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The farming of Scylla paramamosain with specific flavors has a higher commercial value, and the flavors are related to the integrated farming environment and non-volatile flavor substances, while the survival environment is one of the important ways to source gut microorganisms in the organism. In this study, the levels of dominant taxa in the gut flora of S. paramamosain from Mong Cai, Vietnam (VN), Taishan City, Guangdong Province (TS) of China, and Ninghai County, Ningbo City (NB) Zhejiang Province of China converged with those of S. paramamosain from Sanmen County, Ningbo City (CK1, CK2, and CK3) at 28 d of domestication. The top 15 genera with the highest abundance of VN, TS, and NB gut flora were the same as CK1, CK2, and CK3, but with different percentages, and gradually converged to CK1, CK2, and CK3, respectively, at 28 d of domestication. Correlation between intestinal flora and non-volatile flavor substances in the hepatopancreas at the percentage level of relative abundance of bacterial genera found that above 28 d of domestication, Muribaculaceae, Psychrilyobacter, Clostridia_vadinBB60_group, Halarcobacter Carboxylicivirga, Sediminispirochaeta may be the most important genera affecting flavor amino acids of VN. Sediminispirochaeta, Carboxylicivirga, Halarcobacter, Photobacterium, ZOR0006, Psychrilyobacter, and Pseudomonas may be the most important genera affecting flavor amino acids of NB. Sediminispirochaeta, Carboxylicivirga, Halarcobacter, Photobacterium, ZOR0006, Vibrio, and Sphingomonas may be the most important genera affecting flavor amino acids of TS. These results show that the intestinal flora structure of crabs from different areas were domesticated in the same area for at least 28 d before they converged to that of the domesticated crab, and the most important genera affecting the flavor amino acids of TS, VN, and NB were also identified. The results of this study provide a reference and basis for the technique of directional cultivation of the flavor quality of the crab. [ABSTRACT FROM AUTHOR]

The effects of low salinity on fatty acid and free amino acid (FAA) composition in muscles of swimming crab, Portunus trituberculatus, were investigated in this study. The swimming crabs were reared for 5 weeks under two different experimental treatments (the 12 ppt group and the 24 ppt group). Then, composition of fatty acids and free amino acids in total muscles was measured using gas chromatography–mass spectrometry (GC‐MS) with external standard method and liquid chromatography–mass spectrometer (LC‐MS) with internal standard method respectively. Results of fatty acid analysis showed that C18:1n9c, C20:5n3 (EPA) and C22:6n3 (DHA) were the dominating fatty acids in muscle tissues of P. trituberculatus. There was an extremely significant increase in contents of total fatty acids (TFA), total saturated fatty acids (SFA), total monounsaturated fatty acid (MUFA) and total polyunsaturated fatty acid (PUFA) in muscle tissues of P. trituberculatus with low salinity treatment (12 ppt) compared with those cultured in seawater (24 ppt) (p < 0.01). Results of free amino acid analysis showed that the content of total free amino acids (TFAA) significantly decreased in muscle tissues of P. trituberculatus with low salinity treatment compared with those in seawater (p < 0.05). Among all flavour‐tasting FAAs, the umami FAA content was extremely significantly higher in low salinity group compared with control group (p < 0.01); the sweetish FAA content was significantly lower in low salinity group while the bitter taste of FAA content had no significant differences between two groups. [ABSTRACT FROM AUTHOR]