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1.
The aim of the present study was to assess survival rate, Zn accumulation, reactive oxygen species (ROS) levels, oxidative damage and antioxidant responses after Zn exposure (2 and 8 mg L?1 Zn) at different exposure times (6, 12, 24, 48 and 96 h) in the liver of large yellow croaker. Survival rate was reduced at 96 h, and hepatic Zn content increased during 24–96 by 8 mg L?1 Zn. In the 2 mg L?1 Zn group, no fish died and the increase in Zn content merely occurred at 96 h. Exposure to 8 mg L?1 Zn induced accumulation of ROS, lipid peroxidation and protein carbonylation during the late stage of exposure. In contrast, exposure to 2 mg L?1 Zn did not result in oxidative damage, which may result from the up-regulation of antioxidant defenses. Although exposure to 8 mg L?1 Zn increased activities and mRNA levels of antioxidant enzymes during the early stage of exposure, including Cu/Zn–SOD, Mn–SOD, CAT, GPx and GR, the activities of these enzymes except Cu/Zn–SOD were inhibited at 96 h. Furthermore, a sharp increase in Nrf2 expression was observed in fish exposed to 8 mg L?1 at 6 and 12 h, and 2 mg L?1 at 12 h and 24 h, suggesting that Nrf2 was required for the protracted induction of these genes. The late increase in Keap1 expression may support its role in switching off the Nrf2 response. In conclusion, the present study demonstrated different effects of low- and high-dose waterborne Zn on antioxidant responses, which could contribute to the understanding of antioxidant and toxic roles of zinc on a molecular level.  相似文献   

2.
This study investigated the secondary stress responses of Paralichthys orbignyanus exposed to ammonia and nitrite and after recovery. Fish were exposed to 0.12, 0.28, and 0.57 mg NH3‐N/L, or 5.72, 10.43, and 15.27 mg NO2‐N/L for 10 d followed by the same time length for recovery. Ammonia‐ and nitrite‐free water was used as a control treatment. Blood samples were collected after 1, 5, and 10 d of exposure and after recovery. Fish exposed to ammonia presented lower and higher glucose levels after 10 d of exposure and recovery, respectively. Ammonia induced initial and transient ionic disturbances and metabolic alkalosis. Nitrite exposure caused hyperglycemia, increased plasma K+ levels, and respiratory alkalosis, whereas metabolic acidosis was observed after recovery. Increased proportion of monocytes and/or granulocytes and reduced number of lymphocytes were demonstrated in fish exposed to 0.28 mg NH3‐N/L (Day 1) and 10.43 mg NO2‐N/L (Day 5) and after recovery in the 0.28 and 0.57 mg NH3‐N/L treatments. Exposure to ammonia decreased the proportion of granulocytes on Day 5. In conclusion, exposure to concentrations at 0.12 mg NH3‐N/L and 5.72 mg NO2‐N/L provoked physiological disorders in Brazilian flounder. Nonetheless, fish exposed to 5.72 mg NO2‐N/L following a 10‐d recovery period showed complete resumption of homeostasis.  相似文献   

3.
The present study aimed to assess the possible preventive and reparative effects of isoleucine (Ile) against copper (Cu)-induced oxidative stress in fish enterocytes in vitro. In experiment 1, enterocytes were preincubated with increasing concentrations of Ile (0, 50, 120, 190, 260, and 330 mg L?1) for 72 h followed by exposure to 6 mg L?1 Cu for 24 h. In experiment 2, the enterocytes were pretreated with 6 mg L?1 Cu for 24 h and then treated with 0–330 mg L?1 Ile for 72 h to investigate its potential reparative role. The results of experiment 1 showed that Cu exposure increased lactate dehydrogenase (LDH) activity and malondialdehyde and protein carbonyl (PC) content; these changes were completely suppressed by pretreatment with Ile at optimum concentrations (P < 0.05). Moreover, Ile pretreatment prevented the decrease in superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in the enterocytes exposed to Cu (P < 0.05). Additionally, cells exposed to Cu exhibited adaptive increases in glutathione-S-transferase (GST) activity. In experiment 2, the LDH activity and protein oxidation induced by Cu were completely reversed by Ile posttreatment. Meanwhile, the Cu-induced decrease in SOD, GPx, and GST activity was completely reversed by subsequent Ile treatment, but the reduced glutathione content was not restored. Collectively, these results indicate that Ile suppresses Cu-induced oxidative damage via preventive and reparative pathways in primary enterocytes and thus protects the structural integrity of enterocytes in fish.  相似文献   

