰ to 4 ‰ and gradually dropped to the baseline, which was associated with variations of the expression level of NKAα1 and NKAβ1. The expression profile of PRLR was consistent with NKAα1 and NKAβ1, which implied that they might be the targets of PRL in L. crocea in response to the challenge of salinity variations. The other two osmoregulatory-related genes, NHEβ and NCC, significantly increased at low water salinity (< 4 ‰) in both the kidney and gill, which likely dedicated the sodium reabsorption at low water salinity. Our findings would provide new insights into osmoregulation of the kidney and gill in the large yellow croaker in response to the challenge of lowing water salinity.