Effect of Coriolus versicolor polysaccharides on the hematological and biochemical parameters and protection against Aeromonas hydrophila in allogynogenetic crucian carp (Carassius auratus gibelio)

The effect of dietary intake of Coriolus versicolor Polysaccharides (CVP) on the hematological and biochemical indices of Allogynogenetic crucian carp (Carassius auratus gibelio) was investigated. Fish were fed CVP supplemented diets (0, 0.25, 0.5, 1.0, 2.0 or 4.0 g CVP kg^?1) for 56 days. The RBC, WBC counts, hemoglobin content, ESR in blood and TP, ALT, AST, ALP, GLU, CHO, TG, and BUN in serum were measured on day 0, 14, 28, 42, and 56. After feeding of 56 days, fish were infected with Aeromonas hydrophila and mortalities were recorded. The results indicated that feeding crucian carp with suitable dose of CVP enhanced the RBC, WBC counts, hemoglobin and TP content, ALP activity, and decreased the ESR, ALT, AST, GLU, CHO, TG and BUN. There was no effect in fish at low dose (0.25 g kg^?1). Unexpectedly, the higher CVP dose used here (2.0 and 4.0 g kg^?1) has a negative effect in fish. The results of challenge experiment indicated that a moderate level of CVP in the diet (1.0 g kg^?1) was the most effective to enhance the survival of fish after infected with A. hydrophila. In summary, the use of CVP, as dietary supplements, can improve the innate defense of crucian carp providing resistance to pathogens.     

Extracts of Oliviera decumbens and Satureja khuzestanica as immunostimulants affect some innate immunity indices of Cyprinus carpio against Aeromonas hydrophila infection

In this study, the effect of extracts of two herbs (Oliviera decumbens and Satureja khuzestanica) on immune response of carp was investigated. At the beginning of experiment, fish were divided to two groups including vaccinated (using vaccine developed against A. hydrophila) and non‐vaccinated. Fish in both groups were fed diets containing O. decumbens and S. khuzestanica and combination of two herbal extracts for 5 weeks. Control fish (negative control) and fish vaccinated only (positive control) were fed basal diets without supplements of herbal extracts. Lysozyme activity, antibody titre, complement activity and bactericidal activity in serum were measured. After 5 weeks feeding, fish were infected with A. hydrophila and mortalities were recorded. In both experimental groups, no significant differences were found in terms of alternative haemolytic complement (ACH50) activity and antibody titres of Serum. In non‐vaccinated fish group, lysozyme and bactericidal activity of fish fed S. khuzestanica or combination of O. decumbens and S. khuzestanica was higher compared with control and other experimental treatments. In vaccinated fish group, the lysozyme and bactericidal activity was not significant in all treatments compared with control group. The results of this study showed that feeding non‐vaccinated and vaccinated carp with only S. khuzestanica or in combination with O. decumbens enhance only some immunity indices including lysozyme and bactericidal activity in non‐vaccinated fish and these extracts have no immunological stimulatory role on vaccinated individuals.     

Ammonia nitrogen excretion in Mandarin Fish (Siniperca chuatsi) and Grass Carp (Ctenopharyngodon idellus) fed practical diets: the effects of water temperature

To understand the actual production of fish culture about the utilization of dietary protein and excreta impact on the environment between mandarin fish (Siniperca chuatsi) and grass carp (Ctenopharyngodon idellus), the study to investigate the effect of temperatures (19 ± 0.5°C, 24 ± 0.5°C and 29 ± 0.5°C) on ammonia‐N excretion in mandarin fish and grass carp under fed and fasted states was conducted. These two species were fed a practical diet containing 325.2 g kg^?1 crude protein at 3% body weight per day. The ammonia‐N excretion rate was significantly increased when temperature increased from 19 to 29°C, and a linear relationship between ammonia‐N excretion rate and temperature. The maximum ammonia‐N excretion levels of mandarin fish and grass carp were observed at 4–8 h and 2–4 h after feeding, respectively, and the minimum values for both species were observed at 24 h after feeding. Under the feeding condition, mandarin fish had a lower ammonia‐N excretion level compared to grass carp at 24°C and 29°C. The average amount of ammonia‐N excreted by mandarin fish at 24 h is significantly higher than grass carp under fasting conditions, except 19 ± 0.5°C. These results indicated that mandarin fish might make better use of protein at higher temperature than grass carp when fed practical diets in commercial production. These results of this study suggested that mandarin fish had a lower ammonia‐N excretion level compared with grass carp, making a less contribution to environmental loading in an intensive fish culture.     

