Sublethal Zinc and Copper Exposure Affect Acetylcholinesterase Activity and Accumulation in Different Tissues of Leporinus obtusidens

In this study, we investigated zinc and copper effects on acetylcholinesterase (AChE, EC. 3.1.1.7) activity and metal accumulation in tissues of native fish Leporinus obtusidens (piava). Fish were exposed to 10 and 20 % of the LC₅₀ that corresponded at 2.28 and 4.57 mg/L (zinc) and 0.018 and 0.038 mg/L (copper) for 30 and 45 days. The AChE activity was evaluated in brain and white muscle of fish and metals accumulation was measured in kidney, liver, muscle and brain. Exposure to zinc and copper significantly increased AChE activity in both tissues and times tested, except for brain AChE activity at 2.28 mg/L of Zn (II) after 45 days where a reduction of 52.5 % was observed. Fish exposed to zinc showed accumulation of this metal in liver and kidney in both concentrations and times tested. A different result was obtained for copper: significant copper accumulation was obtained only in brain at both concentrations tested after 45 days of exposure. These results suggest that piavas exposed to zinc and copper showed changes in AChE activity and also demonstrate accumulation in some tissues. These results demonstrate that L. obtusidens could be a good bioindicator to evaluate water containing metals. The metal accumulation absence in muscle tissue is an indicative of low potential contamination by metals in this fish species.     

Exposure to a Commercial Glyphosate Formulation (Roundup<Superscript>®</Superscript>) Alters Normal Gill and Liver Histology and Affects Male Sexual Activity of <Emphasis Type="Italic">Jenynsia multidentata</Emphasis> (Anablepidae,Cyprinodontiformes)

Roundup is the most popular commercial glyphosate formulation applied in the cultivation of genetically modified glyphosate-resistant crops. The aim of this study was to evaluate the histological lesions of the neotropical native fish, Jenynsia multidentata, in response to acute and subchronic exposure to Roundup and to determine if subchronic exposure to the herbicide causes changes in male sexual activity of individuals exposed to a sublethal concentration (0.5 mg/l) for 7 and 28 days. The estimated 96-h LC₅₀ was 19.02 mg/l for both male and female fish. Gill and liver histological lesions were evaluated through histopathological indices allowing quantification of the histological damages in fish exposed to different concentrations of the herbicide. Roundup induced different histological alterations in a concentration-dependent manner. In subchronic-exposure tests, Roundup also altered normal histology of the studied organs and caused a significant decrease in the number of copulations and mating success in male fish exposed to the herbicide. It is expected that in natural environments contaminated with Roundup, both general health condition and reproductive success of J. multidenatata could be seriously affected.     

Adaptation to soil pollution by cadmium excretion in natural populations of Orchesella cincta (L.) (Collembola)

Population differentiation in Orchesella cincta (L.) (Collembola) populations, from various heavy metal contaminated sites, was studied by comparing cadmium excretion efficiency in first generation (F₁) laboratory individuals. Animals from sites with high metal concentrations in the litter and with a long history of contamination showed significantly higher excretion efficiencies than animals from low pollution, or reference sites. Differences found in the F₁ laboratory animals suggest evidence for genetic differences between the populations.Beneficial and detrimental effects of cadmium excretion were studied in relation to body growth and cadmium concentrations. In chronically exposed animals from an unpolluted site, no physiological acclimation was observed. Excretion efficiency was negatively correlated with body concentrations of cadmium. No detrimental effects were found.Whole-body equilibrium concentrations of cadmium and lead were similar in F₁ animals from the reference site and polluted sites. Significant differences in excretion efficiencies imply that the distribution of toxic metals over body compartments differs, tolerant populations having a higher proportion deposited in the gut. Body concentrations of zinc were consistently higher in animals from the polluted site, during both cadmium and zinc exposure. No detrimental effects of increased cadmium excretion on body concentrations of zinc were observed. Population comparisons of cadmium excretion efficiency data and growth reduction in F₁ laboratory animals showed that both parameters were inversely related. Cadmium and lead contamination were not the sole factors determining tolerance differentiation.     

