Evaluation of two probiotics used during farm production of white shrimp Litopenaeus vannamei (Crustacea: Decapoda)

This study examined the effects of Bacillus licheniformis strain CIGBC‐232, isolated from the gut of shrimp Litopenaeus vannamei and having antagonistic activity against Vibrio harveyi, on the immunity and larval quality of L. vannamei at various ontogenetic stages, in two separate experiments: (1) PL2 to PL17 exposed to the strain CIGBC‐232 under laboratory conditions (2) zoea I to PL8 exposed to the strain CIGBC‐232 and EPICIN 3W probiotics under farming conditions. The first experiment showed that phenoloxidase, peroxidase and superoxide dismutase activities were improved in animals grown with CIGBC‐232 compared to the untreated control. In tests, the resistance to osmotic stress was also enhanced. During the second experiment, animals treated with CIGBC‐232 exhibited significant (P < 0.05) increases in phenoloxidase activity (30–40% higher in zoea I–II, mysis II–III and PL 2–7) and in the respiratory burst (30% higher from PL 2 to 7) as compared to those animals that received EPICIN 3W. There was no significant difference in the lectins and agglutinins (except in PL1, 6 and 7), in peroxidase and superoxide dismutase activities, in the resistance to osmotic stress, nor in the survival rate among treatments. CIGBC‐232 treatment was able to reduce, the level of presumptive Vibrio spp. with respect to EPICIN 3W treatment in the tank water as well as in animals. At the end of both experiments, the growth of shrimp, i.e. weight and length was increased by CIGBC‐232 treatment. This study showed the probiotic effect of CIGBC‐232, which appeared to have a better probiotic performance than EPICIN 3W treatment.     

Comparison of immune responses and antioxidant status of different generations of growth‐selected Portunus trituberculatus families

The purpose of this study was to investigate the effects of inbreeding on the immune responses and antioxidant status of Portunus trituberculatus juveniles. Results showed that inbreeding affected the total haemocyte count, and phagocytic, pro‐phenoloxidase (propo), phenoloxidase and antibacterial activities decreased after the seventh generation. Antioxidant status showed a similar pattern: total antioxidant capacity, superoxide dismutase (SOD) activity and GSH/GSSG in the cell‐free haemolymph and hepatopancreas decreased, while catalase activity in the cell‐free haemolymph increased (P < 0.05). There were no significant differences in α₂‐macroglobulin and bacteriolytic activities in the cell‐free haemolymph and glutathione peroxidase activity in the cell‐free haemolymph and hepatopancreas among nine inbreeding generations. Gene expression levels of proPO and crustin in haemocytes and SOD in haemocytes and hepatopancreas also decreased significantly as the inbreeding generations increased. The results suggest that a high level of inbreeding could severely reduce the physiological health of P. trituberculatus. Our obtained data would be particularly useful for P. trituberculatus breeding programmes.     

Effects of hypoxia on immune responses and carbohydrate metabolism in the Chinese mitten crab,Eriocheir sinensis

In aquaculture, hypoxia is an important stressor that can inhibit the healthy development of Chinese mitten crab, Eriocheir sinensis. The aim of this work was to research on how hypoxia (1 mg/L) followed by reoxygenation affects the immune response and carbohydrate metabolism in the Chinese mitten crab. The activities of immune‐related enzymes including lysozyme (LZM), acid phosphatase (ACP), alkaline phosphatase (AKP), superoxide dismutase (SOD) and phenoloxidase (PO) and concentration changes in haemolymph glucose, trehalose and hepatic glycogen were evaluated after 8 hr of hypoxia followed by 12 hr of reoxygenation. After 8 hr of hypoxia, the activities of LZM, PO, SOD and hepatic glycogen concentration significantly decreased to the minimum when compared to the control group, but the activities of ACP and AKP, and haemolymph glucose concentration significantly increased. After 12 hr of reoxygenation, the activities of LZM, ACP, AKP and SOD recovered to the normal level except SOD in plasma, while the PO, SOD in plasma and hepatic glycogen concentration were still significantly lower than the control level. No significant change was observed in trehalose concentration during hypoxia and reoxygenation periods. These results indicated that although the activities of ACP and AKP were likely increased to facilitate the hydrolysis of foreign matter, the overall strength of the immune response was decreased as LZM, PO and SOD activities were suppressed after exposure to hypoxic conditions. The energy stores of exposed crabs were reduced due to the expenditure of energy during exposure to hypoxic stress. In general, chronic hypoxia would impair the immunocompetence and increase the energy expenditure of Chinese mitten crab, further increased the risk of pathogen infection and feed coefficient, so the negative effects of hypoxia should not be ignored.     

