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1.
Tilapias (Oreochromis niloticus) juveniles (total length 4.9 ± 0.2 cm and weight 1.8 ± 0.2 g) were exposed to several nitrite concentrations (0, 10, 18, 32, 56 and 100 mg l−1) for 96 h, using a semi-static renewal method at chloride levels of 35.0 and 70.0 mg l−1. At the end of the 96-h period, the median lethal concentration (LC50) of nitrite was 28.18 mg l−1 in water with low chloride content (35.0 mg l−1) and 44.67 mg l−1 with high chloride content (70.0 mg l−1, respectively). It indicated that high concentrations of chloride ions could reduce the toxicity of nitrite. During the toxicity experiments, the behaviour and clinical signs of tilapias were also observed. Furthermore, the test of toxic mechanism was designed taking five test concentrations, viz., 5, 10, 15 and 20 mg l−1 and a nitrite-free control. Nitrite exposure produced high levels of methaemoglobin (MHb) but did not seem to cause mortality, as surviving tilapias showed high levels (85.37 ± 2.23 and 53.82 ± 3.44 at 35.0 and 70.0 mg l−1 chloride, respectively). The percentage of MHb exposed to nitrite was significantly higher (P<0.05) than the control (0 mg l−1 nitrite) and increased with the increasing nitrite concentration. However, the percentage of MHb decreased with the increasing chloride concentration.  相似文献   

2.
Juvenile channel catfish (Ictalurus punctatus) were fed with nutritionally complete, basal diets supplemented with NaCl at 0, 10, 20 or 40 g kg?1 diet (0, 1, 2, or 4%) to apparent satiation twice daily for 10 weeks. Catfish were exposed to nitrite after six (7.70 mg L?1 nitrite‐N) and ten (7.18 mg L?1 nitrite‐N) weeks of feeding to determine the effect of dietary NaCl supplementation on resistance to nitrite toxicity. Fish were sampled before (baseline, pre‐exposure) and after 24‐h nitrite exposure to determine the effects of dietary NaCl on haematology (haematocrit, haemoglobin and methaemoglobin) and plasma electrolyte dynamics (nitrite, chloride, sodium and potassium). Mortality from nitrite toxicity was also determined. Mortality from nitrite exposure tended to decrease with increasing NaCl in the diet at 6 weeks and was significantly lower in the 40 g kg?1 NaCl group (12.5%) compared to the control group (57.5%). A similar trend in mortality occurred at 10 weeks as well; however, the differences among dietary treatments were not significant. The improvements in blood MetHb (non‐significant), chloride and nitrite levels in catfish may at least in part be responsible for the improved survival after nitrite exposure, which trended in support of the prevailing hypotheses for the positive effects of NaCl on nitrite toxicity.  相似文献   

3.
Abstract. Duplicate static bioassays were conducted for 168 h each to determine the median lelhal concentration (LC50) of nitrite (NO?2) for common carp, Cyprinus carpio L., fry at five different chloride (Cl?) levels. The acute toxicity of nilrite ceased towards the end of 96 h at all levels of chloride concentration. There was a highly significant positive correlation between the chloride concentration tested and the 96-h LC50. The 96-h LC50 values are 2·55, 5·77, 14·41 27·26 and 48·70 mgl?1 NO?2-N at chloride concentration of 1·0. 5·0, 10·5, 27·3 and 45·0 mgl?1 Cl? respectively. The linear relationship between chloride concentration and 96-h LC50 is best described by the equation: y= 1·03x+ 1·49 (r=+ 0·996; d.f. = 3;P <0·001), where y= 96 h LC50 of NO?2-N and x= concentration of Cl?. A NO?2-N to Cl? ratio of about 1:1·5–3·0 prevented complete mortality over the 168-h experimental period. A NO?2-N to Cl? ratio of 1:5 is recommended for protection of carp fry against nilrite mortality in fish farms.  相似文献   

