Tamoxifen induces biochemical responses in Pacific oysters Magallana gigas (Thunberg, 1793) at environmentally relevant concentrations.

The activities of catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), glucose-6-phosphate dehydrogenase (G6PDH), and glutathione-S-transferase (GST) were evaluated in the gills (GI) and digestive gland (DG) of Magallana gigas oysters exposed to tamoxifen (TAM) at environmental concentrations of 10 and 100 ng L-1 for 1 and 4 days. A higher CAT activity in the GI and DG and higher GPx activity only in the DG was observed of oysters exposed to both concentrations after 1 day. Furthermore, a significant increase in GR and G6PDH, was detected in the DG after 1 day of exposure to 10 ng L-1 and only G6PDH activity increase after 1 day of exposure to 10 ng L-1 in the GI. This suggests that the DG is a tissue more sensitive to TAM exposure and was confirmed with the individual Integrated Biomarker Response version 2 index (IBRv2i), highlighting the acute stress caused by TAM and a cellular adaptation.

Hepatic transcriptome, transcriptional effects and antioxidant responses in Poecilia vivipara exposed to sanitary sewage.

Aquatic environments are subject to threats from multiple human activities, particularly through the release of untreated sanitary sewage into the coastal environments. These effluents contain a large group of natural or synthetic compounds referred to as emerging contaminants. Monitoring the types and quantities of toxic substances in the environment, especially complex mixtures, is an exhausting and challenging task. Integrative effect-based tools, such as biomarkers, are recommended for environmental quality monitoring programs. In this study, fish Poecilia vivipara were exposed for 24 and 96 h to raw untreated sewage diluted 33 % (v/v) in order to identify hepatic genes to be used as molecular biomarkers. Through a de novo hepatic transcriptome assembly, using Illumina MiSeq, 54,285 sequences were assembled creating a reference transcriptome for this guppy species. Transcripts involved in biotransformation systems, antioxidant defenses, ABC transporters, nuclear and xenobiotic receptors were identified and evaluated by qPCR. Sanitary sewage induced transcriptional changes in AhR, PXR, CYP2K1, CYP3A30, NQO1, UGT1A1, GSTa3, GSTmu, ST1C1, SOD, ABCC1 and SOX9 genes from liver of fish, particularly after 96 h of exposure. Changes in hepatic enzyme activities were also observed. The enzymes showed differences in fish exposed to both periods, while in the gills there was a prevalence of significant results after 96 h. The observed differences were associated to gender and/or to sewage exposure. The obtained results support the use of P. vivipara as sentinel and model organism for ecotoxicological studies and evidence the importance of understanding the differential responses associated to gender.

Biochemical and molecular biomarkers and their association with anthropogenic chemicals in wintering Manx shearwaters (Puffinus puffinus).

Anthropogenic pollution poses a threat to marine conservation by causing chronic toxic effects. Seabirds have contact throughout their lives with pollutants like plastic, metals, polychlorinated biphenyls (PCBs), and organochlorine pesticides such as hexachlorocyclohexanes (HCHs). We assessed 155 Manx shearwaters (Puffinus puffinus) stranded along the Brazilian coast, analyzing associations between organic pollutants, plastic ingestion, biomarkers (transcript levels of aryl hydrocarbon receptor, cytochrome P450-1A-5 [CYP1A5], UDP-glucuronosyl-transferase [UGT1], estrogen receptor alpha-1 [ESR1], and heat shock protein-70 genes) and enzymes activity (ethoxy-resorufin O-deethylase and glutathione S-transferase [GST]). Plastic debris was found in 29 % of the birds. The transcription of UGT1 and CYP1A5 was significantly associated with hexachlorobenzene (HCB) and PCBs levels. ESR1 was associated with HCB and Mirex, and GST was associated with Drins and Mirex. While organic pollutants affected shearwaters more than plastic ingestion, reducing plastic availability remains relevant as xenobiotics are also potentially adsorbed onto plastics.

Transcriptomic investigation and biomarker discovery for zinc response in oysters Crassostrea gasar.

