Acute effects of nitrite on ion regulation in two neotropical fish species

Weathered polyethylene microplastics induced immunomodulation in zebrafish

Microplastics are pollutants of emerging concern and the aquatic biota consumes microplastics (MPs), which has a range of toxicological and environmental effects on aquatic organisms that are not the intended targets. The current study looked into how weathered polyethylene (wPE) MPs affected Danio albolineatus immunological and haematological markers. In this experiment, fish of both sexes were placed in control and exposure groups, and they were exposed for 40 d at the sublethal level (1 μg L-1) of fragmented wPE, which contained 1074 ± 52 MPs per litre. Similarly, fish exposed to wPE MPs showed significant modifications in lysozyme, antimicrobial, and antiprotease activity, as well as differential counts. Results of the present study show that the male fish were more susceptible than female fish after 40 d of chronic exposure. Further studies are needed to ascertain how the innate and humoral immune systems of the fish respond to MPs exposure.

Impact of sublethal phenol in freshwater fish Labeo rohita on biochemical and haematological parameters

Phenol, an aromatic chemical commonly found in domestic and industrial effluents, upon its introduction into aquatic ecosystems adversely affects the indigenous biota, the invertebrates and the vertebrates. With the increased demand for agrochemicals, a large amount of phenol is released directly into the environment as a byproduct. Phenol and its derivatives tend to persist in the environment for longer periods which in turn poses a threat to both humans and the aquatic ecosystem. In our current study, the response of Labeo rohita to sublethal concentrations of phenol was observed and the results did show a regular decrease in biochemical constituents of the targeted organs. Exposure of Labeo rohita to sublethal concentration of phenol (22.32 mg/L) for an epoch of 7, 21 and 28 days shows a decline in lipid, protein, carbohydrate content and phosphatase activity in target organs such as the gills, muscle, intestine, liver and kidney of the fish. The present study also aims to investigate the toxic effects of phenol with special reference to the haematological parameters of Labeo rohita. At the end of the exposure period, the blood of the fish was collected by cutting the caudal peduncle with a surgical scalpel. And it was observed that the red blood corpuscle count (RBC), white blood corpuscle (WBC), haemoglobin count (Hb), packed cell volume (PCV), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH) and mean corpuscular haemoglobin concentration (MCHC) values showed a decline after exposure to phenol for 7 days, while white blood corpuscle (WBC) shows an increased count. At 21 days and 28 days, all the haematological parameters showed a significant decrease.

Effect of low-dose Piscirickettsia salmonis infection on haematological-biochemical blood parameters in Atlantic salmon (Salmo salar)

Piscirickettsia salmonis is the etiological agent of Piscirickettsiosis, a severe disease that affects Atlantic salmon (Salmo salar) farmed in Chile and many other areas (Norway, Scotland, Ireland, Canada and the USA). This study investigated the effects of low-dose P. salmonis infection (1 × 10²  CFU/ml) on Atlantic salmon. In this study, we challenged fish with an isolated representative of the EM-90 genogroup via intraperitoneal injection for 42 days. Infected fish displayed decreased haematocrit and haemoglobin levels at day 13 post-infection, indicating erythropenia, haemolysis and haemodilution. Conversely, their white blood cell counts increased on days 13 and 21 post-infection. Additionally, their iron levels decreased from day 2 post-infection, indicating iron deficiency and an inability to retrieve stored iron before infection. Their magnesium levels also decreased at day 28 post-infection, possibly due to osmoregulatory problems. Also, we observed an increase in lactate dehydrogenase activity on days 5, 21, and 28 post-infection, suggesting early symptoms of hepatotoxicity. Later analyses determined a decrease in plasma glucose levels from day 2 post-infection. This may be attributed to the hypoxic conditions caused by P. salmonis, leading to an excess utilization of stored carbohydrates. Our results suggest that the blood parameters we studied are useful for monitoring the physiological status of Atlantic salmon infected with P. salmonis.

Intestinal changes associated with nitrite exposure in Bufo gargarizans larvae: Histological damage, immune response, and microbiota dysbiosis

Nitrite is a ubiquitous toxic compound in aquatic ecosystems and has negative effects on aquatic organisms. The intestine and the trillions of microbes that inhabit it, play an integral role in maintaining digestive and immune functions. However, the effects of nitrite on intestinal health and microflora have been poorly investigated. Therefore, the present study evaluated the response of intestinal histology, immunity, digestive enzyme activities and microbiota to nitrite exposure in Bufo gargarizans tadpoles. The results showed that nitrite caused damage to the intestine and impaired digestive performance. Significant changes in the transcriptional profiles of genes involved in oxidative stress (sod, gpx and hsp), inflammation, and immunity (socs3, il-27, il-1β and il-17d) were observed in the NO₂-N treatment groups. In addition, exposure to nitrite induced alterations of intestinal microbial diversity, structure and composition, suggesting that nitrite may lead to intestinal microbiota dysbiosis. It is noteworthy that probiotics (e.g., Bacteroidetes and Fusobacteria) were decreased after exposure to nitrite, whereas potentially opportunistic pathogens such as Proteobacteria and Enterobacteriaceae were elevated. Functional prediction and correlation analysis suggested that the above changes may interfere with metabolic function and trigger various diseases. Taken together, we concluded that nitrite exposure induced intestinal microbial dysbiosis, which may lead to immune dysfunction and metabolic disorder, and ultimately to histological damages in B. gargarizans. Further, this study will provide a scientific basis for further understanding the risk of nitrite pollution on the intestinal health of amphibians.

Effects of nitrite exposure on metamorphosis and skeletal development of Bufo gargarizans

Nitrite, as a part of nitrogen cycle, is one of the most common toxic compounds in aquatic ecosystems. Since skeletal development is an essential process during amphibian metamorphosis, exposure of larval amphibians to nitrite might disrupt skeletal development. To evaluate whether nitrite affects skeletal development of amphibian larvae, Bufo gargarizans larvae at Gs26 were exposed to 10, 100, 500 and 1000 μg/L nitrite-nitrogen (NO₂-N) in the present study. The metamorphosis rate, body weight, body length, forelimb length and hindlimb length of B. gargarizans exposed to NO₂-N were decreased. The microscopic structures of thyroid gland were altered under NO₂-N exposure at Gs42. The skeletal lengths of the humerus, femur and fibulare of tadpole at Gs42 were significantly reduced under 100, 500 and 1000 μg/L NO₂-N treatment groups, and the lengths of humerus, tibia-fibula and tibiale of tadpole at Gs46 were significantly reduced under 1000 μg/L NO₂-N treatment groups. In addition, the expression levels of thyroid hormone (TH) and endochondral ossification-related genes of tadpoles at Gs42 and Gs46 were tested by qRT-PCR. Overall, NO₂-N exposure could affect the expressions of these genes and then may influence the activity and function of thyroid gland, further disturbing the amphibian metamorphosis and skeletal development of amphibian larvae.