Antioxidant responses, hepatic intermediary metabolism, histology and ultrastructure in Synechogobius hasta exposed to waterborne cadmium

The present study was conducted to determine antioxidant responses, hepatic intermediary metabolism, histology and ultrastructure in Synechogobius hasta after a 15-days of waterborne cadmium (Cd) exposure at the concentrations of 0 (control), 0.10, 0.17 and 0.29 mg Cd/l (corresponding to 0, 12.6%, 21.5% and 36.7% of 96 h LC₅₀), respectively. Growth performance and survival declined, but hepatosomatic index (HSI) increased with increasing waterborne Cd levels (P<0.05). Waterborne Cd exposure also significantly increased lipid contents in whole body and liver (P<0.05), and Cd accumulation in whole body, muscle and vertebrae. Waterborne Cd exposure changed hepatic enzymatic activities involved in intermediary metabolism, induced antioxidant responses and increased lipid peroxidation level in the gill, liver and spleen. Waterborne Cd exposure also caused considerable histological alterations of gill, liver and spleen, led ultrastructures damage of liver and spleen of fish, and induced fatty liver for this fish species.     

Assessing the risk of metal mixtures in contaminated sediments on Chironomus riparius based on cytosolic accumulation

Sediments usually contain mixtures of trace metals introduced via natural geochemical processes and anthropogenic activities. Kinetics and effects of these metals are strongly dependent both on the composition of the mixture and on the physico-chemical characteristics of the sediment. Relating effects to metal concentration may consequently be advised. However, total accumulation may be a poor predictor of metal toxicity for Chironomus riparius exposed to contaminated field sediments. As an alternative, we proposed to relate effects on Chironomus growth with cytosolic metal accumulation, measured in larvae after a short exposure period. Dose–response relationships were derived for zinc, copper, and cadmium through single-metal exposure data analysed with toxicokinetics and toxicodynamics models. They permitted, on the basis of cytosolic accumulation measures, to predict successfully the effects of mixtures of cadmium, zinc, and copper on the growth of larvae exposed to spiked sediments, as well as to field sediments in which zinc and copper were assumed to be predominant.     

Biochemical Composition, Growth, and Survival of the Guppy, Poecilia reticulata, During Chronic Sublethal Exposure to Cadmium

The survival, growth, and biochemical composition (protein, total lipid, total carbohydrate, free reducing sugars, RNA, DNA) of the guppy, Poecilia reticulata, exposed to low sublethal concentrations of cadmium throughout its life cycle (beginning with 5-day-old juveniles) was studied. The purpose was to get some insight on the cause of metal toxic effects and evaluate the utility of monitoring levels of biomolecules as bioindicators of chronic toxicant effects on fish. The LC₅₀ (48 h) of cadmium for 5-day-old Poecilia was 56.77 mg/L. The median lethal times (LT₅₀) of Poecilia exposed to low cadmium concentrations (0.5–5 mg/L) ranged from 7.65 to 72.51 days, and could be accurately predicted by the mortality observed after 20 days of exposure. The whole-body dry weight increase of cadmium-exposed guppies presented a decline from that of the controls. These declines were statistically significant after 20 days of exposure to concentrations higher than 1 mg/L and after 30 days to concentrations higher than 0.5 mg/L. The percentage content in RNA was the only variable from the studied macrobiomolecules that significantly decreased when guppies were exposed to Cd concentrations higher than 0.5 mg/L for 30 days. The same trend was apparent in the ratio RNA/DNA. However, the ratio protein/RNA/DNA significantly increased after 10 days of growth to 1.5 mg/L and after 20 days to concentrations higher than 0.5 mg/L, thus having a predictive value for early-life history stages of Poecilia exposed to Cd. Received: 15 May 1997/Accepted: 6 January 1998     