In an era of unprecedented industrial and agricultural growth, metal contamination in marine environments is a pressing concern. Sentinel organisms such as the mangrove oyster Crassostrea gasar provide valuable insights into these environments' health. However, a comprehensive understanding of the molecular mechanisms underlying their response to metal exposure remains elusive. To address this gap, we reanalyzed the 454-sequencing data of C. gasar, utilizing an array of bioinformatics workflow of CDTA (Combined De Novo Transcriptome Assembly) to generate a more representative assembly. In parallel, C. gasar individuals were exposed to two concentrations of zinc (850 and 4500 µg L-1 Zn) for 48 h to understand their molecular responses. We utilized Trinotate workflow for the 11,684-CDTA unigenes annotation, with most transcripts aligning with the genus Crassostrea. Our analysis indicated that 67.3% of transcript sequences showed homology with Pfam, while 51.4% and 54.5%, respectively had GO and KO terms annotated. We identified potential metal pollution biomarkers, focusing on metal-related genes, such as those related to the GSH biosynthesis (CHAC1 and GCLC-like), to zinc transporters (ZNT2-like), and metallothionein (MT-like). The evolutionary conservation of these genes within the Crassostrea genus was assessed through phylogenetic analysis. Further, these genes were evaluated by qPCR in the laboratory exposed oysters. All target genes exhibited significant upregulation upon exposure to Zn at both 850 and 4500 µg L-1, except for GCLC-like, which showed upregulation only at the higher concentration of 4500 µg L-1. This result suggests distinct activation thresholds and complex interactions among these genes in response to varying Zn concentrations. Our study provides insights into the molecular responses of C. gasar to Zn, adding valuable tools for monitoring metal pollution in marine ecosystems using the mangrove oyster as a sentinel organism.

Ingestion and depuration of polyester microfibers by Crassostrea gasar (Adanson, 1757).

The study aimed to obtain environmentally relevant microfibers (MFs) from polyester fabric and assess their impact on the oyster Crassostrea gasar. MFs were obtained by grinding the fabric, and their accumulation in oysters gills and digestive glands was analyzed after exposure to 0.5 mg/L for 2 and 24 h. Additionally, a 48 h depuration was conducted on the oysters exposed for 24 h. Sublethal effects were assessed in oysters exposed for 24 h and depurated for 48 h, using biomarkers like Catalase (CAT), Glutathione S-transferase (GST), and Glutathione Peroxidase (GPx), along with histological analyses. Polyester fabric grinding produced significant MFs (average length: 570 µm) with degraded surface and increased malleability. Oysters showed increased MF accumulation in digestive glands post-exposure, with no impact on antioxidant enzymes. Depuration decreased MFs accumulation. Histological analysis revealed accumulation in the stomach and brown cells, possibly indicating inflammation. This raises concerns about MFs bioaccumulation in marine organisms, impacting the food chain and safety.

Emerging and legacy contaminants on the Brazilian southern coast (Santa Catarina): A multi-biomarker approach in oysters Crassostrea gasar (Adanson, 1757).

Coastal environments, such as those in the Santa Catarina State (SC, Brazil), are considered the primary receptors of anthropogenic pollutants. In this study, our objective was to evaluate the levels of emerging contaminants (ECs) and persistent organic pollutants (POPs) in indigenous Crassostrea gasar oysters from different regions of SC coast in the summer season (March 2022). Field collections were conducted in the São Francisco do Sul, Itajaí, Florianópolis and Laguna coastal zones. We analyzed the bioaccumulation levels of 75 compounds, including antibiotics (AB), endocrine disruptors (ED), non-steroidal anti-inflammatory drugs (NSAIDs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and pesticides. Furthermore, we assessed biomarker responses related to biotransformation, antioxidant defense, heat shock protection and oxidative damage in oysters' gills. Prevalence of ECs was observed in the central and southern regions, while the highest concentrations of POPs were detected in the central-northern regions of SC. Oysters exhibited an induction in biotransformation systems (cyp2au1 and cyp356a1, sult and GST activity) and antioxidant enzymes activities (SOD, CAT and GPx). Higher susceptibility to lipid peroxidation was observed in the animals from Florianópolis compared to other regions. Correlation analyses indicated possible associations between contaminants and environmental variables in the biomarker responses, serving as a warning related to climate change. Our results highlight the influence of anthropogenic activities on SC, serving as baseline of ECs and POPs levels in the coastal areas of Santa Catarina, indicating more critical zones for extensive monitoring, aiming to conserve coastal regions.

