Bioaccumulation and toxic effects of copper on growth and oxygen consumption by the postlarvae of Penaeus indicus

The aim of this study was to assess the toxic impact of copper on postlarvae (PL) of the penaeid shrimp Penaeus indicus. Tolerance, growth, oxygen consumption and metal accumulation were investigated in these PL on exposure to copper. Tolerance studies were conducted for 96 h to assess the tolerance limits of P. indicus PL exposed to different concentrations of copper using static renewal bioassay tests. Using the Probit method, the regression equation was calculated as Y=0.4899+2.3562 X, with a correlation coefficient of 0.9707. The 96 h LC₅₀ was 0.8204 ppm. The effect of sublethal (one-fifth of 96 h LC₅₀) copper on PL for short- and long-term exposures revealed a significant (p<0.05) decrease in the rate of oxygen consumption, metabolic rate, mean length, wet and dry weight of the exposed PL over their respective controls which can be attributed to a gradual and time-dependent accumulation of the metal, as noticed in the exposed PL through accumulation studies. Overall, the data suggest that on chronic exposure even sublethal concentrations of copper can reduce the metabolic rate and growth in P. indicus PL. This is perhaps the first attempt to use the wild P. indicus PL as a bioindicator of copper toxicity.     

Impact of malathion on the biochemical parameters of gobiid fish, Glossogobius giuris (Ham)

There is a dearth of information regarding the changes in heart muscle metabolites induced by pesticides. In the present study, the gobiid fish, Glossogobius giuris, was exposed to sub lethal concentrations of (0.05, 0.25 and 0.5 ppm) organophosphorus pesticide, malathion for short duration (24 to 96 hr). The cardiac muscles showed maximum depletion of glycogen and cholesterol content during 72 and 96 hr after treatment with 0.5 ppm malathion. Whereas a slight fluctuation of protein and glycogen content was observed in low concentration (0.05 ppm) of malathion. The levels of protein showed a significant decrease at high concentration (0.5 ppm) when treated for longer duration (96 hr). The present study reports metabolic dysfunction in response to malathion toxicity in the fish.     

Effects of ammonia, nitrite and nitrate on hemoglobin content and oxygen consumption of freshwater fish, Cyprinus carpio (Linnaeus)

Lethal effects of nitrogenous compounds ammonia, nitrite and nitrate on freshwater fish Cyprinus carpio were studied and the static LC50 values obtained for these 3 toxicants for 24 hr were 0.80 ppb, 171.36 ppm; 1075.10 ppm and continuous flowthrough LC50 values for 24 hr were 0.72 ppb, 154.31 ppm; 967.63 ppm respectively. The fish were exposed to lethal concentrations to study the changes in hematological parameters and the rate of oxygen consumption. During the period of exposure general decline in the content of hemoglobin was observed. Methemoglobin content increased in case of nitrite exposure consequently the hemoglobin levels decreased drastically. It is also observed that rate of oxygen consumption decreased progressively with the increase of toxicant concentration and duration of the exposure.     

Effects of copper and cadmium on osmoregulation and oxygen consumption in two species of estuarine crabs

Green crabs (Carcinus maenas) and rock crabs (Cancer irroratus) were exposed to various concentrations of copper as cupric chloride (CuCl₂ · 2 H₂O), and cadmium as cadmium chloride (CdCl₂ · 21/2 H₂O) for 48 h. The exposures were conducted at 5 different salinities. At the end of each exposure period, tests of blood-serum osmolality and gill-tissue oxygen consumption were performed. Copper-exposed crabs exhibited loss of osmoregulatory function with increasing copper concentration until normally hyperosmotic serum became isosmotic with the surrounding medium. Cadmium elevated greencrab serum above its normal hyperosmotic state. Copper had no effect on gill-tissue oxygen consumption; however, cadmium reduced the rate of oxygen consumption in both species tested.     