Effect of dietary encapsulated organic salts (Na‐acetate,Na‐butyrate,Na‐lactate and Na‐propionate) on growth performance,haemolymph, antioxidant and digestive enzyme activities and gut microbiota of juvenile narrow clawed crayfish,Astacus leptodactylus leptodactylus Eschscholtz, 1823

A 63‐day experiment was done to study the effects of four levels (5, 10, 20 and 50 g/kg) of encapsulated organic salts (Na‐acetate, Na‐butyrate, Na‐lactate and Na‐propionate) on the growth indices and haemato‐immunological responses of crayfish Astacus leptodactylus leptodactylus (4.38 ± 0.08 g). Crayfish were distributed at 51 1,000‐L tanks (17 treatments at triplicate). The highest values of final weight (27.86 g), specific growth rate (2.94% body weight per day) and survival rate (96%) were observed in the crayfish fed the 20 g/kg of encapsulated Na‐propionate diet (p < .05). The highest activities of phenoloxidase (7.4 U/min), superoxide dismutase (7.80 U/min) and lysozyme (9.40 U/min) were observed in the gut of crayfish fed the 20 g/kg of encapsulated Na‐propionate diet (p < .05), as well as the highest activities of alkaline protease (10.70 U/mg), lipase (9.10 U/mg), amylase (9.60 U/mg) and the lactobacillus count (p < .05). Broken line regression model of SGR and phenoloxidase activity suggested that the optimum dietary levels of encapsulated Na‐acetate, Na‐butyrate, Na‐lactate and Na‐propionate could be 30.7, 31.8, 31.4 and 33.5 g/kg, respectively, in crayfish reared in culture conditions.     

Effects of dietary astaxanthin on growth,antioxidant capacity and gene expression in Pacific white shrimp Litopenaeus vannamei

Pacific white shrimp Litopenaeus vannamei (1050 individuals with initial weight of 1.01 ± 0.001 g) were fed either control diet or one of six dietary astaxanthin (AX) concentration (25, 50, 75, 100, 125 and 150 mg kg⁻¹) diets for 56 days in 35 tanks (30 shrimp per tank). After 56 days of culture, shrimp‐fed AX125 and AX150 diets had higher (P < 0.05) weight gain, specific growth rate, total antioxidant status and lower (P < 0.05) superoxide dismutase (SOD), catalase (CAT) than shrimp fed control diet. After low dissolved oxygen stress for 1 h, survival rate of shrimp fed AX75, AX100, AX125 and AX150 diets was higher (P < 0.05) than that of shrimp fed control diet. Hypoxia inducible factor‐1α (HIF‐1α), cytosolic manganese superoxide dismutase (cMnSOD) and CAT mRNA expression levels of shrimp fed seven diets were significantly down‐regulated under hypoxia than under normoxia, but their expression levels were higher under hypoxia in shrimp fed AX‐supplemented diets than in shrimp fed control diet. About 70‐kDa heat‐shock protein (Hsp70) mRNA expression level of shrimp fed seven diets was significantly up‐regulated under hypoxia than under normoxia, but its expression level was lower under hypoxia in shrimp fed AX‐supplemented diets than in shrimp fed control diet.     