Biochemical responses in Pacific oysters Magallana gigas (Thunberg, 1793): Tools to evaluate the environmental quality of aquaculture areas.

The discharge of sanitary sewage into the bays of the Florianópolis Metropolitan Area (Southern Brazil), has led to the contamination of oyster farms. Consequently, linear alkylbenzenes (LABs) were quantified in the sediment, and the biochemical responses in gills and digestive gland of oysters from six farms were assessed. Our findings revealed elevated levels of LABs in the sediment of the Imaruim and Serraria farms. Additionally, alterations were observed in the antioxidant enzymes: catalase, glutathione peroxidase and superoxide dismutase in both oyster tissue from the Serraria, Santo Antonio de Lisboa and Sambaqui farms. Furthermore, correlation analyses indicated strong and moderate associations between biochemical responses, organic contaminants, and certain physicochemical parameters. Consequently, our results demonstrated the activation of the antioxidant system in oysters, representing a protective response to the presence of sanitary sewage and other contaminants. Therefore, we propose the utilization of biochemical biomarkers for monitoring the environmental quality of farms.

Prednisone and prednisolone effects on development, blood, biochemical and histopathological markers of Aquarana catesbeianus tadpoles.

Synthetic glucocorticoids are often found in surface waters and can cause harmful effects to aquatic organisms such as amphibians. In this work we evaluated the effects of the drugs prednisone (PD) and prednisolone (PL) on developmental, molecular, blood, biochemical and histological markers. Aquarana catesbeianus tadpoles were exposed for 16 days to environmentally relevant concentrations of 0, 0.1, 1 and 10 µg/L of both drugs. PD increased the transcript levels of the enzyme deiodinase III (Dio3), the hormones cortisol and T4 and delayed development. Changes in the thyroid gland occurred after tadpoles were exposed to both drugs, with a reduction in the diameter and number of follicles and an increase/or decrease in area. Also, both drugs caused a decrease in lymphocytes (L) and an increase in neutrophils (N), thrombocytes, the N:L ratio and lobed and notched erythrocytes. Increased activity of the enzymes superoxide dismutase, glutathione S-transferase and glucose 6-phosphate dehydrogenase was observed after exposure to PD. Furthermore, both drugs caused an increase in the activity of the enzymes catalase and glutathione peroxidase. However, only PD caused oxidative stress in exposed tadpoles, evidenced by increased levels of malondialdehyde and carbonyl proteins. Both drugs caused an increase in inflammatory infiltrates, blood cells and melanomacrophages in the liver. Our results indicate that PD was more toxic than PL, affecting development and causing oxidative stress.

Integrating pollutant levels and biochemical biomarkers in oysters (Crassostrea rhizophorae and Crassostrea gasar) indicates anthropic impacts on marine environments along the coast of Santa Catarina state, Brazil.

This study aimed to carry out a general diagnosis of the contamination of the coastal marine environment of the Santa Catarina state (SC, Brazil) by different classes of environmental pollutants, as well as to evaluate possible adverse effects of the contaminants on biochemical biomarkers of oysters, Crassostrea gasar and Crassostrea rhizophorae. 107 chemicals were evaluated in water, sediment and oyster samples from nine sites along the coastline of SC. We also examined various biochemical biomarkers in the oysters' gills and digestive glands to assess potential effects of contaminants. In general, the northern and central regions of the littoral of SC presented higher occurrences and magnitudes of contaminants than the southern region, which is probably related to higher urbanization of center and northern areas of the littoral. The biomarker analysis in the oysters reflected these contamination patterns, with more significant alterations observed in regions with higher levels of pollutants. Our results may serve as a first baseline for future and more extensive monitoring actions and follow-up of the degree of contamination in the state, allowing for inspection actions and management of areas most affected by marine pollutants.

Biochemical responses of the mussel Perna perna after exposure to environmental concentrations of the UV filter Benzophenone-3.