Immunogene expression in head kidney and spleen of common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.) following thermal stress and challenge with Gram-negative bacterium, <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>

To evaluate the effect of thermal and microbial stress on the immune response of common carp (Cyprinus carpio L.), relative mRNA expression level of pro-inflammatory cytokines [tumor necrosis factor alpha (TNF-α) and interleukin (IL)-1β] and other genes related to immune or stress response [inducible nitric oxide synthase (iNOS), heat shock protein 70 (Hsp70), superoxide dismutase one (SOD1), and glucocorticoid receptor (GR)] was measured by quantitative PCR (qPCR). In addition, total protein and total immunoglobulin level in blood plasma of experimental common carp was also assayed. All the above parameters were estimated 24 h post-challenge with Gram-negative bacterium, Aeromonas hydrophila. Common carp (54.89?±?6.90 g) were initially exposed to 20 °C (control group) and 30 °C (thermal stress group) water temperature for 30 days, followed by experimental challenge with 2.29?×?10⁸ colony forming unit/mL (CFU/mL; LD₅₀ dose) of A. hydrophila. Exposure of fish to thermal stress and subsequently challenge with A. hydrophila significantly (P?<?0.05) increases the IL-1β mRNA expression in head kidney and spleen of common carp by ~?39.94 and ~?4.11-fold, respectively. However, TNF-α mRNA expression in spleen decreased ~?5.63-fold in control fish challenged with A. hydrophila. Thermal stress and challenge with bacterium suppresses the iNOS and GR mRNA expression in spleen of common carp. Moreover, significant (P?<?0.05) increase in total protein content of blood plasma (~?43 mg/g) was evident in fish exposed to thermal stress and challenged with A. hydrophila. In conclusion, our study highlights the importance of elevated temperature stress and microbial infection in differential regulation of expression of several immunogenes in common carp.     

Regulation of adipocytes lipolysis by n-3 HUFA in grass carp (Ctenopharyngodon idellus) in vitro and in vivo

N-3 highly unsaturated fatty acids (n-3 HUFA) have been shown to inhibit body fat accumulation in animals. To clarify the mechanism of this fat-lowering effect of n-3 HUFA in grass carp (Ctenopharyngodon idellus), two experiments were conducted. In experiment 1, isolated grass carp mature adipocytes were incubated with docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) at different concentrations for 6 h. The release of glycerol to the medium was detected, and the expression of the lipolysis-related genes was analyzed. In experiment 2, a 95-day feeding trial was conducted with two diets formulated with either lard oil (as control) or fish oil (supplying n-3 HUFA as treatment) as the main lipid source. The glycerol and free fatty acid (FFA) released from the isolated adipocytes of both groups were detected after the feeding period. The expression of select lipolysis-related genes in adipose tissue was also analyzed. The results from experiment 1 showed that the release of glycerol was significantly increased by DHA and EPA (P < 0.05). Moreover, the expression of lipolysis-related genes, such as adipose triglyceride lipase (ATGL), hormone-sensitive lipase (HSL), tumor necrosis factor α (TNFα) and leptin, was also significantly elevated in the treatment group (P < 0.05). Experiment 2 demonstrated that glycerol and FFA release from the isolated adipocytes were significantly higher in the treatment group compared to the control group (P < 0.05). The expression level of ATGL, HSL, TNFα and leptin in the treatment group was significantly higher than in the control group (P < 0.05). The present results provide novel evidence that n-3 HUFAs could regulate grass carp adipocyte lipolysis in vitro or in vivo, and the effect might be in part associated with their influence on the expression of lipolysis-related genes and lipolysis-related adipokines genes.     