Nitrite Stress Induces Oxidative Stress and Leads to Muscle Quality Decreased in Wuchang Bream (Megalobrama amblycephala Yih) Juveniles

To determine the effects of nitrite exposure on muscle quality and physiological functions in Wuchang bream (Megalobrama amblycephala), we exposed M. amblycephala juveniles to acute nitrite (0, 1, 5, 10, 20 mg/L), and the muscle and blood samples were measured at 12, 24, 48, and 96 h. The results showed that when exposed to nitrite for 12 h, the concentrations of blood glucose, cortisol, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) in the 20 mg/L experimental group had the maximum value. The activity of lactate dehydrogenase (LDH) increased significantly in a dose-dependently manner and peaked at 96 h in the 20 mg/L group. During 96 h of exposure to nitrite, the total antioxidant capacity (T-AOC) and catalase (CAT) activity in the liver of the 20 mg/L experimental group were significantly higher than those of the control group, while the concentration of muscle glycogen showed a downtrend. At 12 h and 96 h, the hardness of the four experimental groups were significantly higher than that of the control group. Our research shows that acute sodium nitrite exposure will not only cause oxidative stress and decreased muscle quality in M. amblycephala juveniles but also will be accompanied by changes in serum biochemical index, liver antioxidant capacity, muscle physiological characteristics, and muscle physical characteristics. Preliminary speculation may be that acute nitrite exposure may cause M. amblycephala juveniles to choose to reduce muscle quality and activate antioxidant systems.

Ivermectin: A multilevel approach to evaluate effects in Prochilodus lineatus (Valenciennes, 1836) (Characiformes, Prochilodontidae), an inland fishery species

Ivermectin (IVM) is one of the most widely used antiparasitics worldwide. It is a potent and effective drug for treatment and prevention of internal and external parasitic infections of livestock and humans. IVM is excreted unchanged in manure of treated animals. Thus, residues of IVM may reach aquatic systems, affecting non-target organisms such as fish. Although the presence of IVM in aquatic environments has been reported, a multilevel approach (from cellular to behavioral responses) is necessary to determine the health of exposed organisms and the environmental risks associated. The aim of the present study was to investigate the response of the Neotropical fish Prochilodus lineatus, one of the main target species of South American freshwater fisheries, exposed to environmental concentrations of IVM: low (0.5 μg L^-1) and high (1.5 μg L^-1). Behavioral responses were assessed in juvenile fish and included water column use, routine swimming, total distance travelled, total activity time and Maximum swimming speed achieved during the escape response. Biochemical/oxidative stress responses assessed included brain acetylcholinesterase (AChE), catalase (CAT) and glutathione S-transferase (GST) activities; total antioxidant competence against peroxyl radicals (ACAP) and lipid oxidative damage (TBARs). Hematological biomarker responses included blood glucose levels, hematocrit, hemoglobin concentration, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, and mean corpuscular volume. Condition factor and hepatosomatic index were also calculated. The lowest IVM concentration caused a significant decrease in GST activity and maximum swimming speed during the escape response. Multivariate analysis with biochemical/stress and behavioral data revealed overall effects of IVM treatments. This multilevel analysis shows detrimental effects related to swimming behavior and predator avoidance which could affect population size and size-structure of P. lineatus. To our knowledge this is the first attempt to assess the effects of IVM on Neotropical fishes using an integrative approach based on biomarkers from different levels of biological organization.

A multibiomarker approach in the caged neotropical fish to assess the environment health in a river of central Brazilian Cerrado

Water safety is a world-wide concern and several efforts have been made in order to ensure the conservation of aquatic ecosystems. Water quality monitoring must be performed with an integrated approach using biomonitor organisms allied to water parameters. Nonetheless, very few studies have focused on biomarker responses in neotropical fish, especially in the freshwater ecosystem of Brazilian Cerrado savanna. In present study, the active biomonitoring of the João Leite river (central Brazilian Cerrado river) was performed through the evaluation of biomarker responses in caged Astyanax lacustris in combination with land use classification and analysis of water parameters. Caged fish were exposed for seven days at four sites along the river and two control groups were kept in a tank under controlled conditions. Results showed that pasture was the predominant land use in the João Leite river basin (54.07%), followed by natural vegetation (34.92%) and other kind of land use (11.01%). Water analyses showed metal concentrations (Mn and Fe) above the maximum allowed by Brazilian regulation, with particularly higher concentrations at Site 2 (near to pasture area). Biomarker responses did not show significant differences for somatic and mutagenic biomarkers between sites. However, the comet assay showed high DNA damage at Sites 2 and 3, indicating genotoxic effects in caged fish at pasture areas. Histopathological analysis showed highest frequency of leukocyte infiltration in liver of fish from Site 2, confirming the ecotoxic effects on A. lacustris in streams impacted by grazing activities. DNA damage and leukocyte infiltration in fish hepatic tissues were sensitive biomarkers in the neotropical fish A. lacustris to assess the environment health of the Cerrado river. These results showed the importance of using a multibiomarker approach in environmental risk assessment, especially in areas more at risk from anthropogenic pollution.

Effect of nitrite exposure on haematological status, oxidative stress, immune response and apoptosis in yellow catfish (Pelteobagrus fulvidraco)

Nitrite can cause fishes poisoning. This study evaluated the effects of nitrite exposure on haematological status, ion concentration, antioxidant enzyme activity, immune response, cytokine release and apoptosis in yellow catfish. In this study, yellow catfish were exposed to three levels of nitrite (0, 3.00 and 30.00 mg L^-1) for 96 h. The results showed that nitrite poisoning could lead to blood deterioration (red blood cell and hemoglobin reduced; white blood cell and methemoglobin elevated), ion imbalance (Na⁺ and Cl^- declined; K⁺ elevated), oxidative stress (total antioxidant capacity, superoxide dismutase, catalase and glutathione peroxidase activities declined; malondialdehyde accumulation), immunosuppression (lysozyme activity, 50% hemolytic complement, immunoglobulin M, respiratory burst and phagocytic index declined) and cytokines release (TNF, IL 1 and IL 8 elevated). In addition, nitrite poisoning could induce up-regulation of antioxidant enzymes (Cu/Zn-SOD, Mn-SOD, CAT and GPx), cytokines (TNF, IL 1 and IL 8) and apoptosis (P53, Bax, Cytochrome c, Caspase 3, Caspase 9, ERK and JNK) genes transcription. This study suggesting that the nitrite exposure triggers blood deterioration, disrupts the ionic homeostasis, induces oxidative stress, immunosuppression, inflammation and apoptosis in yellow catfish.