4.
False clownfish, Amphiprion ocellaris, is one of the most commercialized fish species in the world, highly produced to supply the aquarium market. The high stocking densities used to maximize fish production can increase ammonia and nitrite to toxic levels. In this study, A. ocellaris juveniles (1.20 ± 0.34 g) were exposed to six concentrations of ammonia ranged from 0.23 to 1.63 mg/L NH3-N and eight concentrations of nitrite (26.3–202.2 mg/L NO2 ?-N). The LC50- 24, LC50-48, LC50-72 and LC50-96 h were estimated to be 1.06, 0.83, 0.75 and 0.75 mg/L for NH3-N and 188.3, 151.01, 124.1 and 108.8 mg/L for NO2 ?-N. Analysis of gill lesions caused by sublethal concentrations of these nitrogenous compounds showed that both nitrogenous compounds induced tissue lesions such as hyperplasia of epithelium cells, hypertrophy of chloride cells and lamellar lifting to all concentrations tested. However, histopathological alterations were more conspicuous accordingly the increase of ammonia or nitrite in fish exposed to 0.57 mg/L NH3-N or 100 mg/L NO2 ?-N. Based on our results, we recommend to avoid concentrations higher than 0.57 mg/L of NH3-N and 25 mg/L of NO2-N in water.  相似文献   

5.
This study determined effects of nitrate (NO3?)‐induced stress on faecal cortisol levels in koi (Cyprinus carpio). NO3? was presented in two formats: (1) bulk increase followed by dilution to assess cortisol response and recovery and (2) bulk increase followed by incremental increases to assess cortisol response limit. Fish were maintained group‐wise in treatment and control aquaria (n=6 per group), and 0.5 g L?1 NO3? (as NaNO3) was added to the water. Faecal samples were collected daily and blood samples were taken pretreatment and 72‐h posttreatment and were assayed for cortisol via ELISA. NO3? increased plasma and faecal cortisol 4.4‐fold and 3.9‐fold respectively. Plasma cortisol was not measured further. After a 74% NO3? decrease by dilution, faecal cortisol decreased to baseline within 24 h, and restimulation by NO3? (1.0 g L?1) elevated faecal cortisol to maximal study levels. In a separate experiment, exposure to 0.4 g L?1 NO3? increased faecal cortisol 6.9‐fold. However, three additional 0.4 g L?1 NO3? increments across 9 days did not further increase cortisol. This study demonstrates that faecal cortisol measurement in fish via an ELISA can be useful as an indicator of NO3?‐induced stress in the aquatic environment.  相似文献   

6.
Copper is an essential element, but at high concentrations, it is toxic for living organisms. The present study investigated the responses of goldfish, Carassius auratus, to 96 h exposure to 30, 300, or 700 μg L?1 of copper II chloride (Cu2+). The content of protein carbonyls was higher in kidney (by 158%) after exposure to 700 mg L?1 copper, whereas in gills, liver, and brain, we observed lower content of protein carbonyls after exposure to copper compared with control values. Exposure to copper resulted in increased levels of lipid peroxides in gills (76%) and liver (95–110%) after exposure to 300 and 700 μg L?1 Cu2+. Low molecular mass thiols were depleted by 23–40% in liver and by 29–67% in kidney in response to copper treatment and can be used as biomarkers toxicity of copper. The activities of primary antioxidant enzymes, superoxide dismutase and catalase, were increased in liver as a result of Cu2+ exposure, whereas in kidney catalase activity was decreased. The activities of glutathione-related enzymes, glutathione peroxidase, glutathione-S-transferase, and glutathione reductase were decreased as a result of copper exposure, but glutathione reductase activity increased by 25–40% in liver. Taken together, these data show that exposure of fish to Cu2+ ions results in the development of low/high intensity oxidative stress reflected in enhanced activities of antioxidant and associated enzymes in different goldfish tissues.  相似文献   