Influence of environmental salinity on oxygen consumption and ammonia excretion of the arctic under-ice amphipodOnisimus glacialis

Changes in salinity affect the metabolic rate of the sympagic amphipodOnisimus glacialis collected from the Barents Sea in 1986 and 1988. When transferred from 35 to 5 ppt S, oxygen consumption and ammonia excretion both increase three-fold during the first 5 h of exposure, and they remain high throughout the rest of the experimental period (26 h). During 24-h acclimation to various salinities (5 to 45 ppt), the amphipods exhibit a respiratory and excretory response to hyper- and hypoosmotic stress; however, a rather constant O:N atomic ratio (around 15) was obtained at the experimental salinities, indicating protein/lipids as metabolic substrate. Both rates of oxygen consumption and ammonia excretion increased with an increasing osmotic difference (0 to 650 mOsm) between the haemolymph and the environmental medium, indicating higher energy requirements for osmotic and ionic regulation at low salinities. In amphipods abruptly transferred from 35 to 5 ppt, a minor decrease of the haemolymph sodium concentrations together with an increased ammonia excretion output indicate a counter-ion regulation of NH ₄ ⁺ and Na⁺ during hyposmotic stress.     

Respiration,pumping activity and heart rate in Ciona intestinalis exposed to fluctuating salinities

Specimens of Ciona intestinalis L. were exposed to both gradual (sinusoidal) and abrupt (square-wave) salinity fluctuations and the changes in pumping activity and oxygen sonsumption monitored. Heart rate was monitored under steady state conditions using a new in vivo method, and pumping activity was monitored as spontaneous squirting by use of a pressure transducer. Oxygen consumption was also monitored under steady state conditions and under conditions of declining oxygen tension. It was found that during periods of regular beating the mean heart rate for 5 ascidians was 13.2 beats min^-1 for the branchial pacemaker and 32.6 beats min^-1 for the visceral pacemaker. Regular periods of beating lasted for approximately 1 min, followed by periods of irregular activity prior to heart beat reversal. The heart beat became irregular and reversal occurred sporadically when the ascidians were exposed to dilute seawater. The ascidians showed a pumping rate of 14 squirts per hour in full-strength seawater. This rate declined during decreasing salinity and ceased entirely when the external seawater concentration reached approximately 60% seawater (100%=32% S). During periods of decreased salinity, the siphons were tightly closed and oxygen consumption was zero. The rate of oxygen consumption by C. intestinalis decreased during decreasing salinities and there was no evidence of an oxygen debt. Oxygen consumption under steady state conditions varied with body weight according to the following: oxygen consuption =0.515 W ^0.831 (where W is body weight). The rate of oxygen consumption was found to be dependent on the external oxygen tension.     

Individual effects and interactions of salinity,temperature, and zinc on larval development of the grass shrimp Palaemonetes pugio. I. Survival and developmental duration through metamorphosis

Larvae of the estuarine grass shrimp Palaemonetes pugio (Holthuis) were reared from hatch through successful completion of metamorphosis in 80 combinations of salinity (3 to 31%), temperature (20° to 35°C), and zinc (0.00 to 1.00 ppm Zn⁺⁺). Response-surface methodology was employed to depict the individual effects and interactions of the three factors on survival and developmental duration through total larval development. Outside the optimal salinity-temperature conditions of 17 to 27 S and 20° to 27°C, viability of larvae was reduced by both the individual effects of salinity and temperature and interactions between the two factors. Survival capacity of larvae and resistance adaptations to salinity and temperature were progresively reduced by zinc concentrations from 0.25 to 1.00 ppm Zn⁺⁺. Response-surface analysis of the data suggested that the duration of total larval development of P. pugio was least at salinities from 18 to 23 and at temperatures from 30° to 32°C. At both higher and lower salinity-temperature conditions and in increasing zinc concentrations from 0.25 to 1.00 ppm Zn⁺⁺, developmental rates were retarded. A significant zinc-temperature interaction existed, whereby increasing zinc concentrations reduced both survival and developmental rates of larvae more at suboptimal temperatures. Larval resistance to zinc toxicity was least at supraoptimal salinities, indicative of a significant zinc-salinity interaction. The reduced viability, restricted euryplasticity, and retarded developmental rates of P. pugio larvae developing in media with low-level zinc contamination would limit the distributive properties of the pelagic phase in the life cycle of the species and reduce recruitment both into and out of the parent estuarine population.     

