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In order to reveal the influence of overwintering behaviour on the flavour of Scylla paramamosain, this study selected crabs of before and after overwintering in SM (Sanmen County, Zhejiang Province), HP (Hepu County, Guangxi Province) and WN (Wanning city, Hainan Province). The contents of flavouring‐related substances in hepatopancreas, muscles and gonads were determined by high‐performance liquid chromatography (HPLC); taste activity value (TAV) and equivalent umami concentration (EUC) were calculated. The results showed that sweetish amino acids were mainly accumulated in muscles, umami amino acids were mainly accumulated in hepatopancreas, free nucleotides were mainly accumulated in gonads, and the EUC value in gonads was the highest. After overwintering, the content of sweetish, umami amino acids and free nucleotides in muscle and hepatopancreas decreased significantly, while the content of flavour‐tasting amino acids in gonads did not change significantly, but the content of umami nucleotides increased significantly. Therefore, overwintering behaviour decreased the flavour of muscle and hepatopancreas, slightly enhanced gonad and the overall flavour of S. paramamosain before overwintering was better than that after overwintering. [ABSTRACT FROM AUTHOR]

Scylla paramamosain is one of the commercially crucial marine crustaceans belonging to the genus Scylla, which is commonly distributed along the coasts of China. Proteomic data are scarce for the mud crab. Salinity is one of the ecological factors that affect S. paramamosain during overwintering. To understand the energy metabolism mechanism adapted to salinity, we analysed the proteomics of S. paramamosain hepatopancreas in response to two different salinities (4‰ and 25‰). A total of 1283 proteins were detected, of which 426 down‐regulated proteins and 83 up‐regulated proteins were associated with metabolism (p < 0.05). Among these proteins related to metabolic pathways (16 pathways), we identified angiotensin‐converting enzyme, trypsin, glutamate dehydrogenase, aminomethyl transferase, hexokinase, pyruvate kinase, glucose‐6‐phosphate dehydrogenase, L‐lactate dehydrogenase, superoxide dismutase, alkaline phosphatase, catalase and xanthine dehydrogenases. Additionally, real‐time PCR showed mRNA expression of differentially expressed genes correlated positively with their protein levels. Compared with 25‰ salinity group, 4‰ salinity group was involved in amino acid metabolism, carbohydrate metabolism, energy metabolism, lipid metabolism and inorganic ion metabolism by regulating related proteins, which made the metabolism of the overwintering S. paramamosain more vigorous in the low salt environment, and hepatopancreas consumed more energy to maintain life activities. These data are the first to reveal the molecular mechanism of overwintering S. paramamosain in response to different salinities at the protein level. The study provides important information for the aquaculture production of S. paramamosain during indoor overwintering. [ABSTRACT FROM AUTHOR]

Overwintering is an important part of the conservation of Scylla paramamosain, and salinity is a primary parameter affecting this species' metabolism at this particular time. We compared and analysed gene sequences responsible for the metabolism of S. paramamosain at 4‰ versus 25‰ salinities using transcriptome analysis, in order to find out the optimum salinity for S. paramamosain during overwintering. A total of 5895 genes were detected, of which 105 down‐regulated genes and 131 up‐regulated genes were associated with metabolism (p < 0.05). Among these genes related to metabolic pathways (117 pathways), we identified D‐aspartate oxidase, D‐amino acid oxidase, creatine kinase, sarcosine oxidase, citrate synthase, transferase, glycogen synthase, hexokinase, carbonic anhydrase, glutamine synthetase, V‐type H+‐transporting ATPase, 3′‐phosphoadenosine 5′‐phosphosulphate synthase, fatty acid synthase and others. Additionally, the consistency between qRT‐PCR results and transcriptome data reflected the reliability of transcriptome results in the present study. Compared with the 25‰ salinity group, the 4‰ salinity group promoted energy metabolism, amino acid metabolism, lipid metabolism and carbohydrate metabolism by regulating metabolism‐related genes, which made the overwintering S. paramamosain more active in the low‐salt environment, and hepatopancreas consumed more energy to maintain life activities. These results improve our understanding on molecular mechanisms and metabolic pathways associated with salinity changes in S. paramamosain during overwintering. The data presented in this study are also the first to reveal the molecular mechanisms of S. paramamosain during overwintering in response to different salinities at the gene level. [ABSTRACT FROM AUTHOR]

Overwintering is one of an important stage for aquatic animals, and light intensity has an important effect on the conservation of Scylla paramamosain during overwintering. Three different light intensity levels (0, 1.43 and 40.31 μmol m−2 s−1) were used to explore the effects of light intensity on digestion and immune responses, plasma cortisol and amino acid composition of S. paramamosain. This is the first report that the adult S. paramamosain can be effect by the light intensity. The results showed that S. paramamosain has a strong stress response under high light intensity. Compared with darkness condition, digestive enzyme activity was higher under light condition. S. paramamosain reared under low light conditions had enhanced immunity, and it raised in light conditions exhibited superior qualities to those cultured in dark conditions. The results of this study demonstrated that low light levels are most suitable for breeding and improving the quality of S. paramamosain. [ABSTRACT FROM AUTHOR]