4.
The effects of ammonia and nitrite on survival, growth and moulting were investigated in juvenile tiger crab, Orithyia sinica (carapace length 3.91±0.15 mm, carapace width 3.84±0.23 mm, n=440), after 30 days exposure to ammonia‐N (0, 20, 50, 100 and 150 mg L?1) and nitrite‐N (0, 50, 100, 150, 200 and 250 mg L?1) using a continuous flow system. Survival rates of tiger crab exposed to ammonia and nitrite decreased linearly with the exposure time and concentration. The growth rate of tiger crab exposed to 50, 100 and 150 mg L?1 ammonia was significantly lower than that of control crabs. The growth rate of tiger crab exposed to nitrite decreased at 150, 200 and 250 mg L?1 nitrite. During the ammonia and nitrite exposure, the intermoult period of the juveniles of tiger crab O. sinica was shortened between the first and second moult, and the number of moulting of crabs exposed to a higher concentration were significantly higher than that of control crabs.  相似文献   

5.
Effects of eugenol (AQUI‐S®20E, 10% active eugenol) sedation on cool water, yellow perch Perca flavescens (Mitchill), and warm water, Nile tilapia Oreochromis niloticus L. fish metabolic rates were assessed. Both species were exposed to 0, 10, 20 and 30 mg L?1 eugenol using static respirometry. In 17°C water and loading densities of 60, 120 and 240 g L?1, yellow perch controls (0 mg L?1 eugenol) had metabolic rates of 329.6–400.0 mg O2 kg?1 h?1, while yellow perch exposed to 20 and 30 mg L?1 eugenol had significantly reduced metabolic rates of 258.4–325.6 and 189.1–271.0 mg O2 kg?1 h?1 respectively. Nile tilapia exposed to 30 mg L?1 eugenol had a significantly reduced metabolic rate (424.5 ± 42.3 mg O2 kg?1 h?1) relative to the 0 mg L?1 eugenol control (546.6 ± 53.5 mg O2 kg?1 h?1) at a loading density of 120 g L?1 in 22°C water. No significant differences in metabolic rates for Nile tilapia were found at 240 or 360 g L?1 loading densities when exposed to eugenol. Results suggest that eugenol sedation may benefit yellow perch welfare at high densities (e.g. live transport) due to a reduction in metabolic rates, while further research is needed to assess the benefits of eugenol sedation on Nile tilapia at high loading densities.  相似文献   

6.
We evaluated the effects of chloride concentration on the clinical pathology in juvenile Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus (Mitchill), following semi‐static exposures to 1 mg L?1 nitrite for 96 h. In spring water naturally low in chloride (5 mg L?1), plasma nitrite concentrated to more than 40× environmental levels resulting in a severe methaemoglobinemia characterized by torpid behaviour, 30‐fold increase in methaemoglobin fraction, anaemia, leucopenia and hyperkalaemia. Loss of intracellular water and potassium to extracellular space may have resulted in hyperkalaemia and haemodilution. Fish survived nitrite exposure, but 60% of torpid fish died following capture and tissue sampling. Fish acclimated to 10‐fold higher chloride content (55 mg L?1) did not concentrate nitrite in the plasma above environmental levels or develop methaemoglobinemia, but did exhibit similar haematology and plasma chemistry changes. Plasma nitrite returned to preexposure levels by 14 days following nitrite exposures, but severity of clinical pathology changes persisted or increased, suggesting that Atlantic sturgeon have reduced capacity to recover from methaemoglobinemia. Fish that survive methaemoglobinemia may be susceptible to mortality from the cumulative effects of intoxication, handling and other stresses for two or more weeks following nitrite remediation. Chloride buffering in aquaculture systems reduces the toxic effects of nitrite accumulation.  相似文献   

7.
In the present study, the hypothesis tested was that Penaeus monodon post‐larvae (PL) experience lower growth when exposed to crushed conspecifics, which was achieved by exposing individual P. monodon PL with abundant food for 4 weeks to a gradient from 0 to 100 crushed conspecific PL L?1. Both dry weight (48.5±7.2 mg) and body size (28.0±1.3 mm) of animals exposed to 1 macerated PL L?1 were significantly (P≤0.011) higher than those of animals in treatments with 0, 5 and 10 crushed PL L?1 (average over treatments: 25.6±3.2 mg; 23.4±0.5 mm). All animals died within 1 week when exposed to 70 and 100 crushed PL L?1, and within 3–4 weeks when exposed to 50 and 30 crushed PL L?1. Exposure time affected mortality and it appeared that LC50 values decreased from 60 to 13 crushed PL L?1 from 1 to 4 weeks' exposure. Survival of P. monodon PL was negatively correlated to pH, biological oxygen demand, ammonia and nitrate. In conclusion, low dose of crushed conspecifics has a stimulatory effect on P. monodon PL, as larvae were heavier and larger, while high doses cause high mortality.  相似文献   