7.
Influence of nitrite on two fish species, Eurasian perch (Perca fluviatilis L.) and largemouth bass (Micropterus salmoides Lacépède), was assessed in two acute toxicity tests. In the first one, lethal concentrations (48hLC50) of nitrite were estimated at 11 mg l?1 NO2 ? for perch and 882 mg l?1 NO2 ? for bass. In the second test, fishes were exposed for 48 h to concentrations representing ¼ and ½ value of 48hLC50 for each species. This test showed that the higher nitrite concentration in the water the higher methaemoglobin content in the blood, and nitrite levels in the blood plasma were observed in both species. On the other hand, leucocyte count showed opposite trend. Activity of NADH-methaemoglobin reductase was markedly lower in largemouth bass compared to Eurasian perch and was stimulated by nitrite exposure in neither of the species.  相似文献   

8.
In the current study, we set up a denitrification process to remove the nitrogen pollutants, especially nitrate (NO3–-N), from the wastewater after a nitrification-based biofloc technology (BFT) aquaculture cycle. Five different treatments (CN0, CN1, CN2, CN4 and CN6, respectively) were used, which involved addition of extra carbohydrate with variable ratios of elementary organic carbon to NO3–-N by weight (C/NO3–-N ratio equal to 0, 1, 2, 4, and 6, respectively). With CN2, CN4, and CN6 treatments, NO3–-N was decreased (with increasing alkalinity) to ≤ 6.42 ± 0.30 mg·L−1 and low amounts (close to zero) of nitrite (NO2–-N) were achieved. However, there were high concentrations of residual NO3–-N and/or NO2–-N in CN0 and CN1. CN2 achieved the best denitrification, wherein 81.00 ± 0.95% of the initial input nitrogen was removed. By fitting the equations, the highest nitrogen recycling rate (23.08 mg-N·g-C−1) was achieved with a C/NO3–-N ratio of 4.16. Denitrifying bacteria were the dominant bacteria in all extra carbohydrate added treatment groups. Although denitrifying polyphosphate accumulating organisms contributed to the removal of phosphorus, high concentrations of residual soluble reactive phosphate (SRP) were observed in all treatment groups. Overall, extra addition of carbohydrate with C/NO3–-N ratio ≥ 2 is advisable for nitrogen removal, while the highest nitrogen recycling rate will be achieved with a ratio of 4.16.  相似文献   