Multiple dietary administrating strategies of water hyacinth (Eichhornia crassipes) on enhancing the immune responses and disease resistance of giant freshwater prawn,Macrobrachium rosenbergii

The different products of Eichhornia crassipes leaves including dried E. crassipes powder (DEP), hot‐water treated E. crassipe (HTE), hot‐water extract of E. crassipe (ECE) and dreg of hot‐water extract of E. crassipe extract (dECE) were produced and incorporated into the diet of the prawn, Macrobrachium rosenbergii, as an immunostimulant. Results showed that prawn fed the HTE‐, ECE‐ and dECE‐containing diets for 4 months had increased total haemocyte count, different haemocyte count, phenoloxidase activity, respiratory bursts, superoxide dismutase activity, glutathione peroxidase activity especially in HTE and ECE treatments. The phagocytic activity and clearance efficiency against Lactococcus garvieae of prawn fed the HTE‐ and ECE‐containing diets were significantly higher than those of prawn fed the control diet at 2–4 months. The relative percentage survival of prawn fed the DEP‐, HTE‐, ECE‐ and dECE‐containing diets for 4 months following 144 h challenging with L. garvieae were 19.0%, 38.1%, 38.1% and 33.3%. It was concluded that E. crassipes leaves containing an active component which was easily extracted by hot water can enhance innate immunity and resistance against pathogen of M. rosenbergii by dietary long‐term administration, and the administration of HTE in the diet was the best strategy due to the availability and convenience.     

Immune responses by dietary supplement with Astragalus polysaccharides in the Pacific white shrimp,Litopenaeus vannamei

Two experiments were conducted to investigate the immune‐enhancing effect of dietary supplement with Astragalus polysaccharides (APS) on the Pacific white shrimp, Litopenaeus vannamei. In experiment 1, the optimal APS dose was determined based on the immune responses of shrimps fed APS diet for 30 days. In experiment 2, the effect of APS supplementation on immune response of shrimp suffering white spot syndrome virus (WSSV) challenge was determined. Results showed that the total haemocyte count and phagocytic activity in shrimps fed APS diets significantly (p < .05) increased in comparison with those fed the basal diet. Dietary supplement with APS markedly (p < .05) increased the activity of phenoloxidase (PO), total superoxide dismutase (SOD), lysozyme (LZM), acid phosphatase and alkaline phosphatase in shrimp hemolymph, but decreased the maleic dialdehyde (MDA) content. Significantly higher (p < .05) activity on PO, SOD and LZM and lower (p < .05) MDA content have also been found in shrimps suffering WSSV challenge. Therefore, APS could be used as a safe and effective feed additive in shrimp aquaculture, and the optimal dose of APS for the Pacific white shrimp was suggested to be 0.2 g/kg based on our results.     

Seasonal variations of immune parameters in the coelomic fluid of sea cucumber Apostichopus japonicus cultured in pond

In order to understand the effects of seasonal change on the immunity of sea cucumber Apostichopus japonicus cultured in pond, A. japonicus with body weight of 12.2 ± 4.5 g (sample A) and 32.6 ± 7.1 g (sample B), respectively, were collected monthly and randomly from a typical pond during a year cycle and employed for the evaluation of immunocompetence. Simultaneously, the environmental factors in the pond including water temperature, pH, salinity and dissolved oxygen (DO) were measured using a handheld multiparameter meter. The activities of acid phosphatase (ACP), alkaline phosphatase (ALP), lysozyme (LYZ), phenoloxidase (PO), superoxide dismutase (SOD), catalase (CAT) and myeloperoxidase (MPO) in the coelomic fluid were selected for the evaluation of A. japonicus immunocompetence and determined using biochemical methods. The results showed that in both samples, the activities of all determined enzymes had small values in winter and early spring, and LYZ, CAT and MPO activities also presented small values in summer, suggesting that pond‐cultured A. japonicus underwent immunosuppression twice during a year cycle, and the immunosuppression occurred in winter and early spring was more severe than that occurred in summer. In addition, most of the determined enzymes showed different variations between the two samples, and had significantly negative correlation with protein concentration, which was significantly and negatively correlated with water temperature, revealing that body weight and water temperature might have crucial effects on the immunity of A. japonicus cultured in pond.     