Effect of humic acid during concurrent chronic waterborne exposure of rainbow trout (Oncorhynchus mykiss) to copper, cadmium and zinc

The effects of commercial dissolved organic carbon (DOC) in moderating accumulation, biochemical responses and toxicity of a waterborne mixture of copper (Cu), cadmium (Cd) and zinc (Zn) were investigated during a chronic exposure. Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to a ternary metals mixture containing (nominal concentrations in μg/l): Cu 30, Cd 15, and Zn 150 in hard water (260 mg/l as CaCO₃) with and without addition of 5 mg/l DOC as Aldrich humic acid (HA) for 28 days. Mortality, growth, metals accumulation, ionoregulatory impairment, and oxidative stress response were measured. While growth was unaffected, 19% mortality occurred during the first week of the exposure in fish exposed to the metals mixture without added HA. The early mortality was associated with transitory whole-body sodium (Na) loss and inhibition of branchial Na⁺, K⁺-ATPase activity. Although these ionoregulatory responses mechanistically suggested that Cu was the more potent toxicant than either Cd or Zn, they were not correlated uniquely with elevated tissue Cu concentrations. The effects of HA on accumulation were metal-specific and depended on the organ examined and exposure duration. Specifically, Zn accumulation occurred only in the gill early in the exposure and HA reversed it, while protection against accumulation was absent or complete for Cu and absent or partial for Cd, dependent on tissue and exposure duration. The computed ambient free metal ion activities could explain the Cd but not the Cu and Zn accumulation indicating the involvement of physiological regulatory mechanisms in defining accumulation of essential metals. Surprisingly, the metals mixture (with and without added HA) reduced the concentrations of malondialdehyde (MDA) in gill suggesting induction of reductive rather than oxidative stress. Overall these data indicate that the free metal ion activity alone is not universally a good predictor of metals mixture accumulation and chronic effects nor does consideration of the mechanisms of toxicity unambiguously identify the more potently toxic metal in a mixture.     

Metal Kinetics and Respiration Rates in F1 Generation of Carabid Beetles (Pterostichus oblongopunctatus F.) Originating From Metal-Contaminated and Reference Areas

We investigated resistance to metals in carabid beetles inhabiting metal-polluted and reference areas. Chronic multigeneration exposure to toxic metal concentrations may potentially result in adaptation through decreased metal uptake rate and/or increased excretion rate. The cost of resistance to pollution could be associated with increased metabolic rate. To test these predictions, laboratory cultured F₁-generation beetles originating from metal-polluted and reference sites were exposed to food contaminated with zinc and/or cadmium for 10 weeks. After that, uncontaminated food was offered to the animals for another 3 weeks. During the experiment, internal concentrations of Cd and Zn were measured as were respiration rates of the animals. The results obtained show no significant differences in metal accumulation and excretion patterns or respiration rates between the populations. This may suggest that adaptation has not occurred in the beetles chronically exposed to toxic metal concentrations. The possible explanations for the lack of differences between the populations are discussed.     

Effect of short-term ethanol administration on cadmium retention and bioelement metabolism in rats continuously exposed to cadmium

The present study was performed to assess the effect of short-term ethanol administration on cadmium retention and accumulation as well as on bioelement metabolism (zinc, copper, calcium, and magnesium) in rats exposed to an aqueous solution of cadmium chloride for 8 weeks. Intoxication with cadmium led to accumulation of this toxic metal, particularly in the liver and kidney, which was linked to metallothionein synthesis as well as to a disturbance in the metabolism of zinc, copper, and calcium. These effects were dependent on the level of exposure. The administration of ethanol in the final phase of cadmium treatment increased cadmium retention and accumulation in the body with simultaneous elevation in liver and kidney metallothionein concentration. Ethanol alone or with cadmium caused or intensified the cadmium-induced changes in metabolism of zinc and copper. Calcium metabolism disturbed by cadmium was not influenced by ethanol. Neither agents had any effect on magnesium metabolism. We conclude that even short-term ethanol consumption in conditions of exposure to cadmium can increase this heavy metal body burden and lead to more serious disturbances in metabolism of important elements such as zinc and copper. Cadmium- and ethanol-induced changes in the homeostasis of these microelements are probably connected with the ability of both xenobiotics to cause metallothionein induction.     