A method to analyze the sensitivity ranking of various abiotic factors to acoustic densities of fishery resources in the surface mixed layer and bottom cold water layer of the coastal area of low latitude: a case study in the northern South China Sea

This is an exploratory analysis combining artificial intelligence algorithms, fishery acoustics technology, and a variety of abiotic factors in low-latitude coastal waters. This approach can be used to analyze the sensitivity level between the acoustic density of fishery resources and various abiotic factors in the surface mixed layer (the water layer above the constant thermocline) and the bottom cold water layer (the water layer below the constant thermocline). The fishery acoustic technology is used to obtain the acoustic density of fishery resources in each water layer, which is characterized by Nautical Area Scattering Coefficient values (NASC), and the artificial intelligence algorithm is used to rank the sensitivity of various abiotic factors and NASC values of two water layers, and the grades are classified according to the cumulative contribution percentage. We found that stratified or multidimensional analysis of the sensitivity of abiotic factors is necessary. One factor could have different levels of sensitivity in different water layers, such as temperature, nitrite, water depth, and salinity. Besides, eXtreme Gradient Boosting and random forests models performed better than the linear regression model, with 0.2 to 0.4 greater R² value. The performance of the models had smaller fluctuations with a larger sample size.

Short-term mercury exposure in tilapia (Oreochromis niloticus) at different salinities: impact on serum osmoregulation, hematological parameters, and Na+/K+-ATPase level

The objectives of this study were to analyze and compare the effects of mercury (Hg) exposure on osmoregulation and hematological responses in East Java strain tilapia (Oreochromis niloticus). Fish were exposed to 0, 0.1, and 1 mg L-1 Hg at 0, 5, 10, and 15 g L-1 salinities, and serum osmolality (SO), ion level, hematological parameters, and sodium (Na+)/potassium (K+)-ATPase (NKA) levels in the gills and kidney were assessed after 96 h of exposure. SO significantly increased in fish exposed to Hg at 15 g L-1 salinity compared with those exposed at 0, 5, 10, and 15 g L-1 salinities, but SO did not significantly increase in fish exposed to Hg at 5 and 10 g L-1 salinities compared with those exposed at 0 g L-1 salinity. At 15 g L-1 salinity, the Na+ level was significantly different from that at 0, 5, and 10 g L-1 salinities. The chloride ion level significantly increased only at 15 g L-1 salinity. Furthermore, the K+ level was significantly different at 10 and 15 g L-1 salinities from that at 0 and 5 g L-1 salinities. Hematocrit and hemoglobin levels and red blood cell and white blood cell (WBC) counts were not significantly different among all salinities. At 15 g L-1 salinity, the NKA level in the gills was significantly different from that at 0 g L-1 salinity, but in the kidney, there was no difference among all salinities. These data provide useful information for future reference and aquaculture practices to reduce Hg effects on tilapia. In conclusion, higher salinity reduced the effect of Hg on the K+ level and WBC count in tilapia.

Efeitos tóxicos dos sedimentos do estuário do rio Capibaribe em embriões de zebrafish (Danio rerio)

RESUMO O presente estudo utilizou embriões de Danio rerio expostos aos elutriatos dos sedimentos estuarinos do rio Capibaribe, dos períodos chuvoso e seco, e analisou os efeitos letais, teratogênicos, bem como a frequência cardíaca. Os testes de toxicidade com os embriões seguiram as diretrizes da OECD 236. Mediante os resultados obtidos, a frequência cardíaca e a teratogenicidade foram os efeitos mais observados nos animais quando submetidos às amostras. Entre os efeitos teratogênicos, o retardo geral no desenvolvimento dos embriões foi o mais frequente durante as análises. Tais efeitos tóxicos se modificaram entre os pontos e entre os períodos de coleta. Essa variação de toxicidade pode estar relacionada à diversidade de atividades realizadas no entorno desse estuário, a influência do regime de chuvas, marés e correntes, indicando que a análise dos efeitos subletais e da teratogenicidade em embriões de D. rerio constitui bom parâmetro para avaliações de toxicidade de amostras ambientais.

Effect of acute exposure to nitrite on physiological parameters, oxidative stress, and apoptosis in Takifugu rubripes

In the present study, we evaluated the effects of nitrite exposure on hematological parameters, oxidative stress, and apoptosis in juvenile Takifugu rubripes. The fish were exposed to nitrite (0, 0.5, 1, 3, and 6 mM) for up to 96 h. In the high nitrite concentration groups (i.e., 3 and 6 mM), the concentrations of methemoglobin (MetHb), cortisol, glucose, heat shock protein (Hsp)-70, Hsp-90, and potassium (K⁺) were significantly elevated. Whereas, the concentrations of hemoglobin (Hb), triglyceride (TG), total cholesterol (TC), and sodium (Na⁺) and chloride (Cl^-) ions were significantly decreased. Compared with those of the control groups, the concentrations of the antioxidant enzymes, namely, superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and glutathione peroxidase (GPx), in the gills were considerably elevated at 12 and 24 h after exposure to nitrite (1, 3, and 6 mM), but reduced at 48 and 96 h. The increase in the antioxidant enzymes may contribute to the elimination of reactive oxygen species (ROS) induced by nitrite during early nitrite exposure, when the antioxidant system is not sufficiently effective to eliminate or neutralize excessive ROS. In addition, we found that nitrite exposure could alter the expression patterns of some key apoptosis-related genes (Caspase-3, Caspase-8, Caspase-9, p53, Bax, and Bcl-2). This indicated that the caspase-dependent apoptotic pathway and p53-Bax-Bcl-2 pathway might be involved in apoptosis induced by nitrite exposure. Furthermore, our study provides insights into how acute nitrite exposure affects the physiological responses and potential molecular mechanism of apoptosis in marine fish. The results can help elucidate the mechanisms involved in nitrite-induced aquatic toxicology in marine fish.

Impact of nitrite exposure on plasma biochemical parameters and immune-related responses in Takifugu rubripes

Nitrite is a major environmental pollutant in aquatic environments that negatively affects aquatic species. In this study, we investigated the impact of nitrite exposure on plasma biochemical parameters and immune responses in Takifugu rubripes. Fish were exposed to various concentrations of nitrite (0, 0.5, 1, 3, and 6 mM) for 96 h. After 0, 12, 24, 48, and 96 h of exposure, fish blood samples were collected to assay the levels of total protein (TP), albumin (Alb), glutamic-oxaloacetic transaminase (GOT), glutamic-pyruvic transaminase (ALT), complement C3 (C3), complement C4 (C4), immunoglobulin (IgM), and lysozyme activity (LZM). The gills were sampled to analyze the mRNA levels of heat shock protein 70 (hsp70), heat shock protein 90 (hsp90), tumor necrosis factor α (tnf-α), B-cell activating factor (baff), interleukin-6 (il-6), and interleukin-12 (il-12). Levels of GOT, ALT, C3, and C4 were significantly enhanced in the high nitrite concentration group (3 and 6 mM), whereas those of TP, Alb, LZM, and IgM decreased significantly with the same treatments. Nitrite significantly upregulated hsp70, hsp90, tnf-α, il-6, il-12, and baff mRNA levels after 96 h of exposure. These results indicated that nitrite exposure altered the blood physiological status and immune system response, resulting in dysfunction and immunotoxicity in T. rubripes. Furthermore, our results reveal the possible mechanism of aquatic-nitrite-induced toxicity in fish.