Dietary taurine can improve the hypoxia-tolerance but not the growth performance in juvenile grass carp Ctenopharyngodon idellus

This study was conducted to evaluate the effects of dietary taurine, as a feed additive, on the hypoxia-tolerance and growth performance of the juvenile grass carp Ctenopharyngodon idellus, one of the most important and intensively cultured freshwater fish, with the largest production in China. Graded levels of taurine (0, 0.5, 1, 1.5, 2 and 2.5 g kg^–1 dry diet) were fed to grass carp juveniles (mean weight: 5.26 ± 0.03 g) for 8 weeks. The survival time during acute hypoxia increased as dietary levels of taurine increased, with the highest dose of taurine resulting in the best acute hypoxia-tolerance. The erythrocyte osmotic fragility in grass carp was significantly improved when dietary taurine level was at least 1.5 g kg^?1 diet and can be improved much more when dietary taurine level was up to 2.5 g kg^?1 diet. A significant correlation between hemolysis rate of the erythrocyte osmotic fragility test and the survival time of acute hypoxia (r = ?0.873, P = 0.023 < 0.05) strongly suggested that the biomembrane stabilization function of taurine may contribute to its role of enhancing acute hypoxia-tolerance in grass carp. Dietary taurine cannot improve growth performance of grass carp, but it can increase the value of mesenteric fat index, indicating that dietary taurine influences the lipid metabolism. This study provides valuable information to improve hypoxia-tolerance of grass carp.     

A study of the damage of the intestinal mucosa barrier structure and function of <Emphasis Type="Italic">Ctenopharyngodon idella</Emphasis> with <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>

The aim of this study is to explore the effect of Aeromonas hydrophila on the intestinal mucosal barrier structure and intestinal permeability in grass carp (Ctenopharyngodon idella). Histopathological examinations showed that A. hydrophila induced severe intestinal lesions, including inflammatory cell infiltration and intestinal villus fusion and swelling. Messenger RNA (mRNA) expression of the inflammatory cytokines TNF-α, IL-1β, IL-8, IL-10 and MyD88 was significantly increased after infection with A. hydrophila. The permeability of intestinal mucosa was determined using Evans blue (EB) and d-lactic acid. The results indicated that the levels of EB and serum d-lactic acid were significantly increased after infection with A. hydrophila (p < 0.05). Our results also indicated that the intestinal mucosal barrier injury induced by A. hydrophila infection was closely associated with the expression of the tight junction (TJ) protein zonula occludens-1 (ZO-1), occludin, claudin b and claudin c as well as the activity of Na⁺, K⁺-ATPase and Ca²⁺, Mg²⁺-ATPase. Lower mRNA levels of occludin and lower Na⁺, K⁺-ATPase and Ca²⁺, Mg²⁺-ATPase activity in the intestines were observed after challenge. ZO-1 and claudin c were significantly increased 24 h after infection with A. hydrophila. The most interesting finding was that claudin b also significantly increased 24 h after challenge and then decreased to lower levels at 72, 120 and 168 h post-infection compared to the PBS-treated control group. The results demonstrated that grass carp infection with A. hydrophila induced intestinal inflammation and impaired the structure and function of the intestinal mucosal barrier.     

The influence of feeding diets containing wheat gluten supplemented with dipeptides or free amino acids on structure and development of the skeletal muscle of carp (Cyprinus carpio)

A 28-day feeding trial was conducted to evaluate the influence of feeding diets containing plant protein wheat gluten supplemented with dipeptides or free amino acids on structure and development of the skeletal muscles of carp (Cyprinus carpio). Common carp fingerlings (1 month old) having an of average weight of 0.07 ± 0.02 g and total length of 17.79 ± 1.79 mm were fed three formulated diets—wheat gluten protein-based diets supplemented with Lys–Gly dipeptide (PP), free lysine and glycine (AA), control diet without lysine supplemented (CON)—and two other diets: restrictive diet—frozen zooplankton (Z) and commercial diet Aglo Norse (AN). After 28 days of experimental feeding, statistically significant higher survival was observed among fish fed AN and Z diets (99.5 ± 1.0 %; P ≤ 0.05). The feeding AN diet has had also a positive influence on weight and growth rate as well as on development and growth of skeletal muscles. Furthermore, carps fed AN diet had the largest area of red and white muscle as compared with the other feeding groups, and the differences were statistically significant (P ≤ 0.05). The increase in the number of proliferating cells (proliferating cell nuclear antigen) was observed on the last day of the experiment among carps fed PP, AA and CON. Moreover, fish fed PP significantly had the greatest number of MyoD- and myogenin-positive nucleus (P ≤ 0.05). Among the experimental diets based on wheat gluten, a positive impact on structure and development of muscles has been observed in carps fed PP diet.     