The effect of copper and zinc on the metabolism of the mussel Mytilus edulis

The effects of copper and zinc on the metabolism of the mussel Mytilus edulis (L.) and its component tissues were studied. 500 ppm copper sodium citrate inhibited oxygen consumption of the whole animal and gill tissue, but no similar effect was observed on digestive gland tissue. 500 ppm zinc sodium citrate exerted no effect upon gill or digestive gland respiration, and neither metal salt affected the respiration of homogenates of gill, digestive gland or gonad. Direct observation of gill tissues during exposure to the metals revealed that 500 ppm copper sodium citrate caused inhibition of ciliary activity; exposure of tissues to 2 ppm Cu for 24 h resulted in only partial inhibition of the cilía. It is suggested that metabolic suppression noted in whole animals and gill tissues is due to the inhibition of an energy-consuming process such as ciliary activity rather than interference with respiratory enzyme systems.     

Simultaneous, long-term monitoring of valve and cardiac activity in the blue mussel Mytilus edulis exposed to copper

Valve and cardiac activity were simultaneously measured in the blue mussel (Mytilus edulis) in response to 10?d copper exposure. Valve movements, heart rates and heart-rate variability were obtained non-invasively using a Musselmonitor^® (valve activity) and a modified version of the Computer-Aided Physiological Monitoring system (CAPMON; cardiac activity). After 2?d exposure of mussels (4 individuals per treatment group) to a range of dissolved copper concentrations (0 to 12.5?M as CuCl₂) median valve positions (% open) and median heart rates (beats per minute) declined as a function of copper concentration. Heart-rate variability (coefficient of variation for interpulse durations) rose in a concentration-dependent manner. The 48?h EC₅₀ values (concentrations of copper causing 50% change) for valve positions, heart rates and heart-rate variability were 2.1, 0.8, and 0.06?M, respectively. Valve activity was weakly correlated with both heart rate (r?=?0.48?±?0.02) and heart-rate variability (r?=?0.32?±?0.06) for control individuals (0?M Cu²⁺). This resulted from a number of short enclosure events that did not coincide with a change in cardiac activity. Exposure of mussels to increasing copper concentrations (≥0.8?M) progressively reduced the correlation between valve activity and heart rates (r?=?0 for individuals dosed with ≥6.3?M Cu²⁺), while correlations between valve activity and heart-rate variability were unaffected. The poor correlations resulted from periods of valve flapping that were not mimicked by similar fluctuations in heart rate or heart-rate variability. The data suggest that the copper-induced bradycardia observed in mussels is not a consequence of prolonged valve closure.     

Life table demography of Ceriodaphnia dubia (Cladocera) exposed to copper at different levels and periods

We studied the demographic responses of Ceriodaphnia dubia exposed to copper at 3 different levels (0.1, 0.2 and 0.4 mg l(-1)) and at 4 exposure periods (3, 6, 12 and 24 hr) in addition to controls (without the heavy metal). The tested levels of Cu concentration and the chosen periods of exposure affected some demographic variables (average lifespan, gross and net reproductive rates and generation time). Depending on the heavy metal concentration and the period of exposure, the average lifespan of C. dubia varied from 18 to 24 day Net reproductive rates (NRR) ranged from 50 to 80 offspring per female per lifespan, while the rate of population increase (r) varied from 0.30 to 0.34 per day Though gross reproductive rates (especially at low and intermediate copper levels and shorter duration of exposure) showed significantly higher values than controls, both NRR and r were either unaffected or decreased. It is therefore necessary to regulate the release of untreated industrial effluents containing copper into freshwater ecosystems. Our study thus highlights the importance of including, not only toxicant concentrations but also exposure time, in ecotoxicological evaluations.     