Behavioral Responses of <Emphasis Type="Italic">Daphnia Magna</Emphasis> to Stresses of Chemicals with Different Toxic Characteristics

Behavior of an organism is affected by exposure to toxic chemicals. However, less has been known about behavioral responses of an organism to stresses of toxic chemicals with different toxic characteristics. In present work, Daphnia magna Straus was exposed to gradient concentrations of deltamethrin, chlorothalonil and nitrofen and the behavioral changes of Daphnia magna under different stress were examined. The results showed that the behavioral responses of Daphnia magna to the tested chemicals were affected in general by exposure concentration, rather than toxic characteristics of the chemicals. The duration of avoidance response (DAR) was in a power regression relationship with the toxic unit (TU), defined as the ratio of exposure concentration of the tested chemical to its LC_50–48. DAR was independent of the toxic characteristics of chemicals. However, significant behavior adjustment could be observed after exposure to deltamethrin while only step-by-step decrease in behavior strength could be observed when exposed to chlorothalonil and nitrofen. It was suggested from the observation that avoidance behaviors of Daphnia magna to exposures of chemicals with different toxic characteristics could be similar, while their specific response could be different.     

Acclimation and Deacclimation of Brown Trout (Salmo trutta) to Zinc and Copper Singly and in Combination with Cadmium or Copper

Brown trout (Salmo trutta) were chronically exposed to low and high levels of zinc (Zn) alone, copper (Cu) alone, a Zn–Cu mixture, and a Zn–cadmium (Cd) mixture all starting with eyed eggs and continuing through to the fingerling stage. Exposure to the metals and metal mixtures resulted in acclimation as measured by greater median lethal concentrations (LC₅₀) values relative to metal-naïve fry. The degree of acclimation was similar between the low and high exposures except for Cu, where acclimation was observed at the high but not the low acclimation level. The increases in tolerance relative to metal-naïve controls were usually less than a factor of 2 and never exceeded a factor of 3. Acclimation exposures did not affect hatch or survival except for the high-acclimation regime of Zn plus Cu. Acclimation came at an apparent metabolic cost because growth was decreased by most acclimation exposures. Deacclimation, as evidenced by a return of LC₅₀ values to naïve levels, occurred after 2–5 weeks in clean water.     

Protective Effects of Calcium Pre-Exposure Against Waterborne Cadmium Toxicity in Synechogobius hasta

The present study was performed to evaluate the effects of calcium (Ca) pre-exposure and then waterborne cadmium (Cd) exposure on metal element accumulation, enzymatic activities, histology, and ultrastructure in Synechogobius hasta and test the hypothesis that Ca could protect against Cd-induced toxicity in the fish species. Three hundred sixty fish [initial mean weight 25.5 ± 0.1 g (mean ± SEM)] were stocked in 18 circular fiberglass tanks (water volume: 300 l), 9 of which were pre-exposed to Ca at a rate of 400 mg Ca/l for 9 days and then exposed to concentrations of 0, 79.3, and 158.6 μg Cd/l for 9 days. Another 9 tanks were cultured in natural seawater (no extra Ca addition) for 9 days and then exposed to concentrations of 0, 79.3, and 158.6 μg Cd/l for 9 days. Both Ca pre-exposure and then waterborne Cd exposure influenced the accumulation of metal elements [cadmium (Cd), copper, zinc, and iron] in several tissues (muscle, gill, liver, spleen, and intestine), changed hepatic intermediary metabolism, and induced histological and ultrastructural alterations in tissues. In general, Ca pre-exposure seemed to mitigate the severity of Cd-induced mortality and histopathological injuries indicating that Ca pre-exposure had the capacity to decrease Cd toxicity in S. hasta.     