Molecular characterization of cholecystokinin in grass carp (Ctenopharyngodon idellus): cloning, localization, developmental profile, and effect of fasting and refeeding on expression in the brain and intestine

Cholecystokinin (CCK) is a multi-functional brain–gut peptide in fish and mammals. To investigate the role of CCK in appetite regulation in fish, a 770-bp full-length cDNA sequence of CCK gene was obtained by RT-PCR and rapid amplification of cDNA ends methods in grass carp Ctenopharyngodon idellus. Homology analysis showed that the CCK cDNA sequence of grass carp had the highest similarity (90 %) to that of goldfish Carassius auratus and a higher similarity (>70 %) to those of other teleosts than to mammals. The PCR amplification using genomic DNA identified that the CCK gene of grass carp was comprised of three exons and two introns. Real-time quantitative PCR was used to detect CCK mRNA expression in adult tissues. High levels of gene expression were found in the hypothalamus and pituitary; moderate levels in the intestine, muscle and white adipose tissue; and low levels in other tissues. During early development (i.e., fertilized eggs to 35-day post-hatching larvae) the levels of CCK mRNA expression were higher during embryonic developmental stages than during post-hatch larval stages. Fasting decreased CCK mRNA expression levels in the brain and intestine, whereas refeeding resulted in an increase of expression. The results suggest that CCK mRNA expression has obvious tissue specificity and may have a role in feed intake regulation in grass carp.     

Protein‐sparing capability of dietary lipid in herbivorous and omnivorous freshwater finfish: a comparative case study on grass carp (Ctenopharyngodon idella) and tilapia (Oreochromis niloticus × O. aureus)

Two, 8‐week feeding trials were conducted to compare protein‐sparing capability of dietary lipid in herbivorous grass carp (Ctenopharyngodon idella) and omnivorous tilapia (Oreochomis niloticus × O. aureus). Utilizing a 2 × 3 factorial design, experimental diets containing two levels of crude protein (380 and 250 g kg⁻¹) and three levels of lipid (0, 40 and 100 g kg⁻¹) were formulated for use in both feeding trials. Growth performances showed better response of both fish fed 380 g kg⁻¹ protein diet than those fed 250 g kg⁻¹ protein diet. Despite the dietary protein level, weight gain (WG), specific growth ratio (SGR), feed conversion ratio (FCR) and protein efficiency ratio were much higher (P < 0.05) for grass carp fed 40 g kg⁻¹ lipid diet than those fed 100 g kg⁻¹ lipid diet; however, there were no significant differences in tilapia fed the two diets. The feed intake of grass carp fed lipid‐free diet was the lowest, but it tended to decrease with increase in dietary lipids in tilapia. Lipid retention (LR) was negatively correlated with dietary lipid concentration of both fish. Viscerosomatic index (VSI), hepatosomatic index (HSI), intraperitoneal fat ratio (IPF) and whole‐body and liver lipid content positively correlated with dietary lipid concentration of both fish. Plasma parameters and liver enzymes activities were also positively correlated with dietary lipid concentration of both fish. Liver lipid contents were higher and enzymes activities were lower in grass carp when compared with tilapia. These data suggested that there was no evidence of a protein‐sparing effect of dietary lipids in grass carp. Tilapia has relatively higher capacity to endure high dietary lipid level compared to grass carp.     

Effect of Bacillus subtilis on Aeromonas hydrophila infection resistance in juvenile freshwater prawn, Macrobrachium rosenbergii (de Man)

This experiment was carried out to investigate the potential probiotics properties of Bacillus subtilis in protecting of juvenile freshwater prawn, Macrobrachium rosenbergii against Aeromonas hydrophila infection. A B. subtilis bacterium isolated from gut of juvenile prawns was added to the prawns feed at 10⁸ cells g^?1 feed. There were significant differences (P < 0.05) between B. subtilis-treated and control groups in growth and survival enhancement of juvenile prawns after 60 days of feeding trial. Sixty days after B. subtilis feeding trial, the prawns were challenged by bath exposure to A. hydrophila (10⁷ cells mL^?1) for 28 days. Four weeks after challenge, there was significant difference in the survival of prawns between B. subtilis-treated groups (88.33 %) and control groups (20.81 %; P < 0.05). In addition, the control groups had an unhealthy external appearance, while the treated groups, appeared healthy and normal. From this, it was concluded that the selected B. subtilis may be a promising probiotics for protection of prawns from A. hydrophila infection.     

