The immuneoreaction and antioxidant status of Chinese mitten crab (Eriocheir sinensis) involve protein metabolism and the response of mTOR signaling pathway to dietary methionine levels

In vitro immune analysis of serum from the hemolymph of the anomuran crab Albunea symmysta (Linnaeus, 1758) displayed diversified reactions

The present investigation aims to substantiate that serum from the hemolymph of anomuran crab Albunea symmysta encompasses multiple immunological reactions in in vitro condition. The serum highly agglutinated human O erythrocytes in the presence of Ba2+. Distinct and unique sugar binding capacity of serum towards laminarin, N-acetyl sugars and higher binding specificity towards a glycoprotein, fetuin was inferred. In vitro enhancement of melanin synthesis due to enhanced oxidation of 3, 4-dihydroxy-dl-phenylalanine (dl-DOPA) by preincubation of nonself molecules with serum phenoloxidase (PO) was documented. Similarly, dl-DOPA oxidation by serum PO was reduced when preincubated with chemical inhibitors and copper chelators. Further, the crab serum lysed the vertebrate erythrocytes with maximum hemolysis against chicken and it unveiled dependency on divalent cation, serum concentration, ionic strength, pH, temperature and time interval. Occurrence of maximum hemolysis at a concentration of 30 µl, pH 8.0, temperature 37 °C and time interval of 60 min in the presence of Ba2+ were documented. Interestingly, serum hemolysis was reduced by different osmoprotectants suggesting a colloid-osmotic mechanism involving in hemolysis. It was observed that A. symmysta serum had antimicrobial activity against Gram-positive Staphylococcus aureus and fungal pathogen Candida albicans. The serum showed higher glycan content, potent lysozyme and free radical scavenging activity suggesting the existence of potential immune molecules of therapeutic use. These results clearly demonstrated the diversified immunogenicity of A. symmysta serum confirming a highly conserved non-specific immunity of crustaceans.

The influence of dietary Coenzyme Q10 on growth performance, antioxidant capacity and resistance against Aeromonas hydrophila of juvenile European eel (Anguilla anguilla)

The present study was conducted to investigate the effects of dietary Coenzyme Q10 (CoQ10) on the growth performance, body composition, digestive enzyme activity, antioxidant capacity, intestinal histology, immune-antioxidant gene expression and disease resistance of juvenile European eel (Anguilla anguilla). Fish were fed a diet supplemented with CoQ10 at concentrations of 0, 40, 80 and 120 mg/kg for 56 days. The results indicated that dietary CoQ10 supplementation did not significantly affect final body weight (FBW), survival rate (SR), weight gain (WG), feed rate (FR), viscerosomatic index (VSI) or hepatosomatic index (HSI) among all experimental groups. However, the highest FBW, WG and SR were found in the 120 mg/kg CoQ10 group. Dietary 120 mg/kg CoQ10 markedly improved feed efficiency (FE) and the protein efficiency ratio (PER). The crude lipids in the body and triglycerides (TG) and total cholesterol (TC) in serum were obviously lower in the 120 mg/kg CoQ10 group than in the control group. For digestive enzymes, protease activity in the intestine was markedly boosted in the 120 mg/kg CoQ10 group. The serum activities of SOD, CAT and GST in the 120 mg/kg CoQ10 group were significantly higher than those in the control group. Dietary 120 mg/kg CoQ10 efficiently enhanced superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST) activities in the liver, while the malondialdehyde (MDA) content was significantly decreased. No significant histological changes in the liver were identified in any group. Dietary supplementation with 120 mg/kg CoQ10 improved antioxidant capacity and immunity by upregulating the expression of cyp1a, sod, gst, lysC, igma1, igmb1 and irf3 in the liver. Furthermore, the cumulative survival rate of juvenile European eel against challenge with Aeromonas hydrophila was significantly elevated in the 80 and 120 mg/kg CoQ10 supplemented groups. Conclusively, our study suggested that supplementing the diet of juvenile European eel with CoQ10 at a concentration of 120 mg/kg could promote their feed utilization, fat reduction, antioxidant capacity, digestibility, immune-antioxidant gene expression and resistance to Aeromonas hydrophila without negative effects on fish health status.

Dietary Methionine Level Impacts the Growth, Nutrient Metabolism, Antioxidant Capacity and Immunity of the Chinese Mitten Crab (Eriocheir sinensis) under Chronic Heat Stress

This study examined whether diets with high dietary methionine levels could alleviate chronic heat stress in Chinese mitten crab Eriocheir sinensis. Crabs were fed three dietary methionine levels of 0.49%, 1.29% and 2.09% for six weeks. The analyzed methionine concentration of diets was 0.48%, 1.05% and 1.72%, respectively. Crabs were fed three different supplemental concentrations of dietary methionine at 24 °C and 30 °C, respectively. The trial was divided into six groups with five replicates in each group, and 40 juvenile crabs (initial average weight 0.71 ± 0.01 g) in each replicate. During the trial, crabs were fed twice daily (the diet of 4% of the body weight was delivered daily). The effects of dietary methionine level on nutrient metabolism, antioxidant capacity, apoptosis factors and immunity were evaluated at a normal water temperature of 24 °C and high temperature of 30 °C. Feed conversion ratio decreased under chronic heat stress. Chronic heat stress increased weight gain, specific growth rate, molting frequency, and protein efficiency ratio. The survival of crabs decreased under chronic heat stress, whereas a high level of dietary methionine significantly improved survival. Chronic heat stress induced lipid accumulation and protein content reduction. The high-methionine diet decreased lipid in the body and hepatopancreas, but increased protein in the body, muscle and hepatopancreas under chronic heat stress. Simultaneously, the high dietary methionine levels mitigated oxidative stress by reducing lipid peroxidation, restoring the antioxidant enzyme system, decreasing apoptosis and activating immune function under chronic heat stress. This study suggests that supplementing 1.72% dietary methionine could alleviate the adverse effects of a high water temperature in E. sinensis farming.