Exposure to nitrite alters thyroid hormone levels and morphology in Takifugu rubripes

Nitrite (NO^2-) can act as a toxic nitrogenous compound with the potential to disrupt endocrine systems in fish. The aim of the present study was to investigate the effects of nitrite on the thyroid endocrine system of Takifugu rubripes. Fish were exposed to 0, 0.5, 1, 3, and 6 mM nitrite concentrations. Blood was collected to assay the concentrations of thyroid-stimulating hormone (TSH), thyroxine (T₄), triiodothyronine (T₃), free thyroxine (FT₄), free triiodothyronine (FT₃), and 3,3,5'-triiodothyronine (rT₃), as well as the activity of iodothyronine deiodinases (Dio1, Dio2, and Dio3,) after 0, 12, 24, 48, and 96 h of exposure to nitrite. The first branchial arch to the third branchial arch of T. rubripes were sampled and fixed, and thyroid morphology was observed. The results showed that exposure to nitrite significantly increased the concentrations of TSH, T₃, FT₃, and reduced the concentrations of T₄, FT₄, and rT₃. The activity of Dio1 and Dio2 increased significantly, whereas Dio3 activity decreased significantly. Additionally, thyroid follicles degenerated and became blurred and most colloid material disappeared 96 h after exposure to high nitrite concentrations. Based on these results, high nitrite concentration exposure can disturb thyroid hormone homeostasis, alter thyroid follicle morphology, and result in thyroid endocrine toxicity.

Exposure time relevance of response to nitrite exposure: Insight from transcriptional responses of immune and antioxidant defense in the crayfish, Procambarus clarkii

To understand the toxic effects of nitrite exposure on crayfish, expression of genes involved in the immune system, the antioxidant defense, and the heat shock protein 70 (HSP70) was measured after 12, 24, and 48 h of different nitrite concentrations exposure in the hepatopancreas and hemocytes of Procambarus clarkii. Nitrite exposure up-regulated mRNA levels of cytoplasmic Mn superoxide dismutase (cMn-SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione-S-transferase (GST), after 24 h nitrite exposure. At 48 h, nitrite exposure decreased the mRNA levels of mitochondrial MnSOD (mMn-SOD), CAT, and GPx. High concentrations of nitrite at 48 h of exposure decreased expression of β-1,3-glucan-bingding protein in the hepatopancreas, and lysozyme expression in hemocytes. Nitrite exposure caused little effect on the heat shock protein 70 (HSP70) in hemocytes. Through overall clustering analysis, we found that 24 h of nitrite exposure caused stronger transcriptional responses. Our study indicated that the response of P. clarkii to acute nitrite exposure was exposure time-dependent. These results will help to understand the dynamic response pattern of crustaceans to nitrite pollution, and improve our understanding of the toxicological mechanisms of nitrite in crustaceans.

Waterborn Genotoxicity in Southern Brazil Using Astyanax bifasciatus (Pisces: Teleostei)

Water bodies are often negatively affected by unmediated expansion of surrounding human populations. This makes it essential to establish growth planning strategies that balance productivity and sustainability when creating a viable ecological equilibrium. This study aimed to evaluate genotoxic effects in southern Brazil, using biomarkers in the fish Astyanax bifasciatus, during summer and winter of 2016. The erythrocytic nuclear abnormalities test and the micronucleus test as well as the blood and liver comet assay were used to determine genetic biomarker damage. Four locations and a control point (CP) were sampled in this study. The results demonstrated genotoxicity at all sample locations in the river as compared to the CP in all tests. This is concerning as this water source is the only supply for human populations adjacent and further flows into the greater Iguaçu river basin.

The Effect of Sodium Nitrite Exposure on Physiological Response of Starved Far Eastern Catfish, Silurus asotus

The experiment was conducted for 210 days to determine the effect of feeding, and starvation, and exposure to sodium nitrite (NaNO₂) on the survival, physiological changes, hematological parameter, and stress response of Far Eastern catfish, Silurus asotus. The survival of the starved group was lower than that of the fed group during the experiment. Starvation resulted in retardation of growth, which provides an example of fish that failed to continue to grow and remain in a good condition. Blood analyses (cortisol and glucose) showed significant differences of stress response between the fed and starved groups exposed to NaNO₂ at the conclusion of the experiment (p<0.05). These results suggest that all nutritional parameters used for starvation and feeding with NaNO₂ stress in this experiment appear to be a useful index of nutritional status in Far Eastern catfish.

Biological responses of Neotropical freshwater fish Lophiosilurus alexandri exposed to ammonia and nitrite

This study aimed to elucidate the responses of the Neotropical fish Lophiosilurus alexandri exposed to ammonia and nitrite, following a period of recovering. Acute toxicity tests lasted 96h, subchronic toxicity tests lasted eight days and the detoxification trial lasted four days. Groups of 12 juveniles were maintained in 90-L tanks and treated with increasing concentrations of ammonia and nitrite, except during the recovery test. All treatments were performed with two replicates. The median lethal concentrations (LC₅₀) of 24, 48, 72 and 96h were estimated at 30.12; 24.35; 19.24 and 18.68mg·L^-1 TA-N; 5.37; 4.57; 3.75 and 3.66mg·L^-1 NH₃-N and 20.37; 7.78; 7.09 and 5.86mg·L^-1 NO₂^--N, respectively. The NO₂^- caused significant decrease in hematocrit and increase in the urea levels during short-term exposure, with recovery of homeostasis after the subchronic and detox period. Acute exposure to ammonia increased the enzyme profile of transaminases, glucose and urea. Urea concentration remained high in the subchronic and detox tests. Histopathologies were observed in animals exposed to ammonia in both toxicity tests. It was highlighted detachment of epithelium, hyperemia and necrosis in the gills. Exposure to NO₂^- caused epithelium detachment and aneurysm. Vacuolization and swelling of hepatocytes were the most common injury for both nitrogenous compounds. We concluded that the L. alexandri has moderate tolerance to ammonia and nitrite. The recovery period revealed remedial response to ammonia and nitrite exposure.

