Comparison on nutritional quality of adult female Chinese mitten crab (Eriocheir sinensis) with different colored hepatopancreases

Comparison of Body Characteristics, Carotenoid Composition, and Nutritional Quality of Chinese Mitten Crab (Eriocheir sinensis) with Different Hepatopancreas Redness

In this study, we investigated the body characteristics, carotenoid composition, and nutritional quality of Eriocheir sinensis with different hepatopancreas redness (a*). We distributed the crabs into two groups based on the hepatopancreas a* values and compared their body characteristics, chroma, carotenoid composition, and protein, lipid, total sugar, amino acid, and fatty acid content via paired t-test. The results revealed that the relationships between hepatopancreas a* values and crab quality are sex specific. In female crabs, the differences in nutritional characteristics were evident mainly in the hepatopancreases and ovaries. In the redder hepatopancreases, the content of zeaxanthin and β-carotene increased, and the levels of C22:6n3 and C20:5n3 decreased (p < 0.05). In the ovaries, the content of astaxanthin, canthaxanthin, β-carotene, umami, and sweet amino acids were lower in the redder hepatopancreas crabs (p < 0.05). In male crabs, there were positive relationships between hepatopancreas a* and amino acid and fatty acid content. The content of leucine, arginine, and total umami amino acids in muscles and of unsaturated fatty acids and n-6 polyunsaturated fatty acids in hepatopancreases and testicles increased with increasing hepatopancreas a* values (p < 0.05). Therefore, the redder the hepatopancreas, the higher the nutritional quality of male crabs.

Comparative Study on Growth Index and Nutritional Quality of Female Chinese Mitten Crab Eriocheir sinensis Selected at Different Growth Periods in Rice-Crab Culture Systems

Research was conducted on the growth performance and nutritional quality of Chinese mitten crabs (Eriocheir sinensis) during a 62-day growing period in a symbiotic coculture comprising rice and crab. Culture experiments were conducted in three rice fields of equal size (996 m²). On days 0 (July 15, D0), 15 (July 30, D15), 31 (August 15, D31), 46 (August 30, D46), and 62 (September 2, D62), tissue samples of 50 female E. sinensis were collected randomly from each rice field. The results showed that the serum growth hormone (GH) content and muscle ecdysone receptor (EcR) mRNA expression levels were higher in the D31 and D46 groups; the content of serum 20-hydroxyecdysone (20-HE) and the mRNA expression levels of retinoid X receptor (RXR), insulin-like growth factor 2 (IGF2), and chitinase (CHI) reached the maximum in the D31 group. Muscle crude protein content gradually increased; hepatopancreas crude protein and crude lipid content began to decrease after reaching the maximum value in the D0 and D15 groups, respectively; the contents of crude protein and crude lipid in the ovary significantly increased in the D46 and D62 groups (P < 0.05). The content of muscle essential amino acids (EAA) reached the maximum in the D46 group; the hepatopancreas EAA content began to decrease significantly in the D31 group (P < 0.05); and the EAA content of the ovary decreased significantly after reaching the maximum value in the D46 group (P < 0.05). The muscle contents of eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), docosahexaenoic acid (DHA), polyunsaturated fatty acids (PUFA), and n-3 polyunsaturated fatty acids (n-3PUFA) and the ratio of n-3 polyunsaturated fatty acids/n-6 polyunsaturated fatty acids (n3/n6) decreased significantly in the D31 group (P < 0.05); the hepatopancreas contents of EPA, PUFA, n-3PUFA, and n-6 polyunsaturated fatty acids (n-6PUFA) and the ratio of n3/n6 began to decrease after reaching the maximum value in the D31 group, ethyl behenate (21:0), tetracosanoic acid (24:0), DPA, and DHA contents were detected for the first time in the D31 group; the ovary PUFA, n-3PUFA contents, and n3/n6 ratio of the D46 and D62 groups were significantly lower than those of the D31 group (P < 0.05). During the experimental conditions described here, female E. sinensis raised in rice fields reached rapid growth from August 15 to August 30. Additionally, the nutritional quality of the female E. sinensis edible tissues (muscle, hepatopancreas, and ovary) began to decline after August 15, when sufficient nutrients such as protein, lipid, EAA, and PUFA should be provided to the female E. sinensis.

Hepatopancreas immune response during different photoperiods in the Chinese mitten crab, Eriocheir sinensis

Photoperiod plays an important role in the growth, development, and metabolism of crustaceans. The growth and reproduction of crabs are closely related to the photoperiod. The hepatopancreas is an important source of innate immune molecules; however, hepatopancreatic patterns of gene expression depending on the photoperiod-which may underlie changes in immune mechanisms-remain unknown. To study the molecular basis of immune regulation in the Chinese mitten crab (Eriocheir sinensis) under different light conditions, a new generation of high-throughput Illumina sequencing technology was used, and functional genes associated with immune function in the hepatopancreas of this crab were explored via assembly of high-quality sequences, gene annotation, and classification. A total of 383,899,798 clean reads from the hepatopancreas of the normal group (12 h/12 h L:D), 387,936,676 clean reads from the continuous light group (24 h/0 h L:D), and 384,872,734 clean reads from the continuous darkness group (0 h/24 h L:D) were obtained. Compared with the normal group, 141, 152, 60, 87, 90, and 101 differentially expressed genes were identified in the groups exposed to continuous light for 2 days, continuous darkness for 2 days, continuous light for 4 days, continuous darkness for 4 days, continuous light for 6 days, and continuous darkness for 6 days, respectively. The results of this study revealed that under continuous light and dark conditions, the crabs were most affected by light on day 2, but the interference gradually decreased with time. We suggest that long-term light or dark treatment makes crabs adaptable to fluctuations in the photoperiod. The expression of genes associated with immune response patterns was found to change during different photoperiods. Prophenoloxidase (proPO) and serine proteinase (kazal-type serine proteinase inhibitor 1 and serine proteinase inhibitor-3) in the proPO-activating system were significantly upregulated in the 2-day continuous light group. Glutathione peroxidase 3 was significantly downregulated under continuous light exposure, while cyclooxygenase was upregulated in the continuous light and dark environments. These results provide insights into the molecular mechanism underlying the effects of the photoperiod on immune regulation and the physiological activity of E. sinensis.

Comparative study of female Chinese mitten crabs based on their sizes and weights

The Chinese mitten crab (Eriocheir sinensis) is an important aquaculture species in China. While the price of a large crab will generally be 2-5 times higher than that of smaller crabs, it remains unknown whether nutritional quality is affected by market price. To investigate the effect of size on nutritional composition, adult female crabs were collected and assigned to grades I-IV according to decreasing size. The results showed that meat yield and conditional factors were significantly (P < 0.05) reduced with the decreasing size. The different sizes did not significantly (P > 0.05) affect levels of moisture, crude protein (except for hepatopancreatic crude protein), and total lipid. Grade III crabs had the largest hepatopancreatic crude protein level, which was significantly (P < 0.05) increased compared with grade I crabs. A balanced amino acid composition was found in grade IV crabs, while crabs from grades II and IV had the highest essential amino acids score. Levels of highly unsaturated fatty acids, including C22:6n3, and the ratios of n-3 polyunsaturated fatty acids (PUFA)/n-6 PUFA and C22:6n3 (DHA)/C20:5n3 (EPA) in the hepatopancreas were significantly (P < 0.05) increased in grade III crabs compared with the other grades. In conclusion, among the four grades smaller female crabs (average weight: 93-112 g, grades III-IV) displayed an optimal nutritional quality.