9.
The objective of this study was to assess the effects of stocking density on growth performance, serum biochemical parameters, and muscle texture properties of genetically improved farmed tilapia (Oreochromis niloticus, GIFT). Juvenile GIFT with an average initial weight of 12.54?±?0.45 g (mean?±?SD) were randomly stocked in 16 tanks (80 L) in a recirculation aquaculture system at four densities of 10 (D1), 20 (D2), 30 (D3), and 40 (D4) fish per tank for 56 days, with quadruplicate for each density. There were no significant differences in water temperature among the four treatments (P?>?0.05). D4 had the significantly lowest dissolved oxygen content (5.52 vs 5.69–6.09 mg L?1) (P?>?0.05) and pH (6.63 vs 6.87–7.20) (P?<?0.05). NO2-N and NH4-N concentrations significantly increased with increasing stocking density (P?<?0.05). Weight gain (WG) and specific growth rates (SGR) decreased with increasing stocking density. The lowest WG (617.20 vs 660.45–747.06%), SGR (3.52 vs 3.62–3.81% day?1), and highest feed conversion ratio (1.68 vs 1.53–1.58) were observed in D4. Fish at D4 had significantly lower condition factor (3.11 vs 3.29–3.37%) and survival rate (91.25 vs 97.50%) than those from D1 and D2 (P?<?0.05). With increasing stocking density, serum total cholesterol, triglyceride, and total protein concentrations decreased (P <?0.05) and aspartate aminotransferase and alanine aminotransferase activities increased (P <?0.05). D4 fish had higher moisture content (78.80 vs 76.97%) and lower crude protein content (18.14 vs 19.39%) in muscle than D1 fish (P?<?0.05). Compared to D1 and D2, D3 and D4 had lower muscle hardness (1271.54–1294.07 vs 1465.12–1485.65 g), springiness (0.62–0.65 vs 0.70–0.72), gumminess (857.33–885.32 vs 1058.82–1079.28 g), and chewiness (533.04–577.09 vs 757.53–775.69 g) (P <?0.05). High stocking density resulted in growth inhibition, declines in flesh quality, and disturbance to several serum biochemical parameters.  相似文献   

10.
Bacterial diseases cause tilapia's high‐mortality outbreak. This study investigated the toxicity of azithromycin (AZT), a macrolide antibiotic that has been considered a possible therapeutic drug for tilapia aquacultural use. The 48‐h acute toxicity (50% lethal concentration, LC50; 48 h) of AZT was determined for Oreochromis niloticus. Thereafter, fish were exposed to 0, 1, 50 and 100 mg L?1 AZT during 14 days (chronic exposure) and measured the haematological variables, the activity of superoxide dismutase, catalase, glutathione peroxidase, glutathione‐S‐transferase (GST) and the concentration of glutathione (GSH), protein carbonyl and lipid peroxidation in the liver; histopathology was analysed the liver, gills and kidneys. The LC50; 48 h was >100 mg L?1. No fish died during chronic exposure. Haematocrit and haemoglobin concentration increased in fish exposed to 50 and 100 mg L?1, and the total number of leucocyte and thrombocyte increased after exposure to 100 mg L?1 AZT, suggesting a stimulation of defence cell production. In the liver, the antioxidant enzyme activities did not change, but GST activity and the GSH level increased in fish exposed to 100 mg L?1 AZT. Oxidative stress did not occur. Histopathological index (HIL) indicates moderate liver damage; minor histological changes in the gill and no change in the kidneys. AZT was considered non‐toxic for O. niloticus after acute exposure and, although it causes moderated histopathology in the liver after chronic exposure, this antibiotic may be an alternative against bacterial infections, depending on its efficacy to control bacterial disease in fish.  相似文献   

11.
Epinephelus morio is a large carnivorous species of the Caribbean Sea under reproduction in captivity and nutritional physiology. A diet with raw cornstarch (RCS) was compared to a basal diet without starch (basal) to measure plasma glucose, liver glycogen, and intermediary metabolism. Glucose level did not change (p > 0.05) whereas liver glycogen was significantly higher in fish fed the RCS diet (137.2 ± 14.5 mg g?1) than in fish fed the basal diet (87.4 ± 14.5 mg g?1). Oral glucose administration (170 mg glucose per 100 g body weight) yielded a slight change; two peaks of plasma glucose were recorded with basal (5.6 mM L?1) 2 h after oral administration and at 12 h (6.4 mM L?1). After 24 h, with 1.7 mM L?1, fish returned to initial stage (2.4 mM L?1). RCS diet produced the highest level (6.3 mM L?1) 2 h after oral administration; lowest level observed at 24 h after oral administration (1.0 mM L?1). A significant effect was detected with the presence or absence of dietary carbohydrates (CBH) on hepatic fructose 1,6-bisphosphatase and pyruvate kinase activity. Grouper used two strategies to maintain glucose homeostasis: CBH present in the diet oriented towards gluconeogenesis, whereas no dietary CBH enhanced glycolytic route to liberate glucose and increase liver glycogen.  相似文献   