Personal care products, such as UV filters, are frequently present in aquatic ecosystems, but studies on their impact on marine organisms are still scarce. Here we addressed the effects of benzophenone-3 (BP-3) on the antioxidant status of Perna perna mussels exposed to concentrations of 0.1 and 3 µg.L-1 for 72 h and 7 days. Glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), glucose-6-phosphate dehydrogenase (G6PDH) activity and lipoperoxidation (MDA) were evaluated in the gills. A significant reduction (p < 0.05) in the activity of G6PDH and GPx was observed after exposure for 7 days to 0.1 µg.L-1. However, no significant differences were observed in GST activity and MDA levels, independently of the exposure time. Principal component analysis (PCA) showed an association of BP-3 highest concentration with GR and MDA at 72 h and only with GR at 7 days of exposure. Similarly, the integrated biomarker response (IBR) demonstrated GR and MDA alterations. In conclusion, environmentally relevant concentrations of BP-3 altered antioxidant and auxiliary enzymes, which could cause long-term damage to P.perna mussels. The need to implement more efficient techniques in wastewater treatment systems is pointed out, especially in summer, when UV filters are used more frequently and abundantly.

Comparative biochemical and molecular responses of biotransformation and antioxidant systems in three species of Crassostrea (Sacco, 1897) oysters exposed to chrysene.

Chrysene (CHR) is among the most persistent polycyclic aromatic hydrocarbons (PAH) in water and a priority compound for pollutants monitoring, due to its carcinogenic, mutagenic and genotoxic potential. Aquatic animals exposed to CHR may present alterations of biomarkers involved in the biotransformation and oxidative stress-related parameters. The aim of this study was to investigate differences in antioxidant and biotransformation (phase I and II) systems of Crassostrea gigas, C. gasar and C. rhizophorae and its effects resulting from CHR exposure. Adult oysters of these species were exposed to 10 µg L-1 of CHR for 24 h and 96 h. In gills, the transcripts CYP1-like, CYP2-like, CYP2AU1-like, GSTO-like, MGST-like, SULT-like were evaluated after 24 h of exposure. The activity of SOD, CAT, GPx, GR and G6PDH were analyzed in gills and digestive glands after 96 h of exposure. CHR bioaccumulated in tissues. Differences in the remaining levels of CHR in water after 96 h were observed in aquaria containing C. gigas or C. gasar oysters and may be associated to the different filtration rates between these species. Downregulate of biotransformation genes were observed in gills of C. gasar (CYP2AU1-like and GSTO-like) and C. rhizophorae (CYP1-like1, CYP2-like, MGST-like and SULT-like), suggesting that biotransformation responses may be species-specific. Differential activity of antioxidant enzymes were observed in gills and digestive gland of oysters exposed to CHR. Biochemical responses suggested that C. gigas and C. gasar are more responsive to CHR. Differential responses observed among the three Crassostrea species can be related to evolutionary differences, ecological niches and adaptation to environment.

Effects of cadmium and zinc on gene expression of novel molecular biomarkers in the mangrove oyster Crassostrea gasar.

Metal contamination impacts various aquatic species, and mollusk bivalves are appropriate sentinel organisms in coastal pollution assessment. Metal exposure can disrupt homeostasis, alter gene expression, and harm cellular processes. However, organisms have evolved mechanisms to regulate metal ions and counteract their toxicity. This study examined the effect of acute cadmium (Cd) and zinc (Zn) on metal-related gene expression in gills of Crassostrea gasar following 24 and 48 h of laboratory exposure. We focused on Zn transport, metallothionein (MT), glutathione (GSH) biosynthesis, and calcium (Ca) transporter genes to understand the underlying Cd and Zn-accumulating mechanisms that prevent metal toxicity. Our findings revealed increased Cd and Zn levels in oyster gills, with significantly higher accumulation after 48 h. C. gasar accumulated high Cd concentrations even in scarce conditions and increased Zn levels, suggesting a strategy to cope with toxicity. While no significant gene expression differences were observed after 24 h, the increased metal accumulation after 48 h led to upregulation of CHAC1, GCLC, ZnT2, and MT-like genes in oysters exposed to Cd, and increased ZnT2-like expression following exposure to higher Cd/Zn mixtures. We found evidence of oysters may mobilize metal-related genes to mitigate Cd-induced toxicity by both chelating metals and/or reducing their intracellular concentrations. The observed genes upregulation also indicates their sensitivity to changes in metal bioavailability. Overall, this study offers insights into oyster mechanisms for coping with metal toxicity and suggests ZnT2, MT, CHAC1, and GCLC-like as molecular biomarkers for monitoring aquatic metal pollution using C. gasar as sentinel species.

