The response and osmotic pressure regulation mechanism of Haliotis discus hannai (Mollusca, Gastropoda) to sudden salinity changes

Abstract

Salinity is one of the critical ecological factors which will impact the growth and development of marine shellfish. With the rapid expansion of aquaculture area for Haliotis discus hannai, the frequent summer rainstorms in South China, the influx of freshwater, or the strong volatility of seawater in coastal areas, inner bays have placed abalone into the dynamic environment where the salinity is changing drastically. This work examined the effects of sudden salinity changes on abalone’s survival, osmotic pressure regulation, energy metabolism, and related gene expression by simulating the salinity changes of water for breeding H. discus hannai caused by heavy storm. The salinity was gradually reduced from 30 to 20, then kept at 20 for 48 h, followed by gradual increase to 30, and was kept at 30 for 48 h. Samples were taken at 6, 12, 36, 60, 66, 72, 96, and 120 h after the start of the experiment, respectively. Results showed that the survival rate of abalone at 120 h was significantly lower than that at any other time except at 96 h (P 0.05). The expression levels of catalase, thioredoxin peroxidase, sigma-glutathione-s-transferase, and Mu-glutathione-s-transferase significantly rose with the salinity changes, and were significantly higher than that in the control group up to the end of the experiment (P < 0.05). As sudden salinity changes may cause some abalone deaths, the enhanced activity of related enzymes and the increase of gene expression levels might be one of the effective methods for an organism to respond to salinity stress and regulate osmotic pressure.