8.
A study was conducted to optimize stocking density of freshwater prawn, Macrobrachium rosenbergii, in carp polyculture for 3 months in 10 experimental ponds of 80 m2. Five stocking densities of prawn, 2500, 5000, 7500, 10 000 and 12 500 ha?1, were assigned to treatments T1, T2, T3, T4 and T5 respectively. The densities of catla, Catla catla, rohu, Labeo rohita and silver carp, Hypophthalmicthys molitrix, were 2500, 5000, and 2500 ha?1, respectively, in each treatment. Each treatment had two replicate ponds. The mean initial weights of prawn, catla, rohu and silver carp were 1.1±0.02, 8.28±0.1, 25.2±1.1 and 36.32±1.2 g respectively. A pelleted diet containing 30% protein was prepared using fish meal, meat and bone meal, mustard oilcake, rice bran, wheat bran and molasses, and was fed twice daily at a rate of 5% of fish biomass. Water quality parameters were measured fortnightly and the ranges of temperature, pH and dissolved oxygen were 27.5–1.3°C, 6.9–8.6 and 4.5–8.6 mg L?1 respectively. Feed conversion ratios ranged from 2.05 to 2.20 among the treatments. Per cent survival (%) of prawns ranged from 72% to 78%, while it varied from 80% to 93%, 90% to 95% and 90% to 92% for catla, rohu and silver carp respectively. The results showed that there were no significant differences among the weight gains of prawn and carp in different treatments. However, the overall total production of prawn and fish together was significantly (P<0.05) higher in T3 and T4 compared with other treatments. The total production for 3 months ranged between 2618 and 2916 kg ha?1. The production of prawn was significantly higher (361.3 kg ha?1) in T5 with a highest stocking density of 12 500 prawn ha?1. Although there was no significant difference (P>0.05) between the total production of prawn and fish together in T3 and T4, the highest net profit (Tk. 69 006 ha?1) was obtained in T4. Therefore, from the result of the study it may be concluded that a stocking ratio of 4:1:2:1 of prawn:catla:rohu:silver carp at a total density of 20 000 ha?1 may be recommended for prawn–carp polyculture in ponds.  相似文献   

9.
This study was performed to estimate the nitrite toxicity to southern flounder, Paralichthys lethostigma, in brackish water (7.5 ppt of salinity). For a LC50 test, 20 fingerlings (5.7 ± 0.4 cm) in each aquarium (15 L) were exposed to the concentrations of 0, 1, 5, 10, 15, 30, 60, 120, and 240 mg NO2?‐N/L in duplication for 10 d. Median lethal concentration at 96 h (96‐h LC50) was calculated as 81.6 mg NO2?‐N/L. For a verification test, young flounder (164.2 ± 9.1 g) were exposed to a simulated culture condition in recirculating systems (1000 L). Sodium nitrite was not added to control system, whereas it was added to Treatment system 1 (TS 1) and Treatment system 2 (TS 2) to maintain nitrite concentrations of 20 and 30 mg NO2?‐N/L, respectively. The plasma nitrite concentrations of the young flounder in TS 1 and TS 2 were 4.5 and 6.6 mg NO2?‐N/L, respectively, after 2 wk. At this time, the methemoglobin percentages in TS 1 and TS 2 reached 85.8 and 89.7%, and survival rates were 37.5 and 25.0%, respectively. The results of these tests indicate that southern flounder do not concentrate nitrite in blood from the environment, but they seem to be more sensitive to nitrite compared with other species that do not concentrate nitrite.  相似文献   