Metabolic rates of epipelagic marine copepods as a function of body mass and temperature

Metabolic rates (oxygen consumption, ammonia excretion, phosphate excretion) have been calculated as a function of body mass (dry, carbon, nitrogen and phosphorus weights) and habitat temperature, using multiple regression. The metabolic data used for this analysis were species structured, collected from Arctic to Antarctic seas (temperature range: -1.7°C to 29.0°C). The data were further divided into geographical and/or seasonal groups (35 species and 43 data sets for oxygen consumption; 38 species and 58 data sets for ammonia excretion; 22 species and 31 data sets for phosphate excretion). The results revealed that the variance attributed to body mass and temperature was highest (93-96%) for oxygen consumption rates, followed by ammonia excretion rates (74-80%) and phosphate excretion rates (46-56%). Among the various body mass units, the best correlation was provided by the nitrogen unit, followed by the dry weight unit. The calculated Q₁₀ values varied slightly according to the choice of body mass units; overall ranges were 1.8-2.1 for oxygen consumption rates, 1.8-2.0 for ammonia excretion rates and 1.6-1.9 for phosphate excretion rates. The effects of body mass and temperature on the metabolic quotients (O:N, N:P, O:P) were insignificant in most cases. Although the copepod metabolic data used in the present analysis were for adult and pre-adult stages, possible applications of the resultant regression equations to predict the metabolic rates of naupliar and early copepodite stages are discussed. Finally, global patterns of net growth efficiency [growth (growth+metabolism)^-1] of copepods were deduced by combining the present metabolic equation with Hirst and Lampitt's global growth equation for epipelagic marine copepods.     

Histopathological alterations of Nile tilapia, Oreochromis niloticus in acute and subchronic alachlor exposure

Histopathological alterations in Nile tilapia, Oreochromis niloticus, aged 3 months and subjected to acute and subchronic alachlor exposure were studied by light microscopy LC50 values of alachlor for 24 hr 48 hr, 72 hr and 96 hr were 963.6, 563, 448, and 381.9 microg l(-1), respectively and the maximum acceptable toxicant concentration (MATC) was 350 microg l(-1). Fish were exposed to 381.9 (acute) and 35 microg l(-1) (sub-chronic) of alachlor for 24, 48, 72 and 96 hr and 90 days, respectively Gill lamellae and kidney tubules were the primary target organs for the acute toxic effect of alachlor while in the subchronic exposure, the toxic effect on the gills was less marked than that of the kidneys and liver Gill alterations included edema of the epithelial cell system, aneurisms with some ruptures, hypertrophy and hyperplasia of epithelial cells. The liver showed hydropic swelling of hepatocytes and vacuolation. Lipid vacuoles were observed in hepatocytes in the second and third month of subchronic exposure. The kidney showed hydropic swelling of tubular cells, lipid vacuole accumulation in many tubules, and nuclear pyknosis. The findings of this study could be used as a guideline forbiomonitoring programs on populations of Nile tilapia cultured near alachlor contaminated areas.     

Comparative study of the effects of temperature,salinity and oxygen tension on the rates of oxygen consumption of nauplii of different strains of Artemia

The effects of temperature, salinity and oxygen tension on the rates of oxygen consumption of three different strains of Artemia nauplii have been studied. When acclimated to a salinity of 30, nauplii from each of the three strains were able to maintain approximately constant rates of oxygen consumption over a wide range of oxygen tension. The ability to maintain respiratory independence during hypoxia was reduced, however, with an increase in either temperature or salinity. Nauplii of two of the strains (parthenogenetic diploid and tetraploid) showed a progressive increase in the rate of oxygen consumption with increasing temperature up to 35°C. Nauplii of the bisexual strain appeared to be less tolerant of exposure to temperatures >30°C, since at higher temperatures their oxygen consumption declined slightly. The differences between the nauplii of the different strains in their physiological responses to changing environmental conditions appear to correlate well with their seasonal occurrence in the field.     