Mitochondria-rich cells changes induced by nitrite exposure in tambaqui (Colossoma macropomum Cuvier, 1818)

The gill mitochondria-rich cells of the juvenile Amazonian fish Colossoma macropomum were analyzed using light and scanning and transmission electron microscopy after 96 h exposure to 0.04 and 0.2 mM nitrite. Although the number of mitochondria-rich cells decreased significantly in the lamellar epithelium, no decrease was found in the interlamellar region of the gill filament. Nitrite exposure caused significant reduction on the apical surface area of individual mitochondria-rich cells (p < 0.05), with a resulting reduction of the fractional area of these cells in both the lamellar and filament epithelium. Swelling of endoplasmic reticulum cisternae, nuclear envelope and mitochondria were the main changes found in the mitochondria-rich cells. Cristae lysis and matrix vacuolization characterized the mitochondrial changes. The overall ultrastructural changes indicated cellular functional disruption caused by exposure to nitrite. The changes observed in the gill indicate that the cellular structures involved in the process of energy production become severely damaged by exposure to nitrite indicating irreversible damage conducting to cell death.

Haematological and immune upshots in Clarias batrachus exposed to dimethoate and defying response of dietary ascorbic acid

Dimethoate (DM) is an organophosphate insecticide used worldwide in agriculture, household practices. It has resulted in a series of environmental and toxicological impacts on non-target aquatic organisms. The present study investigated the potential ameliorative effects of dietary ascorbic acid (AA) against dimethoate toxicity in the haematological and immune parameters in Clarias batrachus. The experiment included group A (basal diet), group B (basal diet with 1.245 mg L^-1 DM) and group C (200 mg kg^-1 AA with 1.245 mg L^-1 DM) were fed for 8 weeks. Samples were collected at the end of every week in each group and estimated haematological profile (red blood cell count, haemoglobin concentration, haematocrit %, albumin and globulin levels), erythrocyte indices (mean corpuscular volume, mean corpuscular haemoglobin, and mean corpuscular haemoglobin concentration), biochemical parameters (AA levels in blood and liver, total proteins, glucose, serum triglycerides, creatinine levels and glutamic oxaloacetate, glutamic pyruvate transaminase (GOT, GPT)) and immune responses (white blood cell count, serum IgM levels and activities of nitroblue tetrazolium, lysozyme and peroxidase) of the fish. Fish fed with ascorbic acid, showed red blood cell, haemoglobin, haematocrit, erythrocyte indices, albumin, globulin and serum triglycerides, creatinine, plasma total proteins, glucose levels are not differed (≤10%) from control. Likewise, ascorbic acid maintains optimal levels in activities of GOT, GPT, nitroblue tetrazolium, lysozyme and peroxidase, white blood cells and serum IgM levels. Further studies are needed to ascertain how ascorbic acid improves the innate and humoral immune system of the fish and the mechanisms involved.

Integrated biomarker response in catfish Hypostomus ancistroides by multivariate analysis in the Pirapó River, southern Brazil

Aquatic pollutants produce multiple consequences in organisms, populations, communities and ecosystems, affecting the function of organs, reproductive state, population size, species survival and even biodiversity. In order to monitor the health of aquatic organisms, biomarkers have been used as effective tools in environmental risk assessment. The aim of this study is to evaluate, through a multivariate and integrative analysis, the response of the native species Hypostomus ancistroides over a pollution gradient in the main water supply body of northwestern Paraná state (Brazil). The condition factor, micronucleus test and erythrocyte nuclear abnormalities (ENA), comet assay, measurement of the cerebral and muscular enzyme acetylcholinesterase (AChE), and histopathological analysis of liver and gill were evaluated in fishes from three sites of the Pirapó River during the dry and rainy seasons. The multivariate general result showed that the interaction between the seasons and the sites was significant: there are variations in the rates of alterations in the biological parameters, depending on the time of year researched at each site. In general, the best results were observed for the site nearest the spring, and alterations in the parameters at the intermediate and downstream sites. In sum, the results of this study showed the necessity of a multivariate analysis, evaluating several biological parameters, to obtain an integrated response to the effects of the environmental pollutants on the organisms.

Genetic and Hematologic Endpoints in Astyanax altiparanae (Characidae) After Exposure and Recovery to Water-Soluble Fraction of Gasoline (WSFG)

The sublethal effects of water-soluble fraction of gasoline (WSFG, 1.5 % v/v) were evaluated in the freshwater fish, Astynax altiparanae, after acute exposure (96 h) under a semi-static system. In addition, the recovery process was assessed in the fish following contaminant depuration. Recovery treatments were carried out with gradual depuration (GD), consisting of 7 days in the WSFG, followed by 8 days in clean water; and treatments with total depuration in clean water for 15 (DEP 15) and 30 days (DEP 30). The effects were evaluated through the piscine micronucleus test and by differential counting of organic defense cells. Acute exposure increased the frequency of neutrophils. In the GD treatment, the thrombocyte count and erythrocytic nuclear abnormalities (ENA) increased. In the DEP 15 treatment, there was a reduction of ENA; and following 30 days of depuration (i.e., DEP 30), the number of lymphocytes increased and the thrombocyte count remained high. These results indicate a long-term response to a condition of stress from WSFG.

The physiological performance and immune response of juvenile turbot (Scophthalmus maximus) to nitrite exposure

Nitrite (NO(2-)) is the most common toxic nitrogenous compound in aquatic environment. The aim of the present study was to investigate the effects of nitrite physiological performance and immune response of turbot. Fish were exposed to 0, 0.02, 0.08, 0.4 and 0.8 mM nitrite for 96 h. After 0, 24, 48 and 96 h of exposure, blood were collected to measure the levels of glutamate pyruvate transaminase (GPT), glutamate oxalate transaminase (GOT), alkaline phosphatase (ALP), total protein (TP), albumin (Alb), complement C3 (C3), complement C4 (C4), immunoglobulin M (IgM) and lysozyme (LYS); gill samples were taken to analyze mRNA levels of LYS, heat shock protein 70 (HSP 70), heat shock protein 90 (HSP 90), metallothionein (MT), toll-like receptor 3 (TLR-3), tumor necrosis factor α (TNF-α), interleukin-1β (IL-1β) and insulin-like growth factor I (IGF-I). The results showed that nitrite (0.4 and/or 0.8mM) significantly increased the levels of GPT, GOT, ALP, C3 and C4, reduced the levels of IgM and LYS, up-regulated the gene expressions of HSP 70, HSP 90, MT, TLR-3, TNF-α and IL-1β, and down-regulated the gene expressions of LYS and IGF-1 after 48 and 96 h of exposure. Based on the results, it can be concluded that high level nitrite exposure results in dysfunction of the blood physiology and immunity in turbot. Further, this study will be helpful to understand the mechanism of aquatic toxicology induced by nitrite in marine fish.