Effect of hypoxia on immunological,physiological response,and hepatopancreatic metabolism of juvenile Chinese mitten crab <Emphasis Type="Italic">Eriocheir sinensis</Emphasis>

The juvenile Chinese mitten crabs Eriocheir sinensis (1.40 ± 0.43 g) were cultured in water of 5.34 ± 0.43 (hypoxia, treatment group) and 21.02 ± 0.06 kPa (high dissolved oxygen (DO), control group) DO for 24 h, respectively. The total hemocyte counts (THC), the hyaline hemocyte 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 hemolymph 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 hemocyte 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.     

Effects of polysaccharides from mycelia of Cordyceps sinensis on growth performance,immunity and antioxidant indicators of the white shrimp Litopenaeus vannamei

Studies were conducted to evaluate polysaccharides from mycelia of Cordyceps sinensis (PMCS) as a feed additive for pacific white shrimp (Litopenaeus vannamei). Shrimps were randomly divided into two groups. One group received the PMCS‐supplemented diet for 52 days, and the other group received no treatment. The data showed that shrimps given PMCS gained more body weight compared with the control group (P < 0.05). Haemolymph immunity indicators, including phenoloxidase (PO), alkaline phosphatase (ALP), acid phosphatase (ACP) and lysozyme (LSZ), were remarkably greater in the PMCS group (P < 0.05). In addition, antioxidant parameters, including superoxide dismutase (SOD), glutathione reduced form (GSH), reactive oxygen species (ROS) and total antioxidant capacity (TAC), were significantly greater in the treatment group. However, there were no significant differences in malondialdehyde (MDA) levels and glutathione peroxidase (GSH‐PX) activity between the control and treatment groups. Moreover, the number of Vibrio ichthyoenteri was less in the group treated with PMCS (P < 0.05). In conclusion, PMCS can be used to improve the growth performance and health of pacific white shrimp.     

Evaluating the effects of dietary resistant starch on growth,digestion, metabolism,immunity and resistance to ammonia stress in Litopenaeus vannamei

Resistant starch (RS) is considered to be a good alternative to antibiotics. A 56‐day feeding trial was followed by induction of acute ammonia stress to evaluate the effects of dietary RS on growth, digestion, metabolism, immunity and resistance to ammonia stress in Litopenaeus vannamei. The four diets used differed only in RS content: 0 g/kg (Control), 10 g/kg (RS1), 30 g/kg (RS2) and 50 g/kg (RS3). The results showed that dietary RS improved the growth and the survival rates of shrimp exposed to ammonia stress. At 56 days, the activity of digestive and metabolic enzymes (amylase, lipase, pepsin, hexokinase and pyruvate kinase) was increased in the three RS groups, while trypsin activity only increased in the RS1 and RS2 groups; immune‐related parameters (the total antioxidant capacity; the activity of superoxide dismutase, total nitric oxide synthase and phenoloxidase; and the expression of heat‐shock protein 70, thioredoxin, prophenoloxidase, lysozyme and toll gene) were increased in the three RS groups. After exposure to ammonia stress, all the selected immune parameters of the three RS groups were higher than those of the control group at 24 hr. Therefore, dietary RS improved the growth, digestion, metabolism, immunity and resistance to ammonia stress in L. vannamei.     

Simplified processing method of banana (Musa acuminata) peels possess the improvement in immunological responses of Macrobrachium rosenbergii

Musa acuminate peel extract as an immunostimulant, administrated in the diets of Macrobrachium rosenbergii, and an assessment of a simplified process to develop low‐cost feed additives are conducted in this study. The products obtained serially, during the processes of hot‐water banana peel extraction, were administrated in the diets of M. rosenbergii, including dried banana peel powder (DBP) at 8 g/kg, hot‐water‐treated banana peel (HBP) at 8 g/kg and hot‐water extract of banana peel (BPE) at 2 g/kg during the 32 days of the feeding trial. Total haemocyte count, different haemocyte count, respiratory bursts; and activity of superoxide dismutase, glutathione peroxidase, phenoloxidase and transglutaminase, as well as an accelerated haemolymph clotting time, significantly increased in M. rosenbergii fed with diets containing HBP and BPE, 32 days post‐feeding. Furthermore, the phagocytic activity and clearance efficiency of prawns against Lactococcus garvieae infection increased significantly. The respective relative survival percentages of prawns fed with HBP, and BPE containing diets after 32 days of feeding trial were 29.2% and 41.7% against L. garvieae infection for 144 hours, and 50%, and 50% against hypothermal stress for 96 hours of exposure. We may therefore conclude that HBP, obtained from a simplified procedure, without centrifugation and lyophilization, may strategically promote tolerance to hypothermal stress, and enhance immunity and resistance to L. garvieae infection.     

