Salinity acclimation alters acid and alkaline phosphatase expression and histological changes in the hepatopancreas of the oriental river prawn Macrobrachium nipponense (De Haan, 1849) (Decapoda: Caridea: Palaemonidae)

Abstract

Abstract The oriental river prawn, Macrobrachium nipponense (De Haan, 1849), an economically important species, can live in freshwater and brackish water environments, but molecular mechanism of adaptation to varying salinity levels is still poorly understood. We aimed to investigate the effects of four different salinities (0, 6, 12, and 18‰) on metabolic responses, histological structure, and expression patterns of acid phosphatase (ACP) and alkaline phosphatase (AKP) in the hepatopancreas. The full-length cDNAs of ACP and AKP of M. nipponense (designated MnACP and MnAKP, respectively) were obtained by rapid-amplification of cDNA ends (RACE)-PCR. Immunofluorescence experiments confirmed that MnAKP is located in the cell membrane of the hepatopancreas. Both genes were expressed in all seven studied tissues, with highest expression in the hepatopancreas by quantitative real-time PCR. The mRNA expression levels and enzyme activities of MnACP and MnAKP in the hepatopancreas significantly increased in 18‰ salinity group compared to other groups. Measurements of glycogen, triglycerides, and total cholesterol levels suggested that prawns can adjust the energy metabolism in a way to provide additional energy under unsuitable salinity. Besides, prawns at high salinity produced higher B-cells and lower number of R-cells in hepatopancreatic tubules, also suggesting enhance the metabolic function of the hepatopancreas under high salinity. Our results provide a better understanding for the mechanism regulating salinity acclimation in the oriental river prawn.