Fat deposition pattern and mechanism in response to dietary lipid levels in grass carp, <Emphasis Type="Italic">Ctenopharyngodon idellus</Emphasis>

This study aimed to evaluate the fat deposition pattern and lipid metabolic strategies of grass carp in response to dietary lipid levels. Five isonitrogenous diets (260 g kg^?1 crude protein) containing five dietary lipid levels (0, 20, 40, 60, 80 g kg^?1) were fed to quadruplicate groups of 15 fish with initial weight 200 g, for 8 weeks. The best growth performance and feed utilization was observed in fish fed with lipid level at 40 g kg^?1. MFI and adipose tissue lipid content increased with increasing dietary lipid level up to 40 g kg^?1, and higher lipid level in diet made no sense. Fish adapted to high lipid intake through integrated regulating mechanisms in several related tissues to maintain lipid homeostasis. In the present study, grass carp firstly increased PPARγ and CPT1 expressions in adipose tissue to elevate adipocyte differentiation and lipolysis to adapt to high lipid intake above 40 g kg^?1. In liver, fish elevated hepatic lipid uptake but depressed biosynthesis of hepatic FAs, resulted in no difference in HSI and liver lipid content among the groups. Only in muscle, fish showed a significant fat deposition when the lipid intake above 40 g kg^?1. The excess lipid, derived from enhanced serum TC and TG contents, was more likely to induce deposition in muscle rather than lipid uptake by adipose tissue in grass carp fed with high dietary lipid, indicating the muscle of grass carp might be the main responding organ to high lipid intake.     

Hemato-immunological responses of Heros severus fed diets supplemented with different levels of Dunaliella salina

In this study, the effects of oral administration of different levels of Dunaliella salina (a natural β-carotene source) on growth parameters, immunological and hematological indices, as well as skin carotenoids, of Heros severus were investigated. One hundred and eighty H. severus weighing 27 ± 0.5 g were divided randomly into four groups in triplicate (15 fish in each replicate). Groups 1–4 received food supplemented with 0, 50, 100 and 200 mg kg^?1 D. salina powder, respectively. After 6 weeks, the growth parameters were compared among the groups. Blood samples were taken from each group, and hematological parameters including red blood cell count (RBC), white blood cell count (WBC), hematocrit (PCV), hemoglobin (Hb) and immunological indices (serum and mucus lysozyme and bactericidal activity, resistance against Aeromonas hydrophila infection) as well as carotenoid content of skin were evaluated. Results showed that some growth indices increased significantly in fish fed with 100 and 200 mg kg^?1 D. salina-supplemented food (P < 0.05). Although serum lysozyme activity was increased in fish fed with food supplemented with 100 and 200 mg kg^?1 D. salina (P < 0.05), no significant change was observed in serum and mucus bactericidal activity and mucus lysozyme activity among the groups (P > 0.05). Most of the hematological parameters such as WBC, RBC, PCV and Hb significantly increased in D. salina-treated fish compared with controls (P < 0.05). Mortality induced after challenge with A. hydrophila in 200 mg kg^?1 D. salina-treated fish was 36.67 %, which significantly decreased compared with control (P < 0.05). Skin carotenoid content in all D. salina treatments was statistically higher than that of control (P < 0.05). Conclusively, D. salina as a food additive can affect positively the growth, immunological and hematological parameters of H. severus.     

Investigation on protective effect of recombinant protein (OmpTS) of Aeromonas hydrophila in Common carp (Cyprinus carpio)

The outer membrane protein of Aeromonas hydrophila is a potential candidate for vaccine development. In this study, after cloning and expression of ompTS, 270 common carp, weighing 44 ± 5.7 g divided into five groups, were injected intraperitoneally twice with 3‐week intervals. Groups included the following: PBS, PBS plus Freund's adjuvant, recombinant protein, recombinant protein plus Freund's adjuvant and 20 fish as negative control. Two weeks after the second injection, 30 fish of each group were challenged with a dose of 2 × LD₅₀ of Aeromonas hydrophila and RPS was measured. The antibody level was measured using ELISA test. The protection of recombinant protein in the immunized fish with and without adjuvant, respectively, was about 82.61% and 78.26% (the protection of recombinant protein electroeluted from an SDS–PAGE with and without adjuvant, respectively, was about 78.62% and 69.57%). The average of antibody level in recombinant protein with and without adjuvant was significantly higher than the PBS group (p < .05). The ability of recombinant ompTS to increase the antibody level and to protect the fish from challenge by A. hydrophila demonstrated that recombinant ompTS protein injection can be used to immunize common carp against A. hydrophila infection.     