Long-term mild hypoxia does not reduce thermal tolerance or performance of the freshwater prawn Macrobrachium tenellum

The present study was designed to assess the performance of the freshwater prawn Macrobrachium tenellum in optimal and sub-optimal dissolved oxygen conditions, considering increasing environmental pressures. Thermal tolerance and thermal metabolic scope (TMS) with related integrated biomarker response (IBR) were measured in prawns exposed to normoxia (80% air saturation), mild (40% air saturation) and severe hypoxia (25% air saturation) at three exposure time points (10, 20 and 30 days). Effects of hypoxia on thermal tolerance were not detectable over time; they were perhaps masked by hyperventilation, or by an increase or diversion of haemolymph processes. After 30 days, TMS was 11% higher in mild hypoxia compared with normoxia, while it was 64% lower in severe hypoxia, indicating the loss of aerobic metabolism capacity during the latter. Mild-hypoxia prawns maintained a high IBR over time, supported by antioxidant enzyme activities (mainly superoxide dismutase), which helped avoid the serious oxidative damage (proteins and lipids) seen in severe hypoxia animals, as well as lower acetylcholinesterase activity that indicated failure of communication between the nervous and locomotor systems. Our results documented a high tolerance by M. tenellum to mild-hypoxia events, which should be further tested under seasonal and extreme habitat/tank temperatures.     

Dietary butyric acid improved growth,digestive enzyme activities and humoral immune parameters in Barramundi (Lates calcarifer)

A six‐week feeding trial was conducted to determine the effect of butyric acid (BA) inclusion in diet on performance of Barramundi (Lates calcarifer). Fish (12.0 ± 0.2 g) were fed with four experimental diets contained 0.0 (control), 2.5, 5.0 and 10.0 g BA/kg in triplicate. Fish fed on 5 and 10 g BA/kg diets had higher growth and total alkaline protease and lipase activities than the other treatments. Fillet protein content in BA‐supplemented groups was higher than the control. Liver catalase activity was highest in 2.5 g BA/kg group compared with the other groups. The values of liver superoxide dismutase activity and serum total protein concentration in 5 and 10 g BA/kg treatments were higher than those in the control (p < .05). Moreover, the highest and the lowest levels of serum lysozyme activity were noticed in the 10 g BA/kg and the control groups, respectively (p < .05). Also, the highest respiratory burst activity was observed in fish fed 5 g BA/kg feed. Supplementing diet with 2.5 or 5 g BA/kg resulted in higher serum haemolytic activity in fish compared with the other groups. The number of red and white blood cells increased in fish fed BA‐supplemented diets compared with the control (p < .05). In conclusion, the results of this study showed inclusion of BA at 5 g/kg diet in L. calcarifer juveniles improved growth and upgraded the general health condition by enhancing fish antioxidant enzyme activities and haemato‐immunological responses.     

Dietary nano‐selenium enhances antioxidant capacity and hypoxia tolerance of grass carp Ctenopharyngodon idella fed with high‐fat diet

