Effect Of Dietary Fatty Acid Nutrition On The Immunological Ability And Resistance To Hypoxia In Chinese Mitten Crab (eriocheir Sinensis)

Chinese mitten crab (Eriocheir sinensis) is called hair crab, river crab, is belong to crustacea class, decapoda order, square crab family, and mitten crab genus, is a specialty in China. It mainly lives the coast of Chinese eastern sea and the rivers, lakes connected with sea, now is a main aquaculture economic crabs species in China. Recent years, the annual yield of market-sized mitten crabs increased from 17 500mt in 1993 to 570 000mt in 2005. The pond aquaculture is the main form of farming crabs in China. In this kind aquaculture process, especially in hot weather, the organic waste such as abundant residual feed and excretion deposited at the bottom of the pond and could not be decomposed, meanwhile, the pond commonly did not clear up for several years. These all lead to the occurence of oxygen consumption at the bottom of the pond, the crabs lived in the benthic cave of pond were subjected to the hypoxia stress. At hypoxia condition, the immune abilities of crabs could reduce, and its resistance to disease would decrease, then they will die due to the infection. Another, the reduction of immune abilities would influence crabs'anti-hypoxia ability, the interaction of both factors led to massive death of mitten crabs in Chinese ponds.Improvement of crab nutrition, the research about the relationship of environmental stress tolerance and nutrition are an important way to enhancing the ability of immune and anti-hypoxia in crabs. Essential fatty acids (EFA) such as DHA, ARA and EPA et al. play a diverse role in the physiological and biochemical processes within aquatic animals. EFA is an important component in cell membrane, can influence the cellular phagocytosis and respiratory burst strength, and increase the aquatic animals'immune ability with regulating the enzymes relating to immune. In addition, the DHA and EPA is the precursors of eicosanoids, the eicosanoids is a kind of highly reactive molecules in a variety of stress response. But the reports about the relationship of nutrition and immune ability and resistance to hypoxia were not seen. The object of this study is to research the effect of hypoxia on the immunological and physiological ability in the juvenile Chinese mitten crab (Eriocheir sinensis); the effect of dietary DHA and ARA on immunological and physiological ability and response to hypoxia in juvenile Chinese mitten crab (Eriocheir sinensis); the effect of dietary different DHA/EPA ratio on immunological and physiological ability and response to hypoxia in juvenile Chinese mitten crab (Eriocheir sinensis); the effect of dietary different oil lipid on immunological and physiological ability and response to hypoxia in adult Chinese mitten crab (Eriocheir sinensis). Results obtains are as follow:1,The juvenile Chinese mitten crabs Eriocheir sinensis (1.40±0.43g) were cultured in water of 2.04±0.16 (hypoxia, treatment group) and 8.01±0.22mg/L (high dissolved oxygen (DO), control group) DO for 24h, respectively. The total haemocyte counts (THC), the hyaline haemocyte counts were measured at 0 and 24 h in the treatment group, and superoxide dismutase (SOD) activity, concentrations of lactic acid and hemocyanin (Hc) in haemolymph and the metabolism of hepatopancreas (concentrations of glucose, total cholesterol, uric acid, total protein, urea, triglyceride in hepatopancreas) were assayed at 0, 2, 8 and 24 h in both treatment and control groups. The hyaline haemocyte counts and THC decreased significantly by 66% and 49% after exposure to hypoxic water for 24 h, respectively. SOD activity, Hc and lactic acid content were significantly affected in treatment group, and there were significant differences between treatment and control groups. In the treatment group the concentration of glucose, cholesterol and uric acid in hepatopancreas had a significant variation for 24 h. The concentration of total protein, urea and triglyceride between treatment and control groups was not significantly different after 0, 2, 8, 24 h. However, there were significant differences between treatment and control groups in terms of total protein, glucose and uric acid concentration. Taken together, the effect of hypoxia is comprehensive in juvenile Chinese mitten crab Eriocheir sinensis.2,The juveniles of Chinese mitten crab (Eriocheir sinensis) were raised with diets including different contents of the essential fatty acids (EFA)――docosahexaenoic acid (DHA, C22:6n-3) or arachidonic acid (ARA, C20:4n-6) for about 3.5 and 4 months, and their immunological and physiological ability after acclimated to hypoxia 24 h (DHA and ARA diet) and normal DO (dissolved oxygen) level (ARA diet) were evaluated. Five different DHA and ARA dietary preparations (group D1, D2, D3, D4, D5 and A1, A2, A3, A4, A5) were compared: 0%, 0.25%, 0.5%, 1%, 1.5% and 0%, 0.3%, 0.6%, 