Effects of nitrite exposure on haematological parameters, oxidative stress and apoptosis in juvenile turbot (Scophthalmus maximus)

Nitrite (NO2(-)) is commonly present as contaminant in aquatic environment and toxic to aquatic organisms. In the present study, we investigated the effects of nitrite exposure on haematological parameters, oxidative stress and apoptosis in juvenile turbot (Scophthalmus maximus). Fish were exposed to various concentrations of nitrite (0, 0.02, 0.08, 0.4 and 0.8mM) for 96 h. Fish blood and gills were collected to assay haematological parameters, oxidative stress and expression of genes after 0, 24, 48 and 96 h of exposure. In blood, the data showed that the levels of methemoglobin (MetHb), triglyceride (TG), potassium (K(+)), cortisol, heat shock protein 70 (HSP70) and glucose significantly increased in treatments with higher concentrations of nitrite (0.4 and/or 0.8mM) after 48 and 96 h, while the levels of haemoglobin (Hb) and sodium (Na(+)) significantly decreased in these treatments. In gills, nitrite (0.4 and/or 0.8mM) apparently reduced the levels of superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT) and glutathione (GSH), increased the formation of malondialdehyde (MDA), up-regulated the mRNA levels of c-jun amino-terminal kinase (JUK1), p53, caspase-3, caspase-7 and caspase-9 after 48 and 96 h of exposure. The results suggested caspase-dependent and JUK signaling pathways played important roles in nitrite-induced apoptosis in fish. Further, this study provides new insights into how nitrite affects the physiological responses and apoptosis in a marine fish.

In situ assessment of a neotropical fish to evaluate pollution in a river receiving agricultural and urban wastewater

We aimed to assess the quality of a midsize river that receives agricultural and urban wastewater. Nuclear abnormalities (NA), comet assays of blood and gills, and gill histopathology were evaluated in fish Astyanax aff. paranae during the summer and winter 2011 at three sites in Paraná State, Brazil: (1) a biological reserve (Rebio-reference area); (2) an agricultural site; (3) a downstream site that accumulates agricultural and urban effluents. We found the highest effects of pollutants in fish at the downstream site during the summer. The agricultural site showed an intermediate damage rate, and fish at Rebio generally had the least damage, with the exception of NA. Despite conflicting results from the biomarkers used, we observed an increase in damage associated with the accumulation of pollutants. Pesticides are probable xenobiotics in the agricultural area. Additionally, metals and substances such as pharmaceuticals and ammonia may be present at the downstream site.

Short and long-term effects of clofibric acid and diclofenac on certain biochemical and ionoregulatory responses in an Indian major carp, Cirrhinus mrigala

Extensive use of pharmaceuticals in human and veterinary medicine and aquaculture practices pose a serious threat to aquatic organisms. In the present investigation, Cirrhinus mrigala an Indian major carp was exposed to different concentrations of clofibric acid (CA) and diclofenac (DCF) and certain biochemical and ionoregulatory responses were assessed under short and long term exposures. During short-term (96h) exposure period, plasma glucose and sodium (Na(+)) levels were increased at all concentrations (1, 10 and 100μgL(-1)) of CA and DCF treated fish. Plasma protein and chloride (Cl(-)) levels were found to be decreased at all concentrations of CA and DCF exposed fish comparatively to control groups. Meanwhile an increase in plasma potassium (K(+)) level was noted in fish exposed to CA treatments alone and in DCF treatments it was decreased. In long-term exposure (35d), plasma Na(+) and Cl(-) levels were found to be significantly increased at all concentration of CA and DCF. However, a biphasic trend was observed in plasma glucose, protein and K(+) levels. In both the treatments, a significant (P<0.01 and P<0.05) changes were observed in all parameters measured in fish exposed to different concentrations of CA and DCF. The results of the present investigation indicate that both the drugs caused significant changes in biochemical and ionoregulatory responses of fish at all concentrations. The alterations of these parameters can be useful in monitoring of pharmaceutical residues present in aquatic environment.

Effect of azadirachtin on haematological and biochemical parameters of Argulus-infested goldfish Carassius auratus (Linn. 1758)

Argulosis hampers aquaculture production and alters the host physiology and growth. Azadirachtin is recognized as a potential antiparasitic agent against Argulus sp. The present study aimed to investigate the effect of different concentration of azadirachtin solution on haematological and serum biochemical parameters of Argulus-infested goldfish Carassius auratus. Ninety Argulus-infested goldfish were randomly divided into six equal groups. Fish of group 1-5 were treated with azadirachtin solution through bath of 1, 5, 10, 15 and 20 mg L(-1) as T1, T2, T3, T4 and T5, respectively, and group 6 was exposed to 2% DMSO solution without azadirachtin and considered as negative control T0(-). Along with six treatment groups, a positive control T0(+) of healthy goldfish free from Argulus infestation was also maintained. Parasitic mortality was evaluated after 3 days of consecutive bath treatment. After 7 days of post-treatment, the blood and serum were drawn from each of the treatment groups and haematological and serum biochemical parameters were evaluated. Total leucocyte count (TLC), mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), blood glucose, total protein (TP), globulin, serum glutamate oxaloacetate transaminase (SGOT) and serum glutamate pyruvate transaminase (SGPT) were significantly (p < 0.05) high in negative control group when compared with positive control group. It could be concluded that Argulus infestation altered marked haematological and serum biochemical parameters. However, in treated groups complete elimination of Argulus was found in T4 and T5 groups. Also significant (p < 0.05) reduction in haematological and serum biochemical parameters of all the treatment groups were recorded in comparison with negative control group. In addition, T4 and T5 groups showed significantly (p < 0.05) high superoxide dismutase (SOD), catalase, total erythrocyte count (TEC) and haemoglobin (Hb). However, higher mean corpuscular haemoglobin concentration (MCHC), blood glucose and lactate dehydrogenase (LDH) levels in T5 group revealed that higher concentration of azadirachtin have notable effects on activity of vital tissues function and physiology of the host. Argulus spp. from infested goldfish could be eliminated using bath treatment with solution of azadirachtin having concentration of 15 mg L(-1) and that also shifted haematological and serum biochemical parameters towards homeostasis.

Effect of chloride on nitrite-induced methaemoglobinemia in Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus (Mitchill)

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.

Acute and sublethal effects in an Indian major carp Cirrhinus mrigala exposed to silver nitrate: Gill Na+/K+-ATPase, plasma electrolytes and biochemical alterations

Due to prolonged use of silver in many applications, it enters into the freshwater and affects the aquatic organisms. Fingerlings of Cirrhinus mrigala were exposed to acute and sublethal concentrations of silver nitrate and the alterations of gill Na(+)/K(+)-ATPase, plasma electrolytes and biochemical parameters were assessed. The median lethal concentration of silver nitrate to the fish C. mrigala for 96 h was found to be 0.107 mg/l (with 95% confidence limits). 1/10th of LC 50 96 h value (0.0107 mg/l) was selected for sublethal study. During acute treatment branchial Na(+)/K(+)-ATPase activity was inhibited approximately 44.34% after 96 h of exposure. In sublethal treatment, silver nitrate could not produce a significant change in the activity of the enzyme at the end of 7th day. However, after 14th day, significant (p < 0.05) decrease was noted showing 22.52%-49.11% in rest of the study period. Silver intoxication resulted hyponatremia, hypokalemia, hypochloremia, and hypoproteinemia in both the treatments. Despite the decrease in these parameters, plasma glucose level was found to be increased in both the treatments to endure the silver toxicity. We suggest that the alterations in branchial Na(+)/K(+)-ATPase activity, plasma electrolytes, and biochemical parameters of fish may be useful in environmental biomonitoring and to assess the health of fish in freshwater habitat contaminated with silver.