Establishment and characterization of a heart-derived cell line from goldfish (<Emphasis Type="Italic">Carassius auratus</Emphasis>)

The goldfish Carassius auratus, a freshwater fish in the family Cyprinidae, was one of the earliest fish to be domesticated for ornamental purposes. A cell line was established from goldfish heart (GH) tissue to create a biological monitoring tool for viral diseases. The GH cell line was optimally maintained at 25 °C in M199 medium supplemented with 10–20% fetal bovine serum. A chromosomal analysis indicated that the cell line remained diploid, with a mean chromosomal count of 100. In viral inoculation assays, significant cytopathic effects (CPEs) were caused by epizootic hematopoietic necrosis virus (EHNV), Andrias davidianus iridovirus (ADIV), and Bohle iridovirus (BIV) infections in the fish cells and the viral titers (average value) of EHNV, ADIV, and BIV in GH cells reached 10^5.0, 10^4.5, and 10^5.0 TCID₅₀/0.1 mL, respectively, within 7 days. However, no CPE was observed in the cells infected with viral hemorrhagic septicemia virus (VHSV), infectious hematopoietic necrosis virus (IHNV), spring viremia of carp virus (SVCV), infectious pancreatic necrosis virus (IPNV), channel catfish virus (CCV), or grass carp reovirus (GCRV). These results suggest that the GH cell line is a valuable tool for studying viral pathogenesis.     

Carbohydrate utilization by herbivorous and omnivorous freshwater fish species: a comparative study on gibel carp (Carassius auratus gibelio. var CAS III) and grass carp (Ctenopharyngodon idellus)

Two 8‐week feeding trials were conducted to evaluate dietary carbohydrate utilization by omnivorous gibel carp (Carassius auratus gibelio) (2.4 ± 0.1 g) and herbivorous grass carp (Ctenopharyngodon idellus) (6.5 ± 0.1 g). Five isonitrogenous (370 g kg^?1) and isolipid (70 g kg^?1) diets were formulated with increasing corn starch levels (60, 140, 220, 300 and 380 g kg^?1). Results showed that specific growth rate (SGR), feed efficiency (FE) and protein retention efficiency (PRE) of gibel carp significantly increased from dietary starch of 60 to 300 g kg^?1 and then decreased from 300 to 380 g kg^?1, but those of grass carp showed no significant differences between treatments. Independent of dietary starch levels, grass carp gained significantly higher FE and PRE than gibel carp. Feeding rate (FR) of gibel carp was significantly higher than that of grass carp. In two fish species, high dietary starch (300 and 380 g kg^?1) tended to obtain higher hepatosomatic index (HSI), serum triglyceride, hepatic lipid and body lipid contents. Serum glucose concentration of grass carp was not affected, while that of gibel carp fed the starch of 300 g kg^?1 diet was significantly lower than those of the fish fed other four diets (60, 140, 220 and 380 g kg^?1). Grass carp showed high tolerance to dietary starch while dietary corn starch should be no more than 300 g kg^?1 for gibel carp. High starch contents may cause lipid accumulation in the liver and body.     