12.
Regulatory approval is being sought to use praziquantel (PZQ) to treat flukes infecting yellowtail kingfish (YTK), but accurate safety data were not available. We investigated the effect of increased doses or prolonged exposure of orally administered PZQ on YTK by assessing changes in haematological and biochemical characteristics, and mortality. Fish were intubated daily for 3 days with 0, 100, 300 and 500 mg PZQ kg?1 BW day?1 or once daily for 9 days at 0 and 100 mg PZQ kg?1 BW day?1. Blood was taken 24 h after the cessation of treatment. There was no significant difference between any of the haematological or biochemical indices in YTK treated with PZQ and controls, indicating that PZQ is safe for use at 100 mg PZQ kg?1 BW day?1 in YTK and that exposure to high doses or prolonged duration does not have negative effects on the YTK haematological or biochemical parameters we measured.  相似文献   

13.
In this study, loach (Paramisgurnus dabryanus) were fed artificial diets containing 0.31 (control), 0.39, 0.48, 0.50 and 0.62 mg kg?1 of selenium (Se) for 60 days, respectively. Liver histopathology, hepatocyte ultrastructure, blood indices, biochemical parameters of liver functions and oxidative stress in the Se-treated loach were then assayed. The results showed the following: histopathological and ultrastructural lesions in liver were only observed in loach fed the 0.62 mg Se kg?1 diet; Haemoglobin and total protein were significantly increased in the 0.50 mg Se kg?1 group; albumin and high-density lipoprotein were increased significantly in the 0.48–0.50 mg Se kg?1 groups. However, white blood cell count was significantly decreased in the 0.48 mg Se kg?1 group; alanine aminotransferase, aspartate aminotransferase and lactate dehydrogenase were decreased in the 0.39–0.50 mg Se kg?1 groups. In liver tissue, the content of hydrogen peroxide was lower than that of controls in the 0.48–0.50 mg Se kg?1 groups, and the malondialdehyde level was lowest in the 0.48 mg Se kg?1 group. The activities of superoxide dismutase and glutathione peroxidase were significantly increased in the 0.50 mg Se kg?1 group; catalase and total antioxidant capacity were markedly increased in the 0.48–0.50 mg Se kg?1 group. These present results indicated that the dietary Se requirement for loach is 0.48–0.50 mg Se kg?1 diet.  相似文献   

14.
The acute tolerance of juvenile Florida pompano Trachinotus carolinus L. (mean weight±SE=8.1±0.5 g) to environmental unionized ammonia‐nitrogen (NH3‐N) and nitrite‐nitrogen (NO2‐N) at various salinities was determined via a series of static exposure trials. Median‐lethal concentrations (LC50 values) of NH3‐N and NO2‐N at 24, 48, and 96 h of exposure were calculated at salinities of 6.3, 12.5 and 25.0 g L?1 at 28 °C (pH=8.23–8.36). Tolerance of pompano to acute NH3‐N exposure was not affected by salinity, with 24, 48 and 96 h LC50 values ranging from 1.05 to 1.12, 1.00 to 1.08 and 0.95 to 1.01 mg NH3‐N L?1 respectively. Regarding NO2‐N, tolerance of pompano to this environmental toxicant was compromised at reduced salinities. Median‐lethal concentrations of NO2‐N to pompano at 24, 48 and 96 h of exposure ranged from 67.4 to 220.1, 56.9 to 140.7 and 16.7 to 34.2 mg NO2‐N L?1 respectively. The results of this study indicate that juvenile Florida pompano are relatively sensitive to acute NH3‐N and NO2‐N exposure, and in the case of the latter, especially at lower salinities.  相似文献   

