Low concentration of 2,4,6-tribromophenol (TBP) represents a risk to South American silver catfish Ramdia quelen (Quoy and Gaimard, 1824) population.

The 2,4,6-tribromophenol (TBP) is an environmental persistent pollutant widely used as flame retardant, antimicrobial and insecticide agent in wood preservation and plastic production. Currently, TBP is found in environmental compartments such as soil, freshwater, groundwater, sewage sludge and domestic dust, but the effects to biota and the risk of exposure to aquatic vertebrates are still scarce. In the present study, Rhamdia quelen fish embryos (8 h post-fertilization - hpf) were exposed to 0.3 and 3.0 µg L-1 of TBP until 96 hpf. Biochemical biomarkers, hatching, survival and larvae/embryo malformations were evaluated after exposure. Additionally, a mathematical model was proposed to evaluate the effects along further generations. The results showed that TBP decreased the survival level but did not cause significant difference in the hatching rates. After 72 and 96 hpf, individuals from the highest tested concentration group showed more severe malformations than individuals from control and the lower concentrations groups. The deformities were concentrated on the embryos facial region where the sensorial structures related to fish behavior are present. The biochemical biomarkers revealed both oxidative stress and neurotoxicity signs after exposure to the contaminant, while the application of the mathematical model showed a decrease of population in both tested TBP concentrations. In conclusion, the current results demonstrated that TBP is toxic to R. quelen embryos and represents a risk to population after early life stage exposure.

Comparative bioaccumulation and effects of purified and cellular extract of cylindrospermopsin to freshwater fish Hoplias malabaricus.

Many tropical freshwater ecosystems are impacted by cyanobacteria blooms increasing the risk of cyanotoxins exposure to aquatic organisms while human populations may be exposed by eating fish, drinking water, or dermal swimming. However, few toxicological data are available on the influence of cyanobacteria blooms in particular, cylindrospermopsin (CYN) on Brazilian neotropical fish. A number of studies demonstrated the ability of CYN to bioaccumulate in freshwater organisms and consequently enter the human food chain. The aim of the current study was to examine the effects of CYN following single intraperitoneal injection (50 µg/kg) of purified CYN (CYNp) or aqueous extract of CYN-producing cyanobacteria extract (CYNex) after 7 or 14 days. Biomarkers such as histopathology (liver), oxidative stress (liver and brain), and acetylcholinesterase (AChE) activity (muscle and brain) were utilized in order to assess the influence of CYN on Hoplias malabaricus. In terms of AChE activity, administration of CYNex and CYNp both muscle and brains were used as target tissues. In brain an increase of glutathione S-transferase (GST) activity and lipid peroxidation (LPO) levels was noted suggesting an imbalance in redox cycling. The majority of biomarkers did not present significant alterations in liver, but an elevation in superoxide dismutase (SOD) and glucose 6 phosphate dehydrogenase (G6PDH) activities was found. Different profiles of GST activity were observed in both studied groups (CYNex and CYNp) while LPO (CYNex and CYNp) and protein carbonylation (PCO) (CYNp) levels increased after exposure to CYN. The incidence of necrosis, melanomacrophages centers, and free melanomacrophages were detected as evidence of cell death and immune responses. Nonprotein thiols (NPT) levels were not markedly affected in both exposed groups. Data demonstrated that in vivo exposure to CYN produced biochemical and morphological disturbances in liver and brain of H. malabaricus.

Mixtures of benzo(a)pyrene, dichlorodiphenyltrichloroethane and tributyltin are more toxic to neotropical fish Rhamdia quelen than isolated exposures.