10.
Exposure to TEX‐OE®, a patented extract of the prickly pear cactus (Opuntia ficus indica) containing chaperone‐stimulating factor, was shown to protect common carp, Cyprinus carpio L., fingerlings against acute ammonia stress. Survival was enhanced twofold from 50% to 95% after exposure to 5.92 mg L?1 NH3, a level determined in the ammonia challenge bioassay as the 1‐h LD50 concentration for this species. Survival of TEX‐OE®‐pre‐exposed fish was enhanced by 20% over non‐exposed controls during lethal ammonia challenge (14.21 mg L?1 NH3). Increase in the levels of gill and muscle Hsp70 was evident in TEX‐OE®‐pre‐exposed fish but not in the unexposed controls, indicating that application of TEX‐OE® accelerated carp endogenous Hsp70 synthesis during ammonia perturbation. Protection against ammonia was correlated with Hsp70 accretion.  相似文献   

11.
Four experiments were conducted to evaluate the effects of calcium and magnesium hardness on the acute toxicity of copper sulphate to Indian major carp, rohu (Labeo rohita, Hamilton) fingerlings and juvenile catfish (Channa punctatus, Bloch) in medium alkalinity experiments. A preliminary bioassay determined the 96 h LC50 of copper sulphate to be 0.56 mg L?1 for L. rohita fingerlings and 11.78 mg L?1 for juvenile C. punctatus placed in water with calcium hardness and total alkalinity set at 100 mg L?1 CaCO3. In the first experiment, rohu were exposed to 0.56 mg L?1 copper sulphate in environments where calcium hardness was varied from 50 to 350 mg L?1 CaCO3 and total alkalinity was 100 mg L?1 CaCO3. As calcium hardness increased, copper‐induced rohu mortalities decreased significantly from 90% at 50 mg L?1 CaCO3 to 7% at 350 mg L?1 CaCO3. In the second experiment, rohu were exposed to 0.56 mg L?1 copper sulphate in environments where magnesium hardness was varied from 50 to 350 mg L?1 CaCO3 with total alkalinity set at 100 mg L?1 CaCO3. Hundred percent mortality was observed in magnesium‐based hardness treatments. In the third experiment, catfish were exposed to 11.78 mg L?1 copper sulphate in environments where calcium hardness was varied from 50 to 400 mg L?1 and total alkalinity was 100 mg L?1 CaCO3. As calcium hardness increased, copper‐induced catfish mortalities decreased significantly from 90% at 50 mg L?1 CaCO3 to 4% at 400 mg L?1 CaCO3. In the fourth experiment, catfish were exposed to 11.78 mg L?1 copper sulphate in environments where magnesium hardness was varied from 50 to 400 mg L?1 CaCO3, with total alkalinity set at 100 mg L?1 CaCO3. In this case, 100% mortality was also observed in magnesium‐based treatments. Mortality rates in magnesium hardness treatments were consistent with those in the second experiment. These data suggest a calcium‐specific mechanism with respect to acute copper toxicity both in rohu and catfish.  相似文献   

12.
This study aimed to evaluate the tolerance of common snook Centropomus undecimalis larvae and juveniles exposed to acute concentrations of un-ionized ammonia for 96 h at 35g L?1 salinity, after 24 h starvation. For that, 10 larvae (20.85 ± 1.46 mm) of 47 days post hatch (DPH) per experimental unit (1.5 L) were exposed to 0.00 ± 0.00, 0.65 ± 0.04, 1.29 ± 0.09, 2.59 ± 0.18, 3.88 ± 0.27, 5.17 ± 0.34, and 6.47 ± 0.43 mg L?1 NH3, in triplicates, at 26.72 ± 0.08°C, dissolved oxygen at 5.72 ± 0.10 mg L?1 and pH 8.45 ± 0.06. During this period, no mortalities were observed. Another trial was performed with five juveniles (20.35 ± 6.10 g, 13.90 ± 1.75 cm) per experimental unit (60 L) exposed to 0.00 ± 0.00, 2.26 ± 0.07, 2.68 ± 0.11, 3.20 ± 0.13, 3.68 ± 0.17, and 4.27 ± 0.16 mg L?1 NH3, in triplicates, at 21.90 ± 0.76°C, dissolved oxygen at 6.27 ± 0.21 mg L?1 and pH at 8.38 ± 0.04. Fish mortality increased as ammonia concentrations increased at each day, and LC50 96 h was 3.52 mg L?1 NH3. Larvae were less sensitive than juveniles, demonstrating that the environmental toxicity of ammonia to common snook is influenced by age. Sublethal exposition to ammonia caused histological damages in gills of common snook juveniles and variation on glucose levels, hematocrit, and red blood cells number, showing negative effects on fish homeostasis. Moreover, compared to other species, the common snook has great resistance to ammonia.  相似文献   

