Marine cage culture leads to higher IMP content and ADSL gene expression in the muscle of Japanese sea bass ( Lateolabrax japonicus ) compared with freshwater pond culture

Abstract

Why seawater-reared Japanese sea bass (Lateolabrax japonicus) tastes better than that reared in freshwater has not been well determined. Given that flavour nucleotides have great impact on meat flavour, we compared the contents of AMP, GMP and IMP in the back muscle of Japanese sea bass cultured in marine cage and freshwater pond.The results showed that IMP was the main kind of flavour nucleotide and that the content of IMP in the back muscle of fish reared in seawater was significantly higher than that of fish reared in freshwater (p < 0.05). Quantitative real-time PCR analysis revealed that the transcript level of adenylosuccinate lyase (ADSL), a key player involved in IMP synthesis, was also significantly higher in marine cage cultured sea bass than that reared in freshwater pond (p < 0.05). These results suggest that marine cage culture may improve the content of IMP in the muscle of Japanese sea bass by enhancing the expression of ADSL gene, which makes sea bass taste better in turn. In addition, shear force test revealed that the tenderness of fish back muscle was significantly different between the two culture models. Since many environmental factors differ between marine cage culture and freshwater pond culture, more study is needed to elucidate the key factor and mechanism making this huge difference in IMP content.