15.
Ammonia toxicity and morphological changes in gills of juvenile Japanese flounder Paralichthys olivaceus (5.76 ± 0.12 g) were investigated when fish were separately exposed to normal dissolved oxygen (DO) at 6.5 ± 0.5 mg L?1 and supersaturated oxygen at 16.0 ± 2.0 mg L?1 at different ammonia concentrations. Under normal oxygen, ammonia concentrations were tested from 0.04 (control) to 93.3 mg L?1 total ammonia nitrogen (TAN), whereas under oxygen supersaturation, ammonia concentrations ranged from 0.04 (control) to 226.7 mg L?1 TAN in the trial. After exposure to ammonia for 96 h, the ammonia LC50 for fish was 62.48 mg L?1 TAN (0.50 mg L?1 NH3–N) at normal oxygen and 160.71 mg L?1 TAN (0.65 mg L?1 NH3–N) at oxygen supersaturation. Light microscopic observations confirmed that gill damage in normal oxygen was more profound than in oxygen supersaturation when fish were exposed to the same level of TAN (93.3 mg L?1). Furthermore, electron microscopic scanning also showed more crimple, retraction and fibrosis on the secondary lamella surface in fish exposed to normal oxygen than those in fish exposed to supersaturated oxygen at the same TAN (93.3 mg L?1). This study suggests that supersaturated oxygen can increase ammonia tolerance in Japanese flounder through reducing gill damage by ammonia, which partially explains the merit of using pure oxygen injection in intensive fish farming.  相似文献   

16.
Acute ammonia toxicity was investigated in four developmental stages of the juvenile ide, Leuciscus idus: 1, 10, 20 and 30 days after the first feeding. Mean (±SD) total length of the larvae was 8.5 ± 0.3, 15.7 ± 0.7, 23.0 ± 2.0 and 29.7 ± 2.0 mm, and standard weight was 1.6 ± 0.3, 9.2 ± 5.5, 94.9 ± 31.0 and 196.0 ± 31.7 mg, respectively. The larvae used for toxicity tests were reared in the experimental, closed recirculating system. Groups of fishes (n from 7 to 10; in respect of fish size) were exposed to the ammonium chloride solutions in 1-L glass units. Water temperature was 25 ± 0.1 °C for both the rearing and the toxicity tests. pH was not adjusted and ranged between 8.4 and 8.7. The ammonium chloride solutions were renewed every 12 h. At the same time, dead larvae were counted and removed, and the pH and temperature measurements were taken. Each acute toxicity test duration was 96 h, and lethal concentration LC1, LC50 and LC99 values were calculated for 24, 48, 72 and 96 h. The susceptibility of the ide larvae to ammonia decreased linearly with age up to 20th day and surprisingly increased during the next 10 days. The LC50 (48 h) values ranged from 0.27 mg L?1 of unionized ammonia nitrogen for 1 day after the first feeding (AFF) larvae to 1.42 mg L?1 at day 20 after first feeding. The LC50 (48 h) for 30 days AFF was as high as 0.67 mg L?1. The critical level of the unionized ammonia nitrogen for ide larvae was suggested as 0.21 mg L?1.  相似文献   