Bioaccumulation and Depuration Pattern of Copper in Different Tissues of Mystus vittatus, Related to Various Size Groups

The bioaccumulation pattern of copper (Cu) in gill, liver, kidney, and muscle of different sizes (fingerlings and adult age) of healthy Mystus vittatus when exposed to their respective sublethal concentrations of Cu-water, containing one-third 96-hr LC₅₀ level (6.20 and 15.95 mg L⁻¹) for short-term (120 hr) and one-eighth 96-hr LC₅₀ level (2.33 and 5.98 mg L⁻¹) for long-term experimentation, respectively, has been analyzed. The Cu shows a maximum deposition (p < 0.01) in the liver (82.12 and 70.65 μg/g) followed by gill (74.35 and 63.69 μg/g) and kidney (61.52 and 54.09 μg/g) both in fingerlings and adult fish, respectively, during 28 days of exposure. The lowest deposition of Cu is found to be 0.83 and 0.93 μg/g in fingerlings and 0.79 and 0.86 μg/g in adult muscle tissue during short-term (120 hr) and long-term (28 days) exposure periods, respectively. Comparing the accumulation of Cu on the two size groups at both exposure levels, it is obvious that the fingerlings showed higher Cu concentration in all tissues than those of adult fish. Another equally important finding is that the depuration of Cu by maintaining the bioaccumulated fish (long-term exposed group) of both size groups in quality dechlorinated ground water reveals that there is a significant (p < 0.05) reduction in Cu concentration in different tissues as the day passes. A comparison of the performance of the two size groups in respect of depuration clearly indicates that the fingerlings have taken 24–43 days (gill-kidney), whereas in mature fish it is 21–39 days (gill-kidney) to reach the level of control fish. Among the various tissues in both size groups, gill took the minimum number of days for complete recovery, whereas the muscle tissue did not significantly eliminate Cu even after 30 days of depuration. These data constitute a reference for future studies on the evolution of Cu accumulation and elimination tendency in relation to different size groups of fish in the ecotoxicological testing scheme for hazard assessment.     

Effects of Metal (Ag,Cd, Cr,Cu, Zn) Exposures on Some Enzymatic and Non-Enzymatic Indicators in the Liver of <Emphasis Type="Italic">Oreochromis niloticus</Emphasis>

Freshwater fish Oreochromis niloticus exposed to 0.05 μg/mL of Cu, Cd, Zn, Ag and Cr for up to 30 days. Only Ag, which exceeded environmentally realistic concentrations by a factor of >100 caused fish mortality within this period. Metals increased aspartate transaminase (AST) activity, while they decreased alanine transaminase (ALT) activity, except Cr exposure. Concentrations of free –SH group decreased whereas protein concentrations did not alter following metal exposures. Detectable metal accumulation occurred in the liver of Cd, Cu and Zn exposed fish. This study emphasized that both enzymatic and non-enzymatic mechanisms may be useful in understanding the degree of metal toxicity in fish liver.     

Monitoring the sensitivity of the oligochaete Tubifex tubifex in laboratory cultures using three toxicants

Acute toxicity tests were conducted to assess the sensitivity of laboratory cultured Tubifex tubifex (Annelida, Clitellata), as an intralaboratory quality assurance requirement for the test organisms used in sediment chronic bioassays. Worms were exposed to cadmium, copper, and chromium in water-only 96-h tests, in single metal exposure, over a three-year period. The lethal concentration for the x% of the exposed population (LC_x), the No-Observable-Effect Concentration (NOEC) and the Lowest-Observable-Effect Concentration (LOEC) were estimated. Based on LC₅₀ values, the rank of toxicity was Cu⁺²>Cd⁺²>Cr⁺⁶. Sensitivity remained relatively constant during the research period and was comparable with the sensitivity of the same culture stock examined more than 10 years ago. This observed consistency in sensitivity indicates that comparisons between different sediment chronic bioassays conducted during the study period, using T. tubifex worms from the same culture stock, was appropriate. It is necessary to control both worm biomass and age for the acute test in order to standardize the test-organism conditions in intralaboratory quality assurance programs.     

