Mesotrione herbicide promotes biochemical changes and DNA damage in two fish species.

Mesotrione is one of the new herbicides that have emerged as an alternative after the ban of atrazine in the European Union. To our knowledge, any work using genetic or biochemical biomarkers was performed in any kind of fish evaluating the toxicity of this compound. The impact of acute (96 h) exposure to environmentally relevant mesotrione concentrations (1.8, 7, 30, 115 e 460 µg L-1) were evaluated on the liver of Oreochorimis niloticus and Geophagus brasiliensis by assessing the activity of superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-S- transferase (GST), the levels of reduced glutathione (GSH), carbonyl assays (PCO) and lipid peroxide (LPO) as well as the DNA damage to erithrocytes, liver and gills through the comet assay. We observed an increase in the concentration of GSH and the GPx activity in O. niloticus, and the GST and SOD activity in G. brasiliensis. We found significant increase in DNA damage in all tissues in both species. The results indicated that the acute exposure to mesotrione can induce oxidative stress and DNA damage in both species.

Risks of waterborne copper exposure to a cultivated freshwater Neotropical catfish (Rhamdia quelen).

As it is the case in all animal food production systems, it is often necessary to treat farmed fish for diseases and parasites. Quite frequently, fish farmers still rely on the aggressive use of copper to control bacterial infections and infestations by ecto-parasites, and to manage the spread of diseases. The susceptibility of the neotropical fish Rhamdia quelen to copper was here evaluated at different waterborne copper concentrations (2, 7 or 11 µg Cu L(-1)) for 96 h, through a multi biomarkers approach. Liver histopathological findings revealed leukocyte infiltration, hepatocyte vacuolization and areas of necrosis, causing raised levels of lesions upon exposure to 7 and 11 µg Cu L(-1). Decreased occurrence of free melano-macrophages and increased densities of melano-macrophage centers were noted upon exposure to 11 µg Cu L(-1). Gills showed damages on their secondary lamellae already at 2 µg Cu L(-1); hypertrophy and loss of the microridges of pavement cells at 7 and 11 µg L(-1), and increased in chloride cell (CC) apical surface area (4.9-fold) and in CC density (1.5-fold) at 11 µg Cu L(-1). In the liver, catalase (CAT), glutathione peroxidase activities (GPx) and glutathione concentration (GSH) remained unchanged, compared to the control group. However, there was inhibition of 7-ethoxyresorufin-O-deethylase (EROD) at all copper concentrations tested. Glutathione reductase activity (GR) was reduced and levels of lipid peroxidation (LPO) were increased at 11 µg Cu L(-1). Glutathione S-transferase activity (GST) at 7 µg Cu L(-1) and superoxide dismutase activity (SOD) at both 7 and 11 µg Cu L(-1) were reduced. However, copper exposure did not alter brain and muscle acetylcholinesterase (AChE) activity. Osmoregulatory function was also disturbed, in agreement with the above-mentioned changes noted in the gills, as detected by plasma osmolality reduction in the group exposed to 11 µg Cu L(-1), and plasma chloride reduction at 2 µg Cu L(-1). These concentrations also, coherently, lead to inhibition of branchial carbonic anhydrase activity. In the kidney, increased carbonic anhydrase activity was measured in the groups exposed to 2 and 7 µg Cu L(-1). When these effects are compared to data available in the literature for other freshwater fish, also for 96 h of exposure, R. quelen appears as a relatively sensitive species. In addition, the concentrations employed here were quite low in comparison to levels used for disease control in real culture practices (ranging from 4 µg Cu L(-1) used against bacteria to 6000 µg Cu L(-1) against fungal infections). We can conclude that the concentrations frequently employed in aquaculture are in fact not safe enough for this species. Such data are essential for the questioning and establishment of new policies to the sector.

Subchronic effects of dipyrone on the fish species Rhamdia quelen.