13.
Nitrite is usually found in aquatic environments where nitrification process occurs. This ion can cause several injuries to aquatic species, particularly fish. Nitrite reacts with haemoglobin yielding the non‐functional methaemoglobin, which leads to many physiological consequences such as functional anaemia and supposed hypoxia. Metabolism of the freshwater teleost matrinxã, Brycon amazonicus, exposed to environmental 0.6 mg L?1 of nitrite N‐NO2? for 96 h was studied, and the fermentative/oxidative preference was gauged. Concentrations of glycogen, glucose, lactate, pyruvate and ammonia, plus the activities of lactate, glutamate and malate dehydrogenase were assayed. The exposure resulted in a metabolic profile that allowed inferring the continuity of oxidative metabolism. Catabolism of amino acids prevailed or was apparently exacerbated by inferred branchial injury and consequent impairment of nitrogen excretion. Moreover, the studied enzymes glutamate dehydrogenase, lactate dehydrogenase and malate dehydrogenase from brain and heart were little affected by nitrite. The expected fermentative metabolism due to the high methaemoglobin formation was not observed.  相似文献   

14.
In this research, the mineral and organic composition of the seminal plasma, physical spermatological parameters and their physiological relationships were investigated in grass carp (Ctenopharyngodon idella). The seminal plasma contained 98.14±5.23 mM L?1 (Na+), 380.85±25.95 mM L?1 (K+), 30.25±4.96 mg dL?1 (Ca2+), 19.16±1.70 mEq L?1 (Mg2+), 1.36±0.11 mg dL?1 glucose, 0.37±0.08 g dL?1 total protein, 12.02±1.18 mg dL?1 cholesterol, 14.85±1.50 mg dL?1 triglyceride and 43.5±9.56 mg dL?1 urea. The following spermatological parameters were found: sperm volume 14.44±1.16 mL, sperm motility 80.60±1.55%, movement duration 67.68±4.32 s, density 15.43±0.72 × 109 mL?1, total density 337.43+45.86 × 109 and pH 7.24±0.17. The Na+ and Ca2+ ions correlated negatively with spermatozoa motility (r=?0.453, P>0.05 and r=?0.192, P>0.05) respectively. The K+ ion correlated positively with spermatozoa motility (r=0.545, P>0.05). But a statistically significant correlation was not observed between sperm motility and seminal plasma parameters. The following correlations were observed between mineral and organic components. The Mg2+ was positively correlated with glucose and cholesterol (r=0.692, P<0.05 and r=0.680, P<0.05) respectively. A highly significant positive relationship was also found between Mg2+ and total protein (r=0.837, P<0.01). On the other hand, a significantly negative relationship was found between Ca2+ and triglyceride (r=?0.639, P<0.05). These parameters should be considered when developing procedures for either artificial fertilization or for cryopreservation of grass carp sperm.  相似文献   

15.
In this study, we tested the lower salinity tolerance of juvenile shrimps (Litopenaeus vannamei) at a relatively low temperature (20 °C). In the first of two laboratory experiments, we first abruptly transferred shrimps (6.91 ± 0.05 g wet weight, mean ± SE) from the rearing salinity (35 000 mg L?1) to salinities of 5000, 15 000, 25 000, 35 000 (control) and 40 000 mg L?1 at 20 °C. The survival of L. vannamei juvenile was not affected by salinities from 15 000 to 40 000 mg L?1 during the 96‐h exposure periods. Shrimps exposed to 5000 mg L?1 were significantly affected by salinity, with a survival of 12.5% after 96 h. The 24‐, 48‐ and 96‐h lethal salinity for 50% (LS50) were 7020, 8510 and 9540 mg L?1 respectively. In the second experiment, shrimps (5.47 ± 0.09 g wet weight, mean ± SE) were acclimatized to the different salinity levels (5000, 15 000, 25 000, 35 000 and 40 000 mg L?1) and then maintained for 30 days at 20 °C. Results showed that the survival was significantly lower at 5000 mg L?1 than at other salinity levels, but the final wet weight under 5000 mg L?1 treatment was significantly higher than those under other treatments (P<0.05). Feed intake (FI) of shrimp under 5000 mg L?1 was significantly lower than those of shrimp under 150 00–40 000 mg L?1; food conversion efficiency (FCE), however, showed a contrasting change (P<0.05). Furthermore, salinity significantly influenced the oxygen consumption rates, ammonia‐N excretion rates and the O/N ratio of test shrimps (P<0.05). The results obtained in our work provide evidence that L. vannamei juveniles have limited capacity to tolerate salinities <10 000 mg L?1 at a relatively low temperature (20 °C). Results also show that L. vannamei juvenile can recover from the abrupt salinity change between 15 000 and 40 000 mg L?1 within 24 h.  相似文献   