Influence of salinity and temperature on the oxygen consumption in young juveniles of the Indian prawn Penaeus indicus

Routine oxygen consumption of very young juveniles (0.1 g) of Penaeus indicus H. Milne Edwards was significantly influenced by ambient temperature and weight of the animal, but not by ambient salinity, when tested at salinities (7, 21, and 35) to which they had been long-term (over 10 days) acclimated. Standard oxygen consumption of young juvenile prawns (1 to 3 g), subjected to step-wise changes in ambient salinity, from sea water to low salinity waters (2 to 6), and measured after short-term (24 h) salinity acclimation at each step, was lowest at salinities where prawns such as those tested occur naturally (10 to 15). The metabolic rates do not appear to have a direct relation to the osmotic gradient, even when the influence of interfering activity is eliminated. It appears that factors other than osmotic gradient will have to be sought in order to explain the metabolic patterns of P. indicus in relation to salinity.     

Developmental arrest in Japanese medaka (Oryzias latipes) embryos exposed to sublethal concentrations of atrazine and arsenic trioxide

Embryos of the Japanese medaka (Oryzias latipes) were exposed to serial concentrations of atrazine (0, 25, 50, and 100 ppm) and arsenic trioxide (0, 0.025, 0.05, 0.1 ppm) until hatching. Stasis of circulation, blood islands, titanic convulsions, tube heart and mortality were observed in atrazine-treated embryos. Each endpoint exhibited a concentration-response relationship. Only 4% of the embryos hatched in the 25 ppm, and none in the 50 and 100 ppm, probably due to cell death attributed to the embryos' inability to break from the chorion. With arsenic exposure, hatching was inversely correlated to chemical concentration: 86%, 75% and 54% for 0.025, 0.05 and 0.1 ppm, respectively. Hatching periods were also reduced from 7-13 days in controls to 7-11 days in arsenic-treated embryos. This observation was more pronounced with the 0.05 ppm concentration, showing a reduction of about 4 days. Despite this shortage in hatching time, there were no observable morphological abnormalities, as seen with atrazine. The ecological significance of these findings and implications for the development of sublethal toxicity tests using Japanese medaka embryos are important.     

Tertiary-butyl acetate metabolism,toxicity, and human health considerations

Tertiary-butyl acetate (TBAC) (CAS No. 540-88-5) is an organic solvent with a potential for occupational and environmental exposure as a result of its use in industrial coatings, adhesives, inks, and degreasers. The objective of these studies was to extend the toxicological database upon which health hazard and risk assessments of TBAC can be made. The metabolism of TBAC was studied in rats exposed by inhalation for 6?h to concentrations of 100 or 1000?ppm. There was an evidence of partial saturation of TBAC absorption and metabolism at some concentration below 1000?ppm. Approximately 5% of the low dose and 26% of the high dose was expired without change within 12?h, while the retained material was rapidly metabolised and excreted, mostly in the urine, within 24?h. Very little radioactivity remained in the tissues after day 7. The metabolism of TBAC appears to follow two major routes: hydroxylation of the tertiary-butyl moiety to form 2-hydroxymethylisopropyl acetate and ester hydrolysis to form tertiary-butyl alcohol (TBA). A minor route involves oxidation of the acetate moiety. Based on the proportion of metabolites that can clearly be assigned to one or the other major pathway, hydroxylation of the tertiary-butyl moiety prevails at 100?ppm, while hydrolysis of the ester bond predominates at 1000?ppm.

Based on nose-only inhalation exposure of rats to TBAC for 6?h, the LC50 for males and females combined is approximately 4200?ppm. Clinical signs included exaggerated breathing, staggering, tremors, and lethargy approximately 1?h after the exposure, but all surviving rats appeared normal from 24?h until the end of the 14?day observation period. An LC₅₀ was not identified for mice. After exposure of whole body for 6?h to 3000?ppm, the highest concentration tested, all mice were prostrate for most of the exposure time, but there were no deaths.