The use of the non-steroidal anti-inflammatory drugs such as dipyrone is so widespread that this drug and its metabolites have been detected in effluents and surface water. This study aimed to evaluate the potential toxic effects of dipyrone on the aquatic environment, using a native fish species, Rhamdia quelen. Fish were exposed to three concentrations of dipyrone, 0.5, 5 and 50 µg/L, in the water for 15 days, and hematological, biochemical, genetic and morphological biomarkers were evaluated. The glutathione S-transferase activity decreased in the highest concentration in relation to the control group. In addition, hematocrit, red blood cells and thrombocyte counts were decreased in all three exposed groups in relation to the control group. The comet assay showed DNA damage at the lowest concentration of dipyrone and significant kidney damage. Those results suggest that a constant exposure of aquatic organisms to dipyrone presents potential toxic effects.

An assessment of acute biomarker responses in the demersal catfish Cathorops spixii after the Vicuña oil spill in a harbour estuarine area in Southern Brazil.

The Vicuña oil tanker exploded in Paranaguá Bay (South of Brazil), during methanol unloading operations in front of Paranaguá Harbour, on November 15th, 2004, releasing a large amount of bunker oil and methanol. Two weeks after the accident, the acute effects of the Vicuña Oil Spill (VOS) were evaluated in the demersal catfish Cathorops spixii, comparing a contaminated (at the spill site) and a reference site inside the Bay. Data were compared to previous measurements, taken before the accident, in the same species, from the same sites. The physiological biomarkers were the ones that best reflected acute effects of the spill: plasma osmolality, chloride, calcium, magnesium, and potassium. Morphological (liver and gill histopathology) and genetic (piscine micronucleus and DNA strand breaks) biomarkers revealed that damage was already present in fishes from both reference and contaminated sites inside the Bay. Thus, the reference site is not devoid of contamination, as water circulation tends to spread the contaminants released into other areas of the Bay. Acute field surveys of oil spill effects in harbour areas with a long history of contamination should thus be viewed with caution, and whenever possible previous evaluations should be considered for proper appraisal of biomarker sensitivity, especially in mobile bioindicators such as fish.

Morphological and neurotoxicological findings in tropical freshwater fish (Astyanax sp.) after waterborne and acute exposure to water soluble fraction (WSF) of crude oil.

The water-soluble fraction (WSF) of crude oil is a complex highly volatile and toxic mixture of hydrocarbon chains (polyaromatics, heterocyclics), phenols, and heterocyclic compounds containing nitrogen and sulfur. To evaluate the toxic effects of WSF in tropical freshwater teleosts and to develop methodologies that could investigate the toxic mechanisms of WSF in tropical organisms, an acute toxicity experiment was conducted with Astyanax sp. Three dilutions (15%, 33%, and 50%) of WSF obtained from Campos Bay's crude oil (Brazil) were used to study morphological and biochemical responses of the fish. Prior to exposure, the distribution and rate of volatilization of the WSF into each aquarium for the same exposure period was quantified by spectrofluorimetry. Five individuals of Astyvanax sp. were exposed to duplicate WSF of 0, 15, 33, and 50% for each of 12-, 24-, and 96-h exposures for a total of 120 individuals. Liver and gills were sampled from five fish from each treatment and were analyzed by histology, scanning and transmission electron microscopy. A fragment of muscle was also collected from each fish to measure acetylcholinesterase activity. Water analysis showed that only 4 h after dilution, an important loss of hydrocarbons in 33% and 50% of WSF was observed. In addition, 50% of hydrocarbon mass was lost in all tested dilutions after 24 h with significant difference for the 50% WSF at all measured times, demonstrating the high volatility of WSF in freshwater. Damage in the liver and the gills included the presence of necrosis, loss of hepatocytes limit, inflammation areas, cellular proliferation, aneurysms, and disorganization of the second lamellae. The 33% WSF significantly reduced acetylcholinesterase activity in fish. Our study demonstrated that the WSF of crude oil caused damage in organs and tissues of tropical freshwater Astyanax sp. and provided also the basis for a better understanding of the toxic mechanisms of WSF in freshwater fishes.