Effect of Yerbimat Herbicide on Lipid Peroxidation,Catalase Activity,and Histological Damage in Gills and Liver of the Freshwater Fish <Emphasis Type="Italic">Goodea Atripinnis</Emphasis>

The use of herbicides for agricultural and aquatic weed control has increased worldwide. These substances are potentially toxic pollutants because they induce the production of reactive oxygen species for biological systems and exert oxidative stress in nontarget organisms living in the treated aquatic systems. Recent evidence suggests differences in the toxicity of glyphosate in the form of an active ingredient compared to the toxicity of glyphosate in combination with surfactants, such as those found in commercial formulations. In Mexico, one of the most widely used glyphosate-based herbicides is Yerbimat, which has agricultural as well as aquatic weed control applications. However, there are no aquatic toxicity data, particularly regarding native fish. Therefore, we determined the acute toxicity of commercial-formulation Yerbimat in a static bioassay at 96 h (LC₅₀). We also determined its toxicity at 96 h in sublethal concentrations to assess the lipid peroxidation levels (LPX), catalase activity, hepatic glycogen content, and histological damage in the liver and gills of the fish Goodea atripinnis associated with chronic exposure (75 days). The LC₅₀ was 38.95 ± 0.33 mg/L. The results of the short-term exposure study indicate that Yerbimat can potentially induce oxidative stress in G. atripinnis, because LPX was increased in the gills and liver. Catalase activity was reduced in the gills but increased in the liver, whereas hepatic glycogen was depleted. Chronic exposure was associated with histopathological damage in the gills and liver, some of which was irreversible. Yerbimat represents a potential risk for aquatic biota; therefore, we recommend that its application be carefully considered.     

Using the critical body residue approach to determine the acute toxicity of cadmium at varying levels of water hardness and dissolved organic carbon concentrations

The linkage between acute adverse effects of cadmium and internal cadmium levels were investigated for the oligochaete worm Lumbriculus variegatus in water at varying degrees of hardness and two different dissolved organic carbon (DOC) concentrations. The LC₅₀s for the effect of cadmium on the survival of the worms greatly differed depending on water hardness and DOC. We found less variability in internal metal toxicity metrics (lethal residue; LR₅₀s) than in external toxicity metrics (lethal concentration; LC₅₀s): LC₅₀s varied from 2.4 to 66.1 μmol/L, while LR₅₀s varied only from 226 to 413 μmol/kg wet weight. The cadmium body burden appeared to be independent of exposure conditions. From our experimental data, a critical cadmium body residue (324±78 μmol/kg wet weight) associated with 50% lethality was derived. The protective role of DOC and water hardness against cadmium toxicity was evident.     

Stress responses and changes in protein metabolism in carp Cyprinus carpio during cadmium exposure