Immunotoxic responses of chronic exposure to cypermethrin in common carp

In the current study, laboratory evaluations were made to assess the immunomodulatory effect of cypermethrin on fingerlings of common carp (Cyprinus carpio L.). Results showed that 96-h LC50 of cypermethrin in common carp was estimated at 0.85 μg/L. Fish were exposed for 21 days to cypermethrin at three sub-lethal concentrations of 0.042, 0.085, and 0.17 μg/L that represented 5, 10, and 20%, respectively, of the 96-h LC50 of the pesticide for this fish species. Blood samples were taken after 7, 14, and 21 days of exposure. Immunological indices and resistance against bacterial infection were determined. Compared to the control group, the fish exposed to cypermethrin showed a significant increase in neutrophil ratio but exhibited a significant decrease in leukocyte number and lymphocyte ratio in treatments exposed to 0.17 and/or 0.085 μg/L after 21 days of exposure (p < 0.05). Serum protein level was significantly decreased in group exposed to 0.17 μg/L on day 14 and also in groups exposed to 0.085 and 0.17 μg/L on day 21 (p < 0.05). Immunoglobulin value was significantly reduced in groups exposed to 0.085 and 0.17 μg/L after 21 days of exposure (p < 0.05). Serum lysozyme activity and phagocytic activity were significantly decreased following exposure to 0.17 μg/L determined on days 14 and 21, post-exposure (p < 0.05). Mortality rate following the challenge with Aeromonas hydrophila significantly increased in fish exposed to 0.17 μg/L of cypermethrin. Overall, the present results indicate severe immunotoxicological effects of cypermethrin in common carp. Therefore, the use of cypermethrin in the proximities of common carp farms should be carefully considered.     

Enhancement of protective immunity in blue gourami,Trichogaster trichopterus (Pallas), against Aeromonas hydrophila and Vibrioanguillarum by A. hydrophila major adhesin

Blue gourami, Trichogaster trichopterus (Pallas), were intraperitoneally immunized with major adhesin, a 43 kDa OMP protein isolated from fish Aeromonas hydrophila, in the presence of Freund's complete adjuvant (FCA). Three weeks later, a booster injection of adhesin without FCA was administered. Control group fish were similarly treated with phosphate‐buffered saline (PBS) and FCA. Results showed that anti‐adhesin serum obtained from fish after booster immunization exhibited very strong ability in agglutinating bacterial cells. Although this antiserum had no bactericidal effect, it could significantly inhibit serologically different strains of A. hydrophila from invading EPC (Epithelioma papillosum of carp) cells in vitro. In addition, the proliferative response of head kidney leucocytes of these immune fish was significantly increased as compared to that of the control. The results also showed that the major adhesin could provide significant protective immunity to fish against the challenge by homologous and heterologous strains of A. hydrophila and one virulent strain of Vibrio anguillarum.     

Environmental quality and natural food performance at feeding sites in a carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis>) pond

Just like other domesticated animals, common carp (Cyprinus carpio) are able to learn where food can easily be obtained. As a result, carp in semi-intensive polyculture ponds could conceivably restrict their main activity centres to supplemental feeding sites, leading to lowered exploitation of natural food resources (zooplankton and macrozoobenthos) and localised degradation of environmental conditions. At two semi-intensive ponds in southern Moravia (Czech Republic), areas around feeding sites displayed significantly reduced oxygen concentration and saturation (mainly p < 0.001). Likewise, temperature, pH and transparency also decreased significantly at feeding sites (mainly p < 0.05), while turbidity increased. While there was no significant difference in zooplankton biovolume at feeding and non-feeding sites, zoobenthos density and biomass were significantly lower at feeding sites (mainly p < 0.01). The feeding behaviour of carp, therefore, led to significant changes in both abiotic and biotic conditions at supplemental feeding sites.     

Effects of dietary pyridoxine on disease resistance,immune responses and intestinal microflora in juvenile Jian carp (Cyprinus carpio var. Jian)

This experiment was conducted to evaluate the effects of dietary pyridoxine on disease resistance, immune responses and intestinal microflora of fish. A total of 1050 Jian carp (11.71 ± 0.05 g) were randomly distributed into seven groups, feeding diets containing graded levels of pyridoxine (0.2, 1.7, 3.2, 5.0, 6.3, 8.6 and 12.4 mg kg^?1 diet). After 80 days of feeding, a challenge trial was conducted by injection of Aeromonas hydrophila for 17 days. Results indicated that with increasing dietary pyridoxine concentration up to 5.0 mg kg^?1 diet, survival rate after challenge with A.hydrophila and phagocytic activity of leukocyte were improved (P < 0.05), and plateaued thereafter (P > 0.05). Red blood cell and white blood cell counts were lowest when fed the diet containing 1.7 mg pyridoxine kg^?1 diet. Haemagglutination titre, lysozyme activity, acid phosphatase activity, total iron‐binding capacity, antibody titre and immunoglobulin M content followed the similar pattern to that observed with survival rate. Aeromonas hydrophila, Escherichia coli and Lactobacillus counts in intestine were not affected by dietary pyridoxine concentration (P > 0.05). These results suggested that pyridoxine could enhance immune response of fish.