To evaluate the effects of dietary nano‐selenium (Nano‐Se) on antioxidant capacity and hypoxia tolerance of grass carp fed with high‐fat diet, experimental fishes were fed Nano‐Se supplemented diets at doses of 0 (Control), 0.3, 0.6, 0.9 and 1.2 mg/kg for 10 weeks. After feeding trial, a part of the fishes were exposed to hypoxia stress. Results showed that the survival ratio of grass carp significantly increased in 0.6 and 0.9 mg/kg Nano‐Se group, and the content of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) significantly decreased in 0.6–1.2 mg/kg Nano‐Se groups compared with the control group. In addition, dietary Nano‐Se significantly enhanced glutathione peroxidase (GPX) activity and reduced the malondialdehyde (MDA) content in fishes fed diets with 0.3 and 0.6 mg/kg Nano‐Se. Dietary Nano‐Se significantly elevated mRNA expression of GPX1 and catalase (CAT) by promoting the mRNA expression of NF‐E2‐related nuclear factor 2 (Nrf2) in the hepatopancreas. After hypoxia stress, the GPX and superoxide dismutase (SOD) activities were significantly enhanced, and the MDA content and mortality rate consequently decreased in fishes fed diets with 0.3 and 0.6 mg/kg Nano‐Se. In summary, these results suggested that optimal Nano‐Se in diet enhanced the antioxidant capacity and hypoxia tolerance of grass carp.     

Growth performance,haematology, antioxidant status,immune response and histology of common carp (Cyprinus carpio L.) fed biofloc grown on different carbon sources

A 10 weeks trial was performed to investigate how different carbon sources (sugar beet molasses: SBM+BFT, sugar: S+BFT, corn starch: CS+BFT) along with control affect welfare status of common carp (Cyprinus carpio L.) fingerlings in biofloc‐based tanks. Three hundred healthy fingerlings (22.5 ± 0.2 g) were randomly distributed in 12 tanks (70 L) at a density of 8.02 kg/m³ (25 fish/tank). The fish in BFT treatments fed only 75% feeding rate of control. At the end of the experiment no differences were seen between the groups in case of growth performance, but the fish reared in CS+BFT had a significant lower food conversion ratio compared with the others (p < .05). Different carbon sources did not affect on haematological parameters (p > .05). Total serum protein and antibody concentration differed in treatments, and the highest values were found in S+BFT and CS+BFT treatments (p < .05). No significant differences were observed in case of lysozyme, superoxide dismutase and complement activity in treatments (p > .05), whereas the fish in BFT treatments showed a significant higher total antioxidant capacity and lower glutathione peroxidase than the control (p < .05). Different carbon sources resulted in no change in goblet and kupffer cells in intestine and liver respectively. The highest relative percentage survival was obtained in the CS+BFT and S+BFT (50%) in comparison with SBM+BFT (20%) treatment. The results obtained in this experiment, suggest that corn starch improves immune response, diseases resistance and histology of digestive and respiratory systems in carp fingerlings when used as a carbon source in zero water exchange system.     

Dietary administration of soybean isoflavones enhances the immunity of white shrimp Litopenaeus vannamei and its resistance against Vibrio alginolyticus

The growth response, total hemocyte count (THC), respiratory burst (release of superoxide anion), phenoloxidase (PO) activity, superoxide dismutase (SOD) activity, nitric oxide synthase (NOS) activity and resistance to the pathogen Vibrio alginolyticus were measured in white shrimp (Litopenaeus vannamei) which had been fed diets supplemented with soybean isoflavones (SI) at 0, 5, 10, 20, 40 mg kg^?1 feed for 8 weeks. Dietary SI had no significant influence on survival rate of the shrimp. Significantly greater SGR was observed in treatments with 10, 20 and 40 mg kg^?1 SI supplement than that in control (P < 0.05). Shrimp fed a diet with 20 mg kg^?1 SI showed significant increase in THC, PO activity, respiratory burst activity, SOD activity as well as NOS activity (P < 0.05). Increased THC, respiratory burst activity, SOD activity and NOS activity were also noticed in shrimp fed SI at 10 or 40 mg kg^?1 (P < 0.05). Significant lower cumulative mortality after challenge was observed in shrimp fed diets with SI supplement (10.0–13.3%) than that in control group (36.7%) (P < 0.05). It is therefore concluded that oral administration of SI at 20 mg kg^?1 for 8 weeks could enhance the immune ability of shrimp and improve production in shrimp farming.     