17.
Six oxidized fish oil contained diets were formulated to investigate the effect of graded levels of vitamin E (VE) (α-tocopherol acetate: 160, 280, and 400 mg kg?1) associated with either 1.2 or 1.8 mg kg?1 selenium (Se) on growth, body composition, and antioxidant defense mechanism of juvenile largemouth bass. Another control diet containing fresh fish oil with 160 mg kg?1 VE and 1.2 mg kg?1 Se was also prepared. Over a 12-week feeding trial, about 5 % of Micropterus salmoide fed diet OxSe1.2/VE160 showed inflammation and hemorrhage symptoms at the base of dorsal, pectoral, and tail fin. Fish in all treatments survived well (above 90 %). Feed intakes (88.42?89.58 g fish?1) of all treatments were comparable. Growth performances (weight gain and specific growth rate) and feed utilization (feed and protein efficiency ratio) were significantly impaired by dietary oil oxidation, and they did not benefit from neither VE nor Se supplementation. Regardless of dietary VE and Se supplementation, oxidized oil ingestion resulted in markedly decreased hepatosomatic index and intraperitoneal fat ratio. Oxidized oil ingestion also induced markedly lower liver and muscle lipid contents, and these effects could be alleviated by dietary Se supplementation. Dietary oil oxidation stimulated hepatic catalase activities relative to the control, and supplementation of VE abrogated this effect. Hepatic reduced glutathione content in the control was markedly higher than that of treatment OxSe1.2/VE160, without any significant differences comparing with the other oxidized oil receiving groups. Hepatic glutathione peroxidase activity and liver Se concentration reflected dietary Se profile, whereas liver VE level reflected dietary VE profile. Compared with the control, fish fed diet OxSe1.2/VE160 obtained markedly higher serum, liver and muscle malondialdehyde contents, which droppe significantly with increasing either VE or Se supplementation. In conclusion, the overall results in this study suggested that both VE and Se inclusion could protect largemouth bass from the oxidative damage challenged by dietary oil oxidation.  相似文献   

18.
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   

19.
Respiratory parameters of grass carp were studied during dissolved oxygen (DO) changes from normal DO to hypoxia, then return to normal DO at 15, 25, and 30 °C acclimation, respectively. The results showed that with increases of acclimation temperature at normoxia the respiratory frequency (fR), oxygen consumption rate (VO2), respiratory stroke volume (VS.R), gill ventilation (VG), and VG/VO2 of grass carp increased significantly, but the oxygen extraction efficiency (EO2) of fish decreased significantly (P < 0.05). With declines of DO levels, the fR, VS.R, VG, and VG/VO2 of fish increased significantly at different acclimation temperatures (P < 0.05). A slight increase was found in VO2, and the EO2 of fish remained almost constant above DO levels of 3.09, 2.91, and 2.54 mg l?1 at 15, 25, and 30 °C, while the VO2 and EO2 began to decrease significantly with further reductions in DO levels (P < 0.05). After 0.5 h of recovery to normoxia from hypoxia at three acclimation, the fR, VS.R, VG, and VG/VO2 of the fish decreased sharply; meanwhile, the VO2 and EO2 increased sharply (P < 0.05). The respiratory parameters of fish gradually approached initial values with prolonged recovery time to normoxia, and reached their initial values in 2.5 h at 25 and 30 °C acclimation. The critical oxygen concentrations (Cc) of fish for VO2 were 2.42 mg l?1 at 15 °C, 2.02 mg l?1 at 25 °C, and 1.84 mg l?1 at 30 °C, respectively. The results suggest that grass carp are highly adapted to varied DO and short-term hypoxia environments.  相似文献   

20.
This study investigated the effects of the use of the inclusion of açaí on the diet of shrimp Litopenaeus vannamei on antioxidant and histopathological responses after exposure to ammonia. The shrimps were fed two experimental diets: control and with 10% of açaí inclusion (W/W), for 35 days. Afterwards, the organisms were exposed at four concentrations of ammonia (0.01‐control; 0.26; 0.48 and 0.91 mg NH3‐N L?1) for 96 hr. The total antioxidant capacity (ACAP) of the gills decreased significantly in both diets when exposed to ammonia, whereas in the muscle, the açaí promoted an increase in ACAP. Concomitantly, lipid peroxidation levels increased in the gills and decreased in muscle. After exposure to ammonia, glutathione‐S‐transferase activity increased in hepatopancreas in shrimps fed with açaí facilitating the detoxification of lipid peroxidation by‐products, and the concentration of protein sulfhydryl groups decreased in the gills and muscle of the shrimp of the control diet, evidencing protein damage, an unobserved response in shrimps that received the açaí diet. Histopathological changes decreased in açaí‐fed shrimps about the control diet after exposure to ammonia. It is concluded that açaí mitigated ammonia‐induced histopathological changes, improved the antioxidant defence system (gills and muscle) and attenuated the lipid damage in the muscle.  相似文献   

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