Effects of the herbicide ametryn on development and thyroidogenesis of bullfrog tadpoles (Aquarana catesbeiana) under different temperatures.

Thyroid hormones (TH) are essential for the metamorphosis of amphibians and their production can be influenced by environmental stressors, such as temperature fluctuations, and exposure to aquatic pollutants, such as herbicides. In the present study we evaluated the influence of different temperatures (25 and 32 °C) on the effects of the herbicide ametryn (AMT, 0 - control, 10, 50 and 200 ng.L-1) for 16 days on thyroidogenesis of bullfrog tadpoles. Higher temperature and AMT exposure caused a delay in the development of tadpoles, despite no differences were noted in weight gain and total length of the animals. Levels of triiodothyronine (T3) and thyroxine (T4) were not altered neither by AMT nor by temperature, but the highest temperature caused a decrease in total area and number of follicles in the thyroid gland. Transcript levels of thyroid hormone receptors alpha and beta (TRα and TRß) and iodothyronine deiodinase 3 (DIO3) were lower at 32 °C, which is consistent with developmental delay at the higher temperature. Tadpoles exposed to 200 ng.L-1 of AMT at 25 °C also presented delayed development, which was consistent with lower TRα and DIO3 transcript levels. Lower levels of estradiol were noted in tadpoles exposed to AMT at the higher temperature, being also possibly related to a developmental delay. This study demonstrates that higher temperature and AMT exposure impair thyroidgenesis in bullfrog tadpoles, disrupting metamorphosis.

Fipronil impairs the GABAergic brain responses of Nile Tilapia during the transition from normoxia to acute hypoxia.

γ-aminobutyric acid (GABA) is one of the main neurotransmitters involved in the adaptation processes against the damage that hypoxia can cause to the brain. Due to its antagonist action on GABA receptors, the insecticide fipronil can turn the fish more susceptible to the negative effects of hypoxia. This study aimed to understand better if fipronil affects these GABAergic responses of Tilapia ahead to hypoxia. Oreochromis Niloticus (Nile Tilapia) were exposed for 3 and 8 h to fipronil (0.0, 0.1, and 0.5 µg.L-1 ) under normoxia (dissolved O2 > 6 mg.L-1 ) and moderate hypoxia (dissolved O2 < 2 mg.L-1 ) conditions. Briefly, hypoxia caused opposite effects on the gene transcription of the evaluated ionotropic and metabotropic GABA receptors. Unexpectedly, we obtained reduced HIF1A mRNA and brain GABA levels, mostly in the first 3 h of the experiment, for the hypoxic group compared with the normoxia one. Besides that, we also demonstrated that the insecticide fipronil impairs the brain GABAergic signaling of a hypoxia-tolerant fish during the transition from a normoxic to an acute hypoxic state. Thus, these results predict the relevant impact on the brain metabolic adaptations of fishes exposed to such stressful conditions in an aquatic environment, as well as the effects of fipronil in the GABAergic responses to hypoxia, which in turn may have ecological and physiological significance to hypoxia-tolerant fishes exposed to this insecticide.

Microplastics and linear alkylbenzene levels in oysters Crassostrea gigas driven by sewage contamination at an important aquaculture area of Brazil.

The levels of linear alkylbenzenes (LABs) and the occurrence of microplastics (MPs) in the oysters Crassostrea gigas were evaluated in six farming areas in southern Brazil. The results revealed higher concentrations of LABs in oyster tissue from the Serraria (1977 ± 497.7 ng g-1) and Imaruim (1038 ± 409.9 ng g-1) sites. Plastic microfibers were found in oysters from all locations with values from 0.33 to 0.75 MPs per oyster (0.27-0.64 MPs per gram) showing the ubiquitous presence of this contaminant in the marine environment, which could be considered a threat to farming organisms. In addition, elements such as Ti, Al, Ba, V, Rb, Cr, and Cu were found in the chemical composition of the microfibers, suggesting MPs as vectors of inorganic compounds. A positive correlation between LABs and thermotolerant coliforms suggests that sewage discharges are the main source of contamination in these oysters cultured for human consumption. The present study highlights the need for efficient wastewater treatment plants and the implementation of depuration techniques in oysters from farming areas.

Molecular changes in oysters Crassostrea gigas (Thunberg, 1793) from aquaculture areas of Santa Catarina Island bays (Florianópolis, Brazil) reveal anthropogenic effects.