0.9%, 1.2% (d.w.). In DHA diet experiment the THC (total haemocyte counts), the hyaline haemocyte counts had no significant difference in five dietary groups in hypoxia water for 24 h, the hemocyanin (Hc) appeared an interesting fluctuation trend, higher supplement of DHA in diets significantly influenced the Hc content. SOD activities in supplement of DHA groups were significantly higher than 0% supplement group exposed to hypoxia for 24h. In hepatopancreas total cholesterol and triglyceride content increased with the enrichment of DHA in diets. In ARA diets experiment the immunological and physiological parameters were considerable affected by hypoxia stress. The THC and the hyaline haemocyte counts were significantly increased by the supplementation of ARA, especially in moderate supplementation (0.6%, 0.9% d.w.) in normal DO water. However, there were no differences in both SOD activity and Hc content of haemolymph among dietary treatments in normal and low DO level respectively. The LD and UA content of haemolymph in moderate supplementation ARA (0.6%, 0.9% d.w.) were significantly different with the no supplementation ARA in both DO level. In hepatopancreas the immunological and physiological ability had no difference among the dietary groups in low DO water. Thus, the hypoxia had a considerable negative impact on the immunological and physiological parameters of crabs. Enriching DHA in diets has significant improved the nutrition, physiological ability and adaptation to hypoxia stress in juveniles of E. sinensis. And the results from ARA experiment suggested that dietary ARA, especially moderate ARA level (0.6%, 0.9% d.w.), significantly improved immune and physiological response and the anti-hypoxia ability of Chinese mitten crab juveniles.3,The juveniles of Chinese mitten crab (Eriocheir sinensis) (1.32-1.76g) were raised with diets with different DHA/EPA ratios (docosahexaenoic acid (DHA, 22:6n-6); eicosapentaenoic acid (EPA, 20:5n-3)) for 3 months, and their immunological and physiological variables after acclimated to hypoxia (2.34±0.30mg/L) 24 h and at normal DO (DO: dissolved oxygen; 8.02±0.35mg/L) water were measured. Five different DHA/EPA ratio dietary preparations (group 1, 2, 3, 4, 5) were compared: 0.3, 0.6, 1, 2, 3. We found the immunological ability in haemolymph was not significantly affected by the different DHA/EPA ratio diet except the Hc content after exposure to 24 h hypoxia and the activity ofγ-GGT (γ-glutamyltransferase) at normal DO level. The antioxidase activity SOD showed a decreasing trend from diet 1 to 5 at normal DO level but there were no significant difference in the five diets after exposure to 24 h hypoxia. In haemolymph, the physiological metabolism indices were evidently affected by the different dietary DHA/EPA ratio, especially the activity of LDH (lactate dehydrogenase) in diet 4 was significant higher than other diet groups'after exposure to 24 h hypoxia. Moreover, hypoxia significantly influenced the most immunological and physiological indices. In hepatopancreas, the activity ofγ-GGT and Glu (glucose) content in diet 4 were distinctly higher than other diet groups, and the content of LD (lactic acid) in diet 3 was the highest in the five diets after exposure 24h hypoxia. Thus, feeding diet 3 and 4 was better for the immune ability, transport oxygen and metabolism physiology of intermolt juveniles of E. sinensis after exposure to 24 h hypoxia.4,The objective of this study is to measure the effect of supplement of fish and soybean oil in diets on the weight, immune, metabolism and resistance to hypoxia in Chinese mitten crab (E.sinensis). The three diets for adult crabs with different ratio fish oil and soybean oil were prepared. These diets were fed crab for 115 days. Their weight changes were measured. And then the crabs were placed into hypoxia water (2.57±0.44mg/L) and normal DO level (9.06±0.06mg/L) for 90 hours,after that their immune and metabolic indices were measured. We found that the hypoxia stress influence the metabolism of crab in some ways. The weights of crab were not significantly affected by the variety of oil lipid in diets; the supplement of fish and soybean oil (1:1) in diets evidently improved the crabs'immune and antioxidant ability, comparing with other two groups, the crabs in mix oil group had a better ability of resistance to hypoxia.The above results demonstrated that hypoxia significantly influenced the immunity and physiological ability in the juvenile of Chinese mitten crab; the supplement of DHA in diets improved the immunity system of juvenile crabs, the proper supplement of ARA (0.6, 0.9%) in diets would enhance the immunity and physiological ability of juvenile crabs; when the DHA/EPA in diets is 1 and 2, the juvenile crabs'immunity and resistance to hypoxia is better; and last, the supplement of fish oil and soy oil (1:1) in diets is better for the immunity and resistance to hypoxia in adult crabs.