Aluminum-induced oxidative stress in lymphocytes of common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis>)

Several studies of fish have shown that aluminum may induce hypoxia, hypercapnia, metabolic acidosis, and respiratory failure. In lymphocytes, morphologic abnormalities and reduced immune activity have been observed. Nevertheless, there is little data on oxidative stress and such data are essential in order to identify its mechanism of action. The common carp Cyprinus carpio, an omnivorous fish commonly used in commercial aquaculture, has been proposed as a test organism in toxicologic assays due to its economic importance and wide geographic distribution. The aim of this work was to evaluate Al-induced oxidative stress in lymphocytes of the common carp C. carpio. Specimens were exposed to three different concentrations of Al (0.05, 120, and 239 mg/l) in a static exposure system for 96 h. At the end of the exposure period, blood was collected and lymphocytes were separated. Lipid peroxidation, oxidized protein content and the activity of superoxide dismutase, catalase, and glutathione peroxidase were measured. Results show that the tested Al concentrations modified the activity of antioxidant enzymes and elicited higher levels of lipid peroxidation and oxidized proteins. The degree of damage induced was concentration and tissue dependent.     

Effect of biofloc technology on water quality and feed utilization in the cultivation of gibel carp (Carassius auratus gibelio var. CAS III)

This study was designed to use sucrose as carbon source to investigate the effect of biofloc technology on water quality and feed utilization in the cultivation of gibel carp (Carassius auratus gibelio var. CAS III). Three isolipidic and isoenergetic diets were formulated containing graded levels of dietary protein (257.4, 300.7 and 353.4 g/kg). The control group (P34) was fed with 353.4 g/kg protein diet without biofloc. Three biofloc treatments (P24 + B, P29 + B and P34 + B) were fed with the three diets with daily sucrose supplementation and continuous air inflation. The results found that the sucrose supplementation could generate biofloc and increased biofloc volume (BFV, p < 0.05). The concentration of total ammonia nitrogen (TAN), nitrate nitrogen (NO₃‐N) and the total phosphorus (TP) of all tanks decreased in biofloc groups, and the total nitrogen (TN) of P24 + B treatment tanks was significantly lower than that of the control group (p < 0.05). The growth of P24 + B and P29 + B group was similar with that of control group (p > 0.05). Feed conversion ratio (FCR) of P29 + B was lower than P24 + B and P34 + B (p < 0.05). Protein retention efficiency (PRE) of P24 + B group was significantly higher than other treatments (p < 0.05). Phosphorus retention efficiency (PhRE) of P24 + B group was the highest among all treatments. Compared with the control group, P29 + B group had an improved total antioxidant capacity (T‐AOC), superoxide dismutase (SOD) activity and contained the lowest malondialdehyde level (MDA). The present results indicated that low‐protein diet is more suitable for gibel carp in zero‐water exchange biofloc system compared with high‐protein diet.     

Effect of saponin on hematological and immunological parameters of the giant freshwater prawn, Macrobrachium rosenbergii

Giant freshwater prawns, Macrobrachium rosenbergii (17.9 ± 2.7 g), exposed to different concentrations of saponin at 0, 0.3, 0.6, 0.9 and 1.2 mg l^− 1 for 168 h were examined for osmolality, electrolyte levels, oxyhemocyanin, protein levels, acid-base balance status, total hemocyte count (THC), phenoloxidase activity, and respiratory bursts. Hemolymph oxyhemocyanin, protein, and pO₂ were inversely related to the saponin concentration. Hemolymph oxyhemocyanin, protein, pO₂, pCO₂, and pH of prawns exposed to 1.2 mg l^− 1 saponin were significantly lower than those of prawns exposed to 0.3 mg l^− 1 and control solutions. However, no significant difference was observed in osmolality or electrolyte levels of prawns exposed to different concentrations of saponin for 168 h. The THC of prawns following 168 h of exposure to 0.9 and 1.2 mg l^− 1 saponin increased, but the phenoloxidase activity decreased suggesting that the decrease in phenoloxidase activity under saponin stress was not a consequence of the increase in THC. We concluded that saponin at as low as 0.9 mg l^− 1 decreases the respiratory protein level and acid-base balance, and modulates the immune system of M. rosenbergii.