Anthropogenic activities in coastal regions cause risks to the environmental and human health. Due to the carcinogenic and mutagenic potential, polycyclic aromatic hydrocarbons (PAH) are considered priority for monitoring. Most of the Brazilian production of Crassostrea gigas oysters are placed in the Bays of Santa Catarina Island. The aim of this study was to evaluate molecular responses (phase I and II of biotransformation and antioxidant defense) of C. gigas from six oyster farming areas potentially contaminated by sanitary sewage in Florianópolis Metropolitan (SC, Brazil): Santo Antônio de Lisboa, Sambaqui, Serraria, Caieira, Tapera, Imaruim. We evaluated the transcript levels of CYP1A1-like, CYP2-like, CYP2AU2-like, CYP356A1, GSTA1A-like, GSTO.4A-like, SULT-like, SOD-like and CAT-like by qRT-PCR. Only oysters from Caieira showed levels of thermotolerant coliforms allowed by the law. Chemicals analyses in soft tissues of oysters showed low to average levels of PAH in all monitored areas. Enhanced transcript levels of phase I (CYP1A1-like, CYP3564A1-like, CYP2-like and CYP2AU2-like) were observed in oysters from Serraria and Imaruí, suggesting higher biotransformation activity in these farming areas. Regarding phase II of biotransformation, GSTO.4A-like was up-regulated in oysters from Imaruí compared to Caieira and Santo Antônio de Lisboa. An upregulation of SOD-like and CAT-like were observed in oysters from Imaruí and Serraria, suggesting that oysters from these sites are facing higher prooxidant conditions compared to other areas. By integrating the biological and chemical data it is suggested that human-derived contaminants are affecting the oyster metabolism in some farming areas.

Influence of temperature on growth, development and thyroid metabolism of American bullfrog tadpoles (Lithobates catesbeianus) exposed to the herbicide tebuthiuron.

The influence of temperature (25 and 32 °C) on the negative effects of the herbicide tebuthiuron (TBU, 0, 10, 50 and 200 ng.L-1, 16 days) on thyroid function and metamorphosis of Lithobates catesbeianus tadpoles was evaluated. Metamorphosis was accelerated by TBU exposure at 25 ºC, but delayed at 32 ºC with considerable losses of body mass. T3 and T4 levels were not altered. The highest TBU concentrarion at 25 ºC increased TRâ€¯ß and DIO3 transcript levels, which is consistent with development acceleration in tadpoles. At 32 ºC TRâ€¯ß transcript levels were lower than the values recorded at 25 ºC, and those tadpoles exposed to the highest TBU concentration presented increased diameter of thyroid follicles compared to controls at same temperature. This study evidences that TBU at environmentally realistic concentrations is able to disrupt thyroidogenesis in bullfrog tadpoles, impairing their development. These effects are influenced by temperature.

Influence of temperature on biomarker responses and histology of the liver of American bullfrog tadpoles (Lithobates catesbeianus, Shaw, 1802) exposed to the herbicide Tebuthiuron.

Tebuthiuron (TBU) is a phenylurea herbicide that is extensively used in sugarcane fields. Owing to the low degradation rate, high water solubility, and leaching potential, TBU is believed to have harmful effects on aquatic organisms, such as anuran tadpoles. Contaminant effects can be influenced by temperature since increases in temperature are often associated with increased metabolic reactions. In this study, we evaluated the influence of temperature on the negative effects of TBU in bullfrog tadpoles (Lithobates catesbeianus) through a multi-biomarker approach. Tadpoles were exposed to 0 (control) 10, 50, and 200 ng L-1 of TBU for 16 days at 25 and 32 °C. TBU increased the transcript levels of genes involved in biotransformation (glutathione S-transferase, GST, and sulfotransferase, SULT) and antioxidant (superoxide dismutase, SOD, and catalase, CAT) enzymes. TBU exposure also increased CAT and glutathione peroxidase (GPx) activities, whereas SOD and carboxylesterase activities were decreased. The highest temperature caused a decrease in the activities of ethoxyresorufin-O-deethylase and SOD but increased the activities of GST, GPx, glucose 6-phosphate dehydrogenase, and acetylcholinesterase. No effects of temperature or TBU exposure were observed in genotoxic markers (frequencies of micronucleous and nuclear abnormalities) or in lipid peroxidation levels. Tadpoles exposed to TBU at all tested concentrations presented a higher index of biomarker responses than that of the control groups. Higher values of severity scores from histological analyses were found in the liver of tadpoles exposed to 50 and 200 ng L-1 of TBU at 32 °C compared with those of the control group at the same temperature. These results indicate that TBU and temperature increases are able to disturb the metabolic homeostasis of L. catesbeianus tadpoles after 16 days of exposure, causing substantial alterations in biomarker responses and liver morphology.