The effects of benzo(a)pyrene (BaP), dichlorodiphenyltrichloroethane (DDT) and tributyltin (TBT) association were investigated through a multi-biomarker approach. Ten Rhamdia quelen fish per group were exposed through intraperitoneal injections either to BaP (0.3; 3 or 30 mg kg(-1)), DDT or TBT (0.03; 0.3 or 3 mg kg(-1)) or BaP/DDT, BaP/TBT, DDT/TBT or BaP/DDT/TBT on their lowest doses. The experiments were divided in acute (one dose, 5-day) and sub-chronic (3 doses, 15-day). Control groups received an equal volume of PBS or canola oil (1 ml kg(-1)). The three tested contaminants altered AChE activity in brain and muscle in similar ways; the mixtures antagonized the increase evoked by the contaminants alone. BaP and TBT increased GSH content and mixtures reduced it. GPx activity was increased by DDT and TBT in the 15-day experiment and reduced by the mixtures. BaP increased GST activity in sub-chronic experiment while TBT reduced it in the acute experiment. BaP/TBT increased GST activity compared to all groups; the other mixtures reduced it compared to BaP or DDT in the 5-day experiment. BaP, DDT and TBT increased δ-ALAd activity mainly in acute exposure; the mixtures also increased δ-ALAd compared to DDT or TBT in 5 and 15-day. BaP, TBT and BaP/DDT decreased LPO in the acute experiment. In the sub-chronic experiment DDT/TBT increased LPO when compared to TBT. None of the contaminants alone altered PCO, but all mixtures increased it compared to one or another contaminant. Contaminants isolated had a more acute effect in ALT plasma level; their lowest dose, which had no effect alone, in combination has led to an increase of this enzyme, especially after 15 days. DDT increased AST in the acute and sub-chronic experiments, while TBT did the same in the latter. DDT/TBT decreased AST opposing the effect of the contaminants alone in the 5-day experiment. Hepatic lesions index could be explained by a more acute effect of the contaminants alone or combined and by activation of cell defenses after the sub-chronic exposure. TBT increased melanomacrophages counting in the 5-day experiment and the mixtures increased it in the 5 and 15-day experiments. Overall, the majority of the biomarkers pointed to a more toxic effect when these contaminants were combined, leading to unexpected toxicities compared to individual exposure scenarios. These findings are relevant considering environmental exposure conditions, since organisms are often exposed to different combinations of contaminants.

Complex metabolic interactions between benzo(a)pyrene and tributyltin in presence of dichlorodiphenyltrichloroethane in South American catfish Rhamdia quelen.

In an attempt to explore complex metabolic interactions between toxicants present in polluted freshwater, hepatic metabolism of benzo(a)pyrene (BaP) and tributyltin (TBT) in fish was investigated when these compounds were administrated alone, mixed together and along with dichlorodiphenyltrichloroethane (DDT). Ten Rhamdia quelen per group were treated with a single intra-peritoneal (IP) dose (5-day experiment) or three successive doses (15-day experiment) either containing BaP (0.3; 3 or 30mgkg(-1)) or TBT (0.03; 0.3 or 3mgkg(-1)) or a combination of BaP+TBT, BaP+DDT, TBT+DDT and BaP+TBT+DDT under their respective lower doses, with DDT dose kept at 0.03mgkg(-1). Tetrahydroxy-benzo(a)pyrene (BaP-tetrol-I), and dibutyltin (DBT) and monobutyltin (MBT) were analyzed to assess BaP and TBT hepatic metabolism, respectively. A significant difference in BaP-tetrol-I concentration was observed in liver and bile between the lowest and the highest doses of BaP in both 5 and 15-day experiments. In the 15-day experiment, the presence of TBT with BaP reduced the amount of BaP-tetrol-I in bile compared to the BaP alone. The time of exposure and the number of doses affected BaP-tetrol-I concentration in the bile of fish exposed to BaP 0.3mgkg(-1) and BaP+DDT. TBT and its metabolites concentrations showed a dose-dependent increase in the liver in both experiments and in the bile in the 5-day experiment. TBT at its lowest dose was completely metabolized into DBT and MBT in the liver in the 15-day experiment. No TBT metabolites were detected in the bile of fish exposed to the mixtures in the 5-day experiment, except for a small MBT amount found in BaP+TBT+DDT. This study strengthens the hypothesis of a metabolic interaction between BaP and TBT in fish and suggests DDT as an important third player when present in the mixture.

From molecular endpoints to modeling longer-term effects in fish embryos exposed to the elutriate from Doce River.