16.
The present study examined the protective effects of water chloride (Cl?) towards nitrite toxicity in Atlantic salmon parr during 84‐day long nitrite exposure. Effects on growth, histology, blood indices and gene expression were studied at a fixed nominal Cl? concentration of 200 mg/L and at several water nitrite concentrations (0, 0.5, 2, 5 and 10 mg/L NO2?–N). The specific growth rate was significantly reduced during the first three weeks at a Cl:NO2?–N ratio of 21:1, suggesting the activation of coping mechanisms at the later stages of the experiment. No significant effect of nitrite on gill histology and mortality was found. Nitrite accumulated in plasma; however, a Cl:NO2?–N ratio of 104:1 or higher prevented nitrite entry. The concentration of NO2?–N in plasma was significantly reduced at the end of the study, supporting the hypothesis of coping mechanisms. Cystic fibrosis transmembrane conductance regulator (cftr)‐1 showed a significant up‐regulation at highest nitrite concentration on day 22, and in three of the highest exposure groups at the end of the experiment. Our findings suggest that a Cl:NO2?–N ratio above 104:1 should be maintained through episodes of nitrite accumulation in water during the production of Atlantic salmon parr.  相似文献   

17.

The aim of this study was to investigate the possibility of improving the growth and physiological indices of plant and fish by adding different levels of ascorbic acid (vitamin C) to water in the aquaponic system using Nile tilapia (Oreochromis niloticus) and saffron plant (Crocus sativus). 240# fish (12.5?±?0.21 gr) and 120# saffron corms (2.8?±?0.12 gr) were randomly assigned to 15 experimental units and underwent treatments of adding 0 (control), 2, 4, 6, and 8 mg L?1 ascorbic acid to water, every 6 days, for 8 weeks. The fish final weight and subsequently other growth performance indices increased in the treatment of 4 mg L?1 vitamin C compared to other treatments (P?≤?0.05). Some growth performances of saffron plants such as saffron production, in treatment of 6 mg L?1, were significantly higher than the control group and reached from 17.34?±?0.27 mg flower?1 in the control group to 25.4?±?1.61 mg flower?1 in treatment of 6 mg L?1. Measuring the serum biochemical parameters of the fish showed that, in the treatment of 8 mg/L ascorbic acid, the cortisol content in the blood reached its maximum (21.49?±?2.42 µg dL?1). The trypsin activity in proximal intestine and mid-intestine significantly increased in treatments of 2, 4, and 6 mg L?1, respectively. The current experiment showed that, by adding 4–6 mg/L ascorbic acid to the aquaponic system water (every 6 days), the optimal levels of Nile tilapia and saffron plant growth performances would occur.