Integrated biomarker responses in oysters Crassostrea gasar as an approach for assessing aquatic pollution of a Brazilian estuary.

The Laguna Estuarine System (LES), southern Brazil, suffers impacts from anthropogenic activities, releasing contaminants into the ecosystem. This study evaluated changes in biochemical and molecular biomarkers and contaminants concentrations in oysters Crassostrea gasar transplanted and kept for 1.5 and 7 days at three potentially contaminated sites (S1, S2, and S3) at LES. Metals varied spatiotemporally; S1 exhibited higher Ag and Pb concentrations, whereas Cd was present in S3. S2 was a transition site, impacted by Ag, Pb, or Cd, depending on the period. Organic contaminants concentrations were higher before transplantation, resulting in the downregulation of biotransformation genes transcripts levels. Phase II-related genes transcripts and metals showed positive correlations. Decreased levels of HSP90-like transcripts and antioxidant enzymes activity were related to increased pollutant loads. Integrated biomarker response index (IBR) analysis showed S1 and S3 as the most impacted sites after 1.5 and 7 days, respectively. Regardless of the scenario, LES contaminants pose a significant threat to aquatic biota.

Decreased malondialdehyde levels in fish (Astyanax altiparanae) exposed to diesel: Evidence of metabolism by aldehyde dehydrogenase in the liver and excretion in water.

Increased malondialdehyde (MDA) levels are commonly considered an indicator of lipid peroxidation derived from oxidative stress insults promoted by exposure of fish to pollutants. However, a decrease in MDA levels after xenobiotic exposure has been also reported, an effect that is mostly attributed to enhanced antioxidant defenses. In this study, we assessed whether pollutant-mediated MDA decrease would be associated with antioxidant enhancement or with its metabolism by aldehyde dehydrogenase (ALDH) in the liver and gills of lambari (Astyanax altiparanae) exposed to diesel oil (0.001, 0.01, and 0.1 mL/L). MDA levels were decreased in the liver of lambari exposed to diesel. The activities of the antioxidant enzymes, catalase (CAT) and glutathione peroxidase (GPx), were unchanged in the liver, while that of glucose-6-phosphate dehydrogenase (G6PDH) was decreased. In contrast, levels of total glutathione (tGSH) and the activity of glutathione S-transferase (GST) were increased in the liver, which partly support antioxidant protection against lipid peroxidation. More importantly, ALDH activity increased in a concentration-dependent manner, being negatively correlated with MDA levels, indicating MDA metabolism by ALDH. In the gills, diesel exposure increased MDA and lipid hydroperoxide levels, and promoted increases in antioxidant defenses, indicating oxidative stress. Curiously, ALDH activity was undetectable in the gills, supporting the possibility of direct MDA excretion in the water by the gills. Analyses of MDA in the water revealed increased levels of MDA in the aquaria in which the fish were exposed to diesel, compared to control aquaria. A second experiment was carried out in which the fish were intraperitoneally injected with MDA (10 mg/kg) and analyzed after 1, 6, and 12 h. MDA injection caused a time-dependent decrease in hepatic MDA levels, did not alter ALDH, CAT, GPx, and GST activities, and decreased G6PDH activity and tGSH levels. In the gills, MDA injection caused a slight increase in MDA levels after 1 h, but did not alter GPx, G6PDH, and GST activities. MDA injection also enhanced CAT activity and tGSH levels in the gills. MDA concentration in water increased progressively after 1, 6, and 12 h, supporting the hypothesis of direct MDA excretion as an alternative route for MDA elimination in fish. Our results suggest that the decreased MDA levels after exposure of lambari to diesel oil pollutant probably reflects an association between enhanced antioxidant protection, MDA metabolism, and MDA excretion in water.