Stress responses and changes in protein metabolism were studied in common carp Cyprinus carpio exposed to 0, 0.8, 4, and 20 microM cadmium (Cd) over a 29-day period. Blood and other tissue samples were taken after 4 and 29 days of exposure. The highest Cd concentration proved to be lethal to the fish, resulting in 100% mortality after 21 days of exposure. Cd accumulated in the tissues in the following order: kidney>liver>gills. Blood hematocrit, blood hemoglobin, plasma glucose, plasma lactate, and tissue total protein contents were not significantly altered. The concentrations of Cd and zinc (Zn) binding metallothioneins ((Cd, Zn)-MTs) were in the following order=liver>kidney>gills. An increase in (Cd, Zn)-MTs was observed at all exposure concentrations at days 4 and 29 in kidney and at Day 29 in gills. No significant changes in (Cd, Zn)-MT contents were found in liver. The concentrations of free amino acids and the activities of proteases were increased at Day 4 in gills, liver, and kidney of carp exposed to 4 and 20 microM Cd, and in gills and kidney at Day 29 in carp exposed to 4 microM Cd. The observed increases in the activities of aspartate aminotransferase and alanine aminotransferase suggest that the observed proteolysis is intended to increase the role of proteins in the energy production during Cd stress. However, this increased activity of both aminotransferases was not found in gills during exposure to the lethal Cd concentration, indicating that Cd may also cause an inhibitory effect on the activity of these enzymes above a certain level.     

Evaluation of Fish Health Status and Histopathology in Gills and Liver Due to Metal Contaminated Sediments Exposure

Health status of freshwater fish, Cirrhina mrigala was studied by qualitative and quantitative histopathological analysis, alterations in frequency/prevalence percentages (%) and histological alteration indices (HAI) in response to metal contaminated sediments of the River Ravi aquatic ecosystem. Histo-structures of gill and liver samples of fish were analyzed and comparison between the degree of damage of the alterations in fish organs was performed after exposure to metal contaminated sediments for 7, 14 and 28 days under semi-static water renewal bioassays. Histopathological studies revealed marked histological alterations in the gills and liver of exposed fish as compared to normal tissue structure observed in control fish. The frequency and prevalence percentages observed in 28-day exposed fish were significantly higher as compared to 7- and 14-day exposed fish. The order of frequency and prevalence percentage for gills and liver of exposed fish was as: 28-day?>?14-day?>?7-day. The highest prevalence percentages recorded were 83 and 80% as focal area of necrosis in gill and liver, respectively, after 28-day exposure. The lowest prevalence percentage observed in 7-day exposed Cirrhina mrigala was dilation of sinusoids (17%).     

Toxicity of Triphenyltin Hydroxide to Fish

Triphenyltin (TPhT) is used worldwide in pesticide formulas for agriculture. Toxic effects of this compound to aquatic life have been reported; however, the biochemical response of fish exposed to different concentrations of TPhT hydroxide (TPhTH) was investigated for the first time in this study. The lethal concentration (LC₅₀) of TPhTH to silver catfish, Rhamdia quelen, was calculated from an acute-exposure experiment (96 h). In addition, acethylcholinesterase (AChE) activity in brain and muscle—as well as glucose, glycogen, lactate, total protein, ammonia, and free amino acids in liver and muscle—were evaluated in a chronic-exposure experiment (15-day exposure). Speciation analysis of tin (Sn) was performed in fish tissues at the end of both experiments using gas chromatography coupled to a pulsed-flame photometric detector (GC-PFPD). Concentrations of TPhT, diphenyltin, and monophenyltin (reported as Sn) were lower than limits of quantification (10σ criteria). Waterborne TPhTH concentration used through the experiment was also evaluated by GC-PFPD, and no degradation of this species was observed. The LC₅₀ value for silver catfish juveniles was 9.73 μg L^?1 (as Sn). Decreased brain and muscle AChE activities were observed in fish exposed to TPhTH in relation to unexposed fish (control). Liver glycogen and lactate levels were significantly higher in fish kept at the highest waterborne TPhTH concentration compared with the control. Liver and muscle glucose levels of fish exposed to all TPhTH concentrations were significantly lower than those of control fish. Silver catfish exposed to all TPhTH concentrations showed lower total protein values and higher total free amino acids levels in liver and muscle compared with controls. Total ammonia levels in liver and muscle were significantly higher for the highest TPhTH concentration compared with controls. In conclusion, TPhTH caused metabolic alterations in silver catfish juveniles, and the analyzed parameters can also be used as bioindicators for TPhTH contamination.