Different biochemical composition and nutritional value attribute to salinity and rearing period in male and female mud crab Scylla paramamosain

Crabs show major differences in biochemical composition and nutritional value responding to various culture environments, growth stages and even sexes. In the present study, juvenile mud crab Scylla paramamosain (0.026 +/- 0.010 g) were cultured at two earthen ponds with the respective salinity level of 25 parts per thousand and 5 parts per thousand for four months. The proximate composition, amino acid content and fatty acid profile in edible parts (muscle and hepatopancreas) of male and female crabs reared at different salinities and two rearing periods (three-month stage: 60-120 g and four-month stage: 150 300 g) were investigated and compared. Crabs at high salinity had significantly lower moisture contents in muscle and hepatopancreas, but had higher protein contents in muscle and higher ratio of n-3/n-6 highly unsaturated fatty acids (PUFA) in both edible parts, regardless of gender and rearing period. Additionally, significant differences in biochemical composition and nutritional value were also found between male and female crabs. For example, the contents of crude protein and most amino acids were higher in muscle and hepatopancreas of females, whereas males contained higher n-3 PUFA contents in both edible parts. Further, the contents of delicious amino acids (DAA) and essential amino acids (EAA) in muscle and the crude lipid content in hepatopancreas exhibited a higher trend at three-month stage than that at four-month stage. The results suggested that S. paramamosain reared at high salinity had better nutritional value than that at low salinity, while female and male crabs possess their respective advantages in terms of different nutritional composition. In addition, crabs had a better nutritional quality at three-month stage, even though they were at a smaller size.