Toxicity of Moringa oleifera seed extract on some hematological and biochemical profiles in a freshwater fish, Cyprinus carpio

The study was carried out to investigate the acute and sublethal toxicity of Moringa oleifera seed extract on hematological and biochemical variables of a freshwater fish Cyprinus carpio under laboratory conditions. The 96 h LC50 value of M. oleifera seed extract to the fish C. carpio was estimated by probit analysis method and was found to be 124.0 mg/L (with 95% confidence limits). For sublethal studies a non lethal dose of 1/10th of 96 h LC50 value (12.40 mg/L) was taken. During acute treatment (96 h), hematological variables like red blood cell count (RBC), hemoglobin (Hb), hematocrit (Hct), and mean corpuscular hemoglobin concentration (MCHC) were significantly (P<0.05) decreased in fish exposed to seed extract. However a significant (P<0.05) increase in white blood cell count (WBC), mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH) value was observed in the exposed fish during above treatment period when compared to that of the control groups. Biochemical parameters such as plasma protein and glucose levels significantly declined in fish exposed to seed extract while a significant (P<0.05) increase in aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) activity was observed. During sublethal treatment (12.40 mg/L), WBC count, MCV, MCH, plasma glucose, AST, ALT and ALP activities were gradually elevated (P<0.05) at the end of 7, 14, 21, 28 and 35th days in seed extract exposed fish, whereas plasma protein level declined. However, a biphasic trend was noticed in Hb, Hct, RBC and MCHC levels. This study may provide baseline information about the toxicity of M. oleifera seed extract to C. carpio and to establish safer limit in water purification.

Effects of Roundup Transorb on fish: hematology, antioxidant defenses and acetylcholinesterase activity

Roundup Transorb(RDT) is a glyphosate-based herbicide containing a mixture of surfactants. The objective of this work was to evaluate the effects of this herbicide on the Neotropical fish Prochilodus lineatus. Juvenile fish were acutely exposed (6, 24 and 96 h) to 1 mg L(-1) of RDT (RDT 1), 5 mg L(-1) of RDT (RDT 5) or only water (control) and blood samples for hematological analysis, liver for antioxidants analysis, and brain and muscle for acetylcholinesterase (AChE) determination, were collected. RDT effects were more evident in fish exposed to the higher concentration of the herbicide. Hematologic alterations appeared only after 96 h exposure, when fish showed an increase in the hematocrit and in the number of both red and white blood cells. After 6h exposure fish showed a transient reduction in superoxide dismutase and catalase activity. RDT also inhibited glutathione-S-transferase, after 6 and 24h of exposure. The reduction in these enzymes is probably related to the occurrence of lipid peroxidation (LPO) in fish exposed to the herbicide for 6h. LPO returned to control levels after 24 and 96 h exposure to RDT, when fish showed an increased activity of glutathione peroxidase. The content of reduced glutathione also increased after 96 h exposure. Thus, after 24 and 96 h the antioxidant defenses were apparently enough to combat ROS, preventing the occurrence of oxidative damage. The exposure to RDT for 96 h led to an inhibition of AChE in brain and muscle at rates which may not be considered a life-threatening situation.

Individual and combined effects of heavy metals on serum biochemistry of Nile tilapia Oreochromis niloticus

Changes in serum biochemistry in response to single- and combined-metal exposure were studied in a freshwater fish Oreochromis niloticus. Fish were exposed to 5.0 mg/L Zn, 1.0 mg/L Cd, and 5.0 mg/L Zn+1.0 mg/L Cd mixtures for 7 and 14 days to determine levels of biochemical parameters and metals in blood serum. The individual and combined effects of metals caused an increase in alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities and in levels of albumin, transferrin, ceruloplasmin, cortisol, glucose, and total protein, whereas they caused a decrease in cholesterol levels. At both exposure periods, increased ALT activity of fish exposed to Cd was higher compared with the Zn and Zn+Cd groups, respectively. The decreased cholesterol level was higher in the Cd alone, and for Cd in combination with Zn, than in Zn alone at 14 days. Zn or Cd levels increased in the blood serum of fish exposed to metals individually or in combination. When fish were exposed to the mixtures of Zn+Cd, concentrations of these metals in their serum were lower than in fish exposed to individual metals. One metal blocks or even antagonizes the gill epithelium absorption of the other and thereby limits the distribution of the metal in blood. The results indicate that biochemical parameters in fish blood can be used as an indicator of heavy-metal toxicity.

Nitrite-induced methemoglobinaemia affects blood ionized and total magnesium level by hydrolysis of plasma adenosine triphosphate in rat

The objective of this study was to evaluate the effects of sodium nitrite (NaNO(2))-induced methemoglobinaemia on plasma ATP (adenosine triphosphate) and corresponding changes of blood-ionized magnesium (iMg(2+)) as well as total magnesium (tMg(2+)) in a time-dependent manner. This study was performed on male Sprague-Dawley rats to which NaNO(2) was injected (10 mg/kg i.p.) to induce methemoglobinaemia. Methemoglobin (MetHb) in blood was measured before (0 min.) and after 10, 30, 60 and 120 min. of NaNO(2) injection. At respective time points, the tMg(2+), blood ions and gases were measured by atomic absorption spectrometry and ion selective electrode, respectively. Haematological parameters were checked by automatic blood cell count, and blood films were observed under light microscope. Plasma ATP was measured by bioluminescence assay using a luminometer, and plasma proteins were measured by an automatic analyser. Blood cell count (RBC, WBC and platelet), haematocrit, and haemoglobin were found to be decreased with the advancement of MetHb concentration. With the gradual increase of MetHb concentration, the plasma ATP decreased and blood iMg(2+) and plasma tMg(2+) increased significantly as time passed by in comparison with the pre-drug values. A significant decrease of the ratio of ionized calcium to iMg(2+), Na(+) and increase of K(+) was observed. In conclusion, NaNO(2)-induced methemoglobinaemia is a cause of hydrolysis of plasma ATP which is responsible for the increase of blood iMg(2+) and plasma tMg(2+) in rats.