Overwintering is an important part of the conservation of Scylla paramamosain, and salinity has an important effect on the conservation of S. paramamosain during overwintering. Three salinities (4‰, 12‰ and 25‰) were selected as the overwintering salinities to reveal the effects of different salinities on the relevant important ions in osmotic pressure regulation, plasma cortisol, digestive enzymes, immune enzymes and amino acids of S. paramamosain during indoor overwintering. Results indicated that after overwintering, Cl‐, Na+ and the osmotic pressure of serum have the highest salinity at 25‰, and the lowest salinity at 4‰. Na+/K+‐ATPase activity and cortisol were found to increase with decreasing salinity. The activity of digestive and immune enzymes was highest at 25‰, and was the lowest at 4‰. The amount of total amino acids (TAA), umami amino acids (UAA) and essential amino acids (EAA) in 25‰ were significantly higher than in 4‰ and 12‰. After overwintering, the essential amino acid index (EAAI) in the salinity range of 12–25‰ was 54.04–59.00, compared to 48.56–54.04 in the salinity range of 4–12‰. As a result, S. paramamosain at 25‰ had higher digestion and immunity than at 4‰ and 12‰, due to requiring more energy for osmotic pressure adjustment. In addition, S. paramamosain at 25‰ had the best meat quality. The results of this study are helpful for aquaculture production for indoor overwintering of S. paramamosain. [ABSTRACT FROM AUTHOR]

Three salinities (4‰, 12‰ and 25‰) were selected to determine the effects of different salinities on the growth, survival, nutrition and energy metabolism of Scylla paramamosain during indoor overwintering. Growth performance (survival rate, condition factor, hepatopancreatic index, weight gain rate and specific growth rate), nutrient composition (ash, moisture, crude fat, crude protein and total nitrogen), fatty acids, energy metabolites (glycogen, glucose, triglycerides, cholesterol and lactic acid) and energy metabolic enzymes (hexokinase, pyruvate kinase, lactate dehydrogenase and succinate dehydrogenase) were measured and calculated. The results showed that S. paramamosain exhibited the best growth and survival at 25‰ and worst at 4‰ after overwintering. In addition to consuming crude fat, excess protein was also broken down to provide energy in the 4‰ and 12‰ groups. The content of unsaturated fatty acids in the 25‰ group was higher after overwintering. Glycogen and glucose consumption and triglycerides, cholesterol and lactic acid production were lowest in the 25‰ group. The activity of hexokinase, pyruvate kinase, lactate dehydrogenase and succinate dehydrogenase was highest in the 4‰ group and lowest in the 25‰ group. The activity of hexokinase, pyruvate kinase, lactate dehydrogenase and succinate dehydrogenase in the hepatopancreas was higher than in the muscle. In conclusion, S. paramamosain uses less energy, has more unsaturated fatty acids and has a higher survival rate at a salinity of 25‰ after overwintering. The results of this study provide helpful information the indoor overwintering S. paramamosain in aquaculture production systems. [ABSTRACT FROM AUTHOR]

An "abnormal" female Scylla paramamosain, named "Butter crab" (B_♀) is more popular than wild‐type mud crab (CK) with people. Histologically, "butter crab" ovaries are partially degraded, with full of yellow oily substances in body. Composition of the essential nutritional components is quite similar in "butter crab" and CK. In a comparison of fatty acids, B_♀ is richer. A comparison of flavour amino acids and nucleotide in muscle showed that sweet amino acids and bitter amino acids in B_♀ is lower than CK_♀, but umami amino acids are significantly higher in B_♀. However, the umami amino acid content in the gonads is significantly less in B_♀ than CK_♀. Moreover, umami nucleotides in B_♀ muscle is significantly higher. From the perspective of EUC evaluation, the umami taste of CK_ ♀ gonads is strongest, followed by B_ ♀ gonads. In the hepatopancreas, the umami taste ranks CK_♀> B_♀ >CK_♂, and there are no significant differences among muscles in the three groups. In conclusion, the characteristics of "butter crab" are more fragrant and nutritious, with sweet and umami taste. The article systematically scientifically analysed the nutritional composition and flavour characteristics of "butter crab", providing a novel insight for development of S. paramamosain industry. [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]

The article offers information on the effect of tank colour on growth performance, stress response and carapace colour of juvenile swimming crab, Portunus trituberculatus. Topics discussed include information on the culturing of crab in indoor or pond, leading to increased demand of seedling; and the discussions on the tank colour as a non‐dynamic rearing factor which reduce the stress responses as well as enhance the growth performance.