Groups of five male and five female Sprague-Dawley rats were exposed nose-only to 0, 100, 400, or 1600?ppm TBAC 6?h?day^?1 5 days?wk^?1 for 2?weeks. There were no effects on body weight, feed or water consumption, or necropsy findings. Male rats exposed to 1600?ppm had increased liver weights and hypertrophy of centrilobular hepatocytes. An increased proportion of cortical tubule cells with hyaline droplet accumulation was observed in all treated groups of males. Groups of five male and five female CD-1 mice were exposed whole body to 0, 190, 375, 750, or 1500?ppm TBAC 6?h?day^?1 for 14 consecutive days. There were no effects on body weight, feed consumption, or necropsy findings. Liver weights were increased in female mice at 750 and 1500?ppm. Minimal hypertrophy of centrilobular hepatocytes was found in female mice at 375, 750, and 1500?ppm and in male mice at 1500?ppm TBAC.

TBAC did not induce gene mutations in bacterial tests with strains of S. typhimurium and E. coli. Further, there was no evidence of clastogenic activity from tests either for the induction of chromosomal aberrations in human lymphocytes in vitro in the presence or absence of S9 mix or for the induction of micronuclei in bone marrow cells of rats exposed by inhalation for 6?h to 1600?ppm TBAC.

These results are relevant to human health risk assessment and are discussed in the context of previous studies. The weight of the scientific evidence supports the conclusion that TBAC has lower acute toxicity than previously suggested, that it is rapidly excreted when inhaled, and that neither TBAC nor its TBA metabolite are genotoxic or potential human carcinogens.     

Effects of chronic copper exposure on the green mussel Perna viridis

The effects of chronic copper exposure on growth and physiological responses of the green mussel Perna viridis were investigated by exposing the mussels to 50 μg l⁻¹ Cu for 3 mo at 17 and 25 °C. These temperatures represent, respectively, the winter and summer seawater temperatures in Hong Kong. Differences in the level of response between mussels exposed for 3 mo to 50 μg Cu l⁻¹ generally increased with duration of exposure. The tissue concentration of copper had increased by 280 and 450% after 3 mo exposure at 17 and 25 °C, and growth performances were reduced, with the 25 °C sets suffering from larger negative impact of copper in most responses. The inhibitory effects of copper on production of the various body components generally followed the order linear shell growth (greatest) > tissue production > byssus production > shell production. There were also decreases in the condition index (43 and 35% reductions at 17 and 25 °C), clearance rates (10.3 and 18.5%), faeces production (11 and 16.3%), assimilation efficiency (6.8 and 9.2%) and oxygen consumption rate (12.8 and 24.8%). In contrast, the organic content of the faeces (9.2 and 13.2% increases at 17 and 25 °C) and rate of ammonia excretion (21 and 28.6%), increased upon chronic copper exposure. Many of the responses (e.g. changes in tissue copper content, body dry wt, shell organic content, clearance rate and oxygen consumption rate) exhibited fluctuating levels of impact during prolonged copper exposure, while others (e.g. faecal production rate, assimilation efficiency, tissue organic content) demonstrated steady decreasing trends with increasing exposure time. Received: 17 September 1999     