Acute effects of diflubenzuron on the freshwater fish Prochilodus lineatus

The effects of diflubenzuron (DFB), an insecticide to control ectoparasites in fish farms, on muscle acetylcholinesterase (AChE), detoxifying and antioxidant enzymes, hematological and physiological parameters, and liver histopathology were evaluated in Prochilodus lineatus after 6, 24 and 96 h of exposure to 25 mg L(-1) of DFB. The insecticide caused a reduction in the number of erythrocytes and hemoglobin content after 96 h exposure, probably due to hemolysis. Hyperglycemic response indicated energy mobilization, and may have contributed to the increase in osmolarity after 96 h exposure to DFB. The induction of glutathione-S-transferase (GST) and catalase activities in liver pointed to the activation of xenobiotic metabolic pathways and antioxidant defenses. The decrease in muscle AChE at all experimental times showed that DFB is an AChE inhibitor. In addition, DFB induced hepatic alterations that might impair normal liver functions. These results show that DFB can cause health disorders in fish and further studies are required to better define its safe use in aquaculture.

Biochemical, physiological, and histological changes in the neotropical fish Prochilodus lineatus exposed to diesel oil

Toxicity tests were conducted simulating a diesel oil spill in a tropical environment and juveniles of Prochilodus lineatus were exposed to the water-soluble fraction of diesel oil (WSD) for 6, 24, 96 h, and 15 days. The results showed the activation of biotransformation pathways for xenobiotics, through a time-dependent increase of liver GST activity. WSD caused a decrease in hematocrit and hemoglobin content, very likely due to hemolysis. Furthermore, an increase in glucose levels was observed after acute exposure to WSD. A possible lack of cortisol response could also be associated with WSD, since a reduction in plasma cortisol was seen in fish exposed to the petroleum product for 15 days. Moreover, the occurrence of lesions in the gills and even more severe lesions in the liver, should lead to functional damage to both organs, interfering thus directly with fundamental processes for the maintenance of homeostasis in this fish.

Acute lethal and sublethal effects of neem leaf extract on the neotropical freshwater fish Prochilodus lineatus

The aim of this study was to determine the toxicity of the aqueous extract of neem leaves, a product extensively used in fish-farms as alternative for the control of fish parasites and fish fry predators, for the neotropical fish Prochilodus lineatus. The 24 h LC(50) of neem leaf extract for juveniles P. lineatus was estimated as 4.8 g L(-1); the fish were then exposed for 24 h to 2.5, 5.0 and 7.5 g L(-1) or only clean water (control). Plasma glucose levels were higher in fish exposed to 2.5 g L(-1) and 5.0 g L(-1) neem extract, relative to control, indicating a typical stress response. Neem extract did not interfere with the osmoregulating capacity of the fish, as their plasma sodium, chloride, total protein and osmolarity did not change. The presence of the biopesticide interfered with the antioxidant defense system of P. lineatus, as there was a decrease in liver catalase activity at all neem concentrations and the detoxifying enzyme glutathione-S-transferase was activated in fish exposed to 5.0 g L(-1). Fish exposed to all neem extract concentrations exhibited damaged gill and kidney tissue. These results indicate that although neem extract is less toxic to P. lineatus than other synthetic insecticides used in fish-farming it does cause functional and morphological changes in this fish species.

Morphological changes in the kidney of a fish living in an urban stream

This study reports the incidence of histological alterations in the posterior kidney and morphometric changes in the interrenal tissue of the Neotropical fish Astyanax altiparanae collected from an urban stream impaired by anthropogenic activities and from a clean site (reference). The histological alterations observed in fish kidney from the disturbed stream were in complete contrast to those from the reference site, in respect of the type, severity and number of lesions observed. Tissue lesions found in fish from the urban stream were more severe and in some cases irreparable. The morphometric analysis of interrenal cells showed that fish from the urban stream exhibited increased cellular and nuclear areas and nuclear diameter, indicating hyperactivity of the interrenal cells, which is a sign of long-term stimulation of the hypothalamus-pituitary-interrenal axis. The high incidence of histological alterations in the kidney of A. altiparanae is an evidence of the poor environmental quality of this urban stream, while interrenal cells hypertrophy indicates that these fish are chronically exposed to stressors in their environment. Although the specific causative factors for the observed alterations are unknown this study demonstrates the application of kidney histopathology as a general quality indicator of the aquatic environment.

Biochemical and physiological biomarkers in Prochilodus lineatus submitted to in situ tests in an urban stream in southern Brazil

The aims of the present study were to verify the suitability of short-term in situ test with the neotropical fish Prochilodus lineatus and to evaluate from a set of biochemical and physiological biomarkers the ones which could work as sensitivity tools for the environmental quality assessment. In situ tests were carried out for 1 week in winter and summer, at three sites along an urban stream heavily contaminated by anthropogenic activities and at a reference site. The variables analyzed were: hemoglobin content (Hb), plasma concentrations of cortisol, glucose, total protein, Na(+) and Cl(-), plasma osmolarity, liver activities of glutathione-S-transferase (GST) and catalase and interrenal cells area. Results showed that glycemia, interrenal cell size and GST activity, which were significantly higher in fish caged in the urban stream, were best able to distinguish between the most disturbed sites and the reference and caged P. lineatus showed to be a promising tool for the assessment and monitoring of tropical aquatic ecosystems.

Health variables and gill morphology in the tropical fish Astyanax fasciatus from a sewage-contaminated river

The relative condition factor (Kn), gonadosomatic index (GSI), selected hematological variables and gill morphology of the fish Astyanax fasciatus were analyzed in two sites (site 1 was unpolluted and site 2 was polluted with untreated domestic sewage) of a tropical river (Camanducaia river, Sao Paulo State, Brazil). The relationship between the body mass (M(B)) and the standard length (L(S)) of A. fasciatus from both sites was M(B)=0.00799 L(S)(3.51843). The Kn values from both males and females and the GSI of females were significantly higher in site 2. The mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration were higher in females from site 2. Gill tissue anomalies and gill parasites were rare in fish from both sites; however, the number of chloride cells was significantly higher in fish from site 1. A. fasciatus presents high capacity to live in ion-poor and soft water and is able to compensate for environmental changes caused by untreated domestic sewage discharges.

Acute effects of sediments taken from an urban stream on physiological and biochemical parameters of the neotropical fish Prochilodus lineatus

Juveniles of Prochilodus lineatus were exposed to sediments collected from one of five sites along an urban stream into which various types of contaminants are discharged. After 24 or 96 h fish were examined and the results compared with those from control groups (fish exposed only to water, for the same period). Plasma ion levels varied significantly and fish exposed to site 5 sediment showed a transient increase in both sodium and chloride concentrations. Plasma glucose was significantly higher in fish exposed to sediment from sites 2 and 5. The higher liver glutathione-S-transferase activity registered in fish exposed to sediment from sites 1, 4 and 5 suggests the presence of organic contaminants at these sites and the enhancement of liver catalase activity in fish exposed to sediment from sites 3 and 4 may be due to contaminant-mediated oxyradical production. The overall results revealed that sites 4 and 5 are more severely contaminated, probably due to organic contaminants from agricultural sources and municipal landfill.