Sediments represent a major sink and also a main source of contaminants to aquatic environments. An environmental disaster from a mining dam breakage in 2015 in South-East Brazil re-suspended complex mixtures of chemicals deposited in the sediment, spreading contaminants along the Doce River Basin (DRB) major river course. While high levels of contaminants in sediment were well described, toxicological effects in aquatic organisms were poorly investigated. Thus, the effects of these potentially toxic chemicals were assessed in the present study through different endpoints (biochemical to populational levels) in fish embryos of the South-American silver catfish exposed to elutriates from different sites of the DRB. Despite no significant mortality observed, our results showed that exposure to the elutriates, especially those from the closest site to the dam collapse, caused higher deformities rates and DNA damage in the fish embryos than in the control group. Multivariate analysis showed that these sublethal effects may be related to the high levels of metals introduced by mining activities, compromising long-term survival and reproduction success. In addition, it was possible to observe the influence of other sources of pollutants along the river. According to our data, the mathematical model simulated a significant impact on the population density at longer-term exposure, for the sites that showed the most prominent toxicity responses. The fish embryo toxicity test proved to be an effective assay to assess the ecotoxicological effects of the pollutants from a major river contaminated by a mining dam collapse and showed that the survival rate per se was not a suitable endpoint to assess the toxicity of the pollutants. As a consequence, we contributed to shed a light on a potential underestimated impact of pollutants in sediments of the DRB on the native organisms at distinct biological levels of organizations.

Post hatching stages of tropical catfish Rhamdia quelen (Quoy and Gaimard, 1824) are affected by combined toxic metals exposure with risk to population.

Toxic metals and silver nanoparticles (AgNPs) are of great importance as pollutants and their frequent use increases the risk of exposure to biota, but few studies have described co-toxic effects in aquatic organisms. In fish, the method using early stages of development are interesting parameters to validate ecotoxicological studies, and more recently, the use of mathematical models has substantially increased the efficiency of the method. Post hatching stages of native catfish Rhamdia quelen were exposed to single or combined mixtures of toxic metals (Mn, Pb, Hg or AgNPs) in order to study its effects. Fertilized eggs were exposed for 24, 48, 72, and 96 h, where hatching and survival rates, malformation frequency, and neuromast structure damages were evaluated. The results showed alterations in hatching rate after single and combined exposure to metals, but mixtures showed effects more severe comparatively with the single exposures. A similar result including a time-dependent effect was observed in survival rates and incidence of deformities. Overall, embryos and larvae were sensitive to toxic metals exposure while the mathematical modeling suggested a population reduction size including risk of local extinction.

2,4,6-Tribromophenol is toxic to Oreochromis niloticus (Linnaeus, 1758) after trophic and subchronic exposure.

The presence of 2,4,6-Tribromophenol (TBP) in the environment increased the risk of exposure to aquatic organisms affecting the animal development or metabolism. The current study investigated the low, subchronic and trophic effect of TBP in both, male and female adult of Oreochromis niloticus. The fish were exposed to 0.5 or 50 ng g-1 of TBP every ten days for 70 days. Then, hepatosomatic (HSI) and gonadosomatic (GSI) indexes, erythrocyte parameters (hemoglobin content, nuclear morphology and morphometrical abnormalities), biochemical endpoints (glutathione S-Transferase and catalase activities, non-protein thiols, lipid peroxidation and protein carbonylation levels in the liver; and acetylcholinesterase activity in the brain and muscle), histopathological analysis (liver) and vitellogenin levels (plasma) were considered. TBP affected the HSI in male and female fish, but not the GSI. Principal Component Analysis revealed that erythrocytes from males are more sensitive to TBP exposure. Likewise, TBP induced the expression of vitellogenin, CAT activity and liver lesion in male fish comparatively with control group, but GST and NPT were influenced only by sex. Finally, the results showed that the antioxidant mechanism and cholinesterase activity effects were more pronounced in male than in female. The current data shows evidences of estrogenic endocrine disruption and toxicity in O. niloticus exposed to TBP, revealing the risk of exposure to biota.