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18.
A feeding experiment was conducted to investigate the effects of high dietary intake of vitamin E (supplied as dl ‐α‐tocopheryl acetate) and n‐3 highly unsaturated fatty acid (n‐3 HUFA) on the non‐specific immune response and disease resistance in Japanese flounder Paralichthys olivaceus. Nine practical diets were formulated to contain one of three levels of vitamin E namely, 0, 80 or 200 mg kg?1 (the total α‐tocopherol contents in the diets were 21, 97 and 213 mg kg?1 based on analysis), and at each vitamin E level with one of three n‐3 HUFA levels i.e. 0.5%, 1.5% or 2.0%. Each diet was randomly assigned to triplicate groups of Japanese flounder (initial body weight: 40.5±1.0 g, mean±SD) in a re‐circulation rearing system. Fish were fed twice daily to apparent satiation at 07:00 and 18:00 hours for 12 weeks. During the experimental period, water temperature was maintained at 18±1°C, salinity 31–35 g L?1, and pH 7.8–8.2. Dissolved oxygen was not less than 6 mg L?1, and there were negligible levels of free ammonia and nitrite. The results showed that the increase in dietary n‐3 HUFA from 0.5% to 1.0% significantly decreased muscle α‐tocopherol contents in fish‐fed diets with 21 and 97 mg α‐tocopherol kg?1 diet (P<0.05). In 1.0% HUFA groups, alternative complement pathway activity (ACH50) of fish fed the diet containing the 213 mg α‐tocopherol kg?1 diet was significantly higher than noted for fish fed the diet containing 97 mg α‐tocopherol kg?1 diet (P<0.05). Fish fed the diet with 213 mg α‐tocopherol kg?1 and 2.0% n‐3 HUFA had the highest lysozyme activity (131.7 U mL?1) among all the dietary treatments. Fish fed the diets containing 97 and 213 mg α‐tocopherol kg?1 with 1.0% n‐3 HUFA had significantly higher respiratory burst activity than those fed the diets containing 21 mg α‐tocopherol kg?1 with 0.5 and 1.0% n‐3 HUFA (P<0.05). In the disease resistance experiment, high intake of dietary vitamin E with 213 mg α‐tocopherol kg?1 significantly decreased cumulative mortality and delayed the days to first mortality after a 7‐day Edwardsiella tarda challenge (P<0.05). In addition, under the experimental conditions, dietary vitamin E and n‐3 HUFA had a synergistic effect on the non‐specific immune responses and disease resistance in Japanese flounder (P<0.05).  相似文献   

19.
Silver catfish, Rhamdia quelen (Quoy & Gaimard, 1824), is an endemic species from Latin America that is raised in cultivation ponds, and consequently may be exposed to low oxygen levels. Therefore, the objective of this study was to verify the lethal concentration (CL50?96 h) of dissolved oxygen levels for silver catfish juveniles. In addition, the effects of different dissolved oxygen levels (1.96±0.08, 3.10±0.10, 4.14±0.09, 5.20±0.07 and 6.16±0.03 mg L?1) on growth and metabolic parameters (glycogen, glucose, protein, lactate levels and catalase activity) were also investigated. CL50?96 h was 0.52 mg L?1 (CI 0.42–0.61 mg L?1) or 6.7% oxygen saturation. After exposure of silver catfish to hypoxia for 30 days, there were no changes in biochemical parameters indicating the use of an anaerobic pathway by the fish. However, the dissolved oxygen levels influenced silver catfish juvenile behaviour, survival and growth, and under the experimental conditions 5.2 mg L?1 (or 65.6% oxygen saturation) is the minimum oxygen level recommended for the growth of this species.  相似文献   

20.
Carp respond to water hypoxia with an evaluation in the rate of gill ventilation. In order to characterize closer the adequate stimulus for the increase in respiratory drive specimens of carp, Cyprinus carpio L., were exposed simultaneously to moderate environmental hypoxia (PwO2? 75mmHg, 10kPa) and elevated water nitrite concentration (089 ± 0-lmmol/l) for 24h. The differential effects of these treatments were utilized to distinguish between the responses to an immediate reduction in water and arterial Poa (P,O2), and to the slowly developing reduction of arterial oxygen content (CaO2) and functional oxygen saturation (SaO2). After onset of hypoxia gill ventilation quickly increased, leading to a reduction in PaCO2. Slowly rising blood methaemoglobin levels resulted in a gradual decline in CaO2 and SaO2 over 24h, whereas P002 remained steady for the entire exposure period. This pattern of lowered Paco2 and PaO2, essentially constant for 24 h, together with the lack of any correlation with changes in CaO2, suggests PO2 (Pa,O2 and/or Pwo2) as the primary stimulus in the regulation of ventilation of carp.  相似文献   

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