Na+/K+-ATPase is an important ion-transporting enzyme involved in osmoregulation. The swimming crab (Portunus trituberculatus) is a commercially important edible crab species in China. At salinities lower than 10 or higher than 40, its production is seriously impacted; however, the mechanisms of how the Na+/K+-ATPase of swimming crabs responds to salinity changes, is unclear. In the current study, the Na+/K+-ATPase α-subunit (NAKA) and β-subunit (NAKB) cDNA of P. trituberculatus was identified. Multiple alignment was performed and the expression of NAKA and NAKB in the 6th gills under different salinity conditions were detected using semi-quantitative RT-PCR. The results showed that NAKA and NAKB mRNA both increased significantly at day 1, but they were maintained at low levels when exposed to 40 salinity for a long time. The hematoxylin and eosin staining showed that ionocytes increased in size at 40 salinity, but decreased at 10 salinity. Immunocytochemical analysis revealed that NAKA signals increased with exposure to 40 salinity for one day, but the signals were not strong at 10 salinity. Comparison of the conserved NAKA domain of P. trituberculatus and the Chinese mitten crab (Eriocheir sinensis) showed that the polypeptide binding site (α-subunit/β-subunit interface) was different, which may be one of the reasons that P. trituberculatus is not as tolerant of fresh water as E. sinensis.
The Japanese mitten crab Eriocheir japonica is an economically important species widely distributed throughout the East Asia region, but information on the compositional characteristics and nutritional quality of E. japonica is still scarce. Thus, this study was conducted to compare the edible tissue indices, proximate composition, fatty acid profiles and amino acid contents between wild E. sinensis and E. japonica. It showed that: (1) both E. sinensis and E. japonica have a high total edible yield (approximately 40%); (2) E. sinensis and E. japonica have a similar proximate composition, except for total lipids; (3) female E. japonica have higher percentages of C18:3n3, C20:5n3 and C22:6n3; (4) E. sinensis have higher levels of essential amino acids than E. japonica in muscle. In conclusion, these results demonstrated that wild E. japonica is rich in omega-3 fatty acids, and both E. sinensis and E. japonica are aquatic food of high nutritional value, with a high edible yield.
Lipopolysaccharide-induced TNF-α factor (LITAF) is an important transcription factor mediating the expression of inflammatory cytokines, including TNF-α, which is involved in the innate immune defence against infectious agents. In this study, the Scylla paramamosain LITAF (LITAF) gene was cloned and identified from S. paramamosain using RT-PCR and RACE. The full length cDNA of LITAF was 1116 bp, contained an ORF of 495 bp encoding a polypeptide of 164 amino acids with predicted molecular mass of 17.86 kDa and a theoretical isoelectric point of 8.51. Sequence alignment showed that LITAF possessed a typical LITAF domain with two CXXC motifs and eight conserved cysteine residues. Phylogenetic analysis indicated that LITAF clustered closely with known LITAFs from Eriocheir sinensis and Litopenaeus vannamei. qRT-PCR analysis showed LITAF mRNA transcript expressed ubiquitously in all examined tissues with the highest expression in haemocytes, while lower expression in hepatopancreas. Its expression levels displayed a trend of up-regulation and then returned to its initial value in haemocytes and gill, post challenge with LPS, Poly (I : C), and Vibrio alginolyticus, respectively. Furthermore, the LITAF protein was verified to be located in hyalinocytes, semi-granulocytes and granulocytes, and was distributed throughout the cytoplasm and nucleus, especially in cytoplasm. These results provide a basis for further investigating the roles of LITAF in the immune signaling pathways as a transcription factor in S. paramamosain.
The objective of this study was to investigate the effects of Caulerpa racemosa (Agardh, 1873) polysaccharides (CRP) on non-specific immunity of the white shrimp, Litopenaeus vannamei (Boone, 1931). The extracted polysaccharide consists of galactose, glucose, and mannose. Total polyphenolic compound and total flavonoids content in CRP were determined. In vitro CRP treatment did not alter cell viability of haemocytes and significantly activated phenoloxidase (PO) activity, superoxide anion production capacity, phagocytic rate, and index in haemocytes. Immune parameters, such as total haemocyte count, PO activity, phagocytosis, and superoxide anion production, were significantly elevated in CRP-fed shrimp during the rearing period. Malondialdehyde levels in the hepatopancreas of CRP-fed shrimp were lower than in control shrimp from day 7 to day 28. These results show that CRP exhibits antioxidant activity and can activate immune responses of white shrimp in vitro and in vivo. Therefore, CRP can be considered a functional feed additive to improve white shrimp immunity.
This study was to examine the immunomodulatory effects of oxytetracycline (OTC) on the white shrimp Litopenaeus vannamei (Boone, 1931). Immune parameters were not suppressed by OTC treatment in haemocytes in vitro. A total of 96 healthy shrimp were divided into four groups. Group 1 was the control group. Group 2 received 50 mg OTC/kg body weight/day. Group 3 received 1 g β-glucan/kg feed. Group 4 received 50 mg OTC/kg body weight/day and 1 g/kg β-glucan. OTC residues were more highly accumulated in the hepatopancreas than in muscle tissue during the rearing period, and the addition of β-glucan prolonged the retention time of OTC in the muscle tissue. Additionally, dietary administration of OTC in combination with β-glucan facilitated the excretion of OTC from the hepatopancreas. Shrimp that orally ingested OTC alone had an elevated total haemocyte count, phagocytosis, superoxide anion production and prophenoloxidase activity, and these immunostimulatory effects were further enhanced in shrimp receiving OTC in combination.