Effects of trophic 2,2', 4,4'-tetrabromodiphenyl ether (BDE-47) exposure in Oreochromis niloticus: A multiple biomarkers analysis.

Polybrominated diphenyl esters are emerging environmental contaminants with few toxicological data, being a concern for the scientific community. This study evaluated the effects of BDE-47 on the health of Oreochromis niloticus fish. The animals were exposed to three doses of BDE-47 (0, 0.253, 2.53, 25.3 ng g-1) every 10 days, for 80 days. The BDE-47 affected the hepatosomatic and gonadosomatic index in female and the condition factor by intermediate dose in both sexes. The levels of estradiol decreased and the T4 are increased, but the vitellogenin production was not modulated in male individuals. Changes in AChE, GST, LPO and histopathology were observed while the integrated biomarker response index suggests that the lowest dose of BDE-47 compromised the activity of antioxidant enzymes. The oral exposure to BDE-47 in environmental concentrations is toxic to O. niloticus and the use of multiple biomarkers is an attribution in ecotoxicology studies and biomonitoring programs.

Dimethylsulfoxide, methanol and methylglycol in the seminal cryopreservation of Suruvi, Steindachneridion scriptum.

The aim of this study was to analyze the effect of 5%, 7.5%, 10%, 12.5% and 15% dimethylsulfoxide (DMSO), methanol and methylglycol alcohols on the cryopreservation of sperm from Steindachneridion scriptum. Male specimens (n = 15) were obtained from Pisciculture and sperm samples were collected by abdominal massage. Post collection the fresh sperm sample was diluted in the Beltsville Thawing Solution and sperm motility was evaluated. Results indicated that the most precise parameters for total and progressive motility were obtained with the use of methylglycol (all concentrations) and 7.5% and 10% methanol (P < 0.05). The motility of the sperm was sustained for the longest time period when 5%, 7.5% and 15% DMSO was used; similar results were also seen for 5% methanol and methylglycol at 7.5%, 10%, 12.5%, and 15% concentration (P < 0.05). With respect to reactive oxygen species it was observed that the production of ROS decreased only in presence of 5% methylglycol but not when DMSO (5%) was used (P < 0.05). Although the use of methanol (12.5%) allowed for a lesser membrane fluidity as compared to DMSO 12.5% (P < 0.05), membrane functional integrity was greater with 10% and 12.5% DMSO (P < 0.05) as compared to 10% methanol or 5% methylglycol (P > 0.05). Additionally, when major mitochondrial functionalities were assessed it was observed that the values obtained with use of 12.5% and 15% DMSO were comparable to all except 5% methyglycol (P < 0.05). In conclusion, the results of the present study indicate that 7.5% methylglycol was the most effective treatment for the cryopreservation of the S. scriptum sperm.

Embryo toxicity assay in the fish species Rhamdia quelen (Teleostei, Heptaridae) to assess water quality in the Upper Iguaçu basin (Parana, Brazil).

The Iguaçu River is one of the largest and most important rivers in the Southern of Brazil. The Upper Iguaçu Basin is responsible for water supply (80%) of the Metropolitan Region of Curitiba (MRC). After crossing a large urban region, the river is polluted by domestic and industrial sewage, but despite of that few ecotoxicological studies have been performed in order to evaluate the water quality from Iguaçu River. The aim of the present study was to investigate the risk of exposure of Iguaçu water to biota and also human population. In this terms, was utilized the survival effect and the morphological deformities in larval embryos of Rhamdia quelen, a native South America species. The results showed a high level of pollution in all studied sites along the Upper Iguaçu River including PAHs and toxic metals such as lead. The lethal and non-lethal effects described in earlier stages of development suggest an elevated risk to biota. This data was corroborated by the theoretical model, showing that the pollutants present in water from Iguaçu River may further reduce the fish population density including risk of local extinction. The present study reflect the needs to conduct in-depth research to evaluate the real impact of human activities on the endemic fish biota of Iguaçu River including the risk for human populations.