Effect of copper on ion- and osmoregulation in the shore crab Carcinus maenas

The uptake and effect of dissolved copper on regulation of hemolymph osmolality and Na⁺, K⁺, Cl^-, Ca⁺⁺, and Mg⁺⁺ concentrations in the shore crab Carcinus maenas (L.) were determined at 400 mOsm (=14 S) ambient salinity. One mg Cu l^-1 resulted in 50% mortality in 11 to 22 d; the highest sensitivity was observed around the moulting period. 0.25 and 0.5 mg Cu l^-1 were not lethal after a onemonth exposure. Ten, 1, and 0.5 mg Cu l^-1 altered regulation of osmolality, Na⁺, K⁺, and Cl^- concentrations, while 0.25 mg Cu l^-1 did not. Exposure to 1 mg Cu l^-1 reduced hemolymph osmolality and Na⁺, K⁺, and Cl^- concentrations to 80 to 90% of controls within 4 to 6 d and no further reduction was observed during a 21-d exposure. The effect of various copper concentrations on these four parameters were almost identical and the highest sensitivity was observed around the moulting period. Hemolymph calcium levels increased 20 to 80% in crabs exposed to 1 mg Cu l^-1, while they decreased 20 to 30% in crabs exposed to 0.5 mg Cu l^-1. Prolonged exposure to copper caused 20 to 70% reductions in hemolymph magnesium levels. Crabs exposed to 0.5 mg Cu l^-1 for 29 d accumulated copper in hepatopancreas, gills, carapace, heart, testes, and hypodermis, but not in muscles and hemolymph. Increased copper levels in crabs exposed to 0.25 mg Cu l^-1 were observed in hepatopancreas, gills, and carapace only. The present results suggest that effects of copper on ion regulatory processes in part explain why the toxicity of copper towards euryhaline invertebrates increases at low salinities.     

铅暴露与排放对中华鲟幼鱼血液中ALT、AST活力的影响

采用水溶液静态置换法,从中华鲟(Acipenser sinensis)受精卵发育至96 h开始,研究了其在0(对照组)、0.2、0.8和1.6mg·L~(-1) Pb~(2+)水溶液中暴露16周,随后排放6周,对中华鲟幼鱼血液中ALT、AST活力的影响.结果显示:Pb暴露后幼鱼血液中的ALT和AST活力均表现为随Pb暴露剂量增加而升高的趋势,1.6mg·L~(-1)组ALT活力与其它各组比较呈极显著差异(P<0.01);0.8和1.6mg·L~(-1)组AST活力与对照组比较分别呈显著差异(P<0.05)和极显著差异(P<0.01). Pb排放后,各暴露组血液中ALT活力降低至对照组水平(P>0.05);1.6 mg·L~(-1)组的AST活力依然较高.超出对照组近2倍(P<0.01).对照组血液的AST/ALT值在2.24～2.32之间;随Pb质量浓度增加,暴露后AST/ALT值呈增加趋势.Pb排放后AST/ALT值降低,但1.6 mg·L~(-1)组与其余各组比较仍维持较高值(P<0.05).初步认为,0.2 mg·L~(-1)和0.8 mg·L~(-1) Pb~(2+)暴露导致中华鲟幼鱼肝细胞不同程度受损,经Pb排放后,轻度受损的组织细胞能够恢复.血液中的AST/ALT值在判断鱼类组织损伤中也具有重要意义.     

乙酸铜对银鲳幼鱼急性毒性及抗氧化酶活性的影响

为评价乙酸铜对银鲳的安全性及毒性效应,采用静水急性暴露实验,研究了8个乙酸铜浓度梯度(0、0.150、0.206、0.282、0.387、0.531、0.729、1.00 mg·L~(-1))对银鲳幼鱼的急性毒性,以肝脏和鳃组织的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化酶(GSH—PX)以及谷胱甘肽巯基转移酶(GST)活性为指标研究乙酸铜对银鲳幼鱼的毒理作用,并进行安全评价。结果表明,高浓度乙酸铜会对银鲳幼鱼产生了较大的毒性,48 h和96 h-LC_(50)分别为0.898 mg·L~(-1)、0.264 mg·L~(-1),安全质量浓度为0.026 mg·L~(-1);不同浓度乙酸铜胁迫下银鲳幼鱼组织中的SOD、CAT、GSH-PX和GST活性均表现为低浓度被诱导而高浓度受抑制的规律,与乙酸铜浓度呈抛物线型剂量效应关系,此外,肝脏中4种抗氧化酶活性普遍高于鳃组织。研究发现,乙酸铜胁迫对抗氧化酶的影响,可以反映银鲳幼鱼机体的受损状况,其中SOD可较灵敏地指示早期低浓度的铜污染。