Methylmercury is a potent toxic present in Amazonian fish species due to gold mining activities. In the present work, we investigated the morphological effects of methylmercury in liver and kidney of
...Hoplias malabaricus feeding contaminated prey fish over 70 days. Two groups of nine mature fish (tested and control) were acclimatized for four weeks to laboratory conditions and then the tested group fed prey fish previously contaminated at an additional level of 0.075
μg MeHg
g
−1 at 5-day intervals and over 14 successive intervals whereas control group fed uncontaminated fish.
H. malabaricus specimens were then dissected for chemical and morphological analyses. The low and realistic level of MeHg in the prey fish induced a low increase of total mercury in liver (1.8-fold) and muscle (2.2-fold). The biomagnification factor (Hg in predator/Hg in prey) reached 142 in liver and 21 in muscle and was indicative of a relatively fast contamination of internal organs by dietary exposure. The liver of exposed individuals presented leukocyte infiltration, increased number of melano-macrophage centers, necrotic areas and lesions in Disse's space. Evident disorder and chaos in cytoskeleton organization suggest a strong toxic effect in hepatocytes, such as organelles positioning and movement, vesicles traffic and secretion. Head kidney showed large necrosis areas, increased number of melano-macrophages centers, phagocytic areas, intercellular space among parenquimal cells and atypical cells. Injuries and damages to tissues suggest too slow defense mechanisms to immobilize or eliminate ingested methylmercury, demonstrating that the sensitivity of fish cells to methylmercury exposure is higher than it has been previously described in the literature.
For assessing the impact of chlorinated compounds, such as organochlorine pesticides, polychlorinated biphenyls, chlorotriazines (atrazine, simazine), and chlorinated phenylureas (diuron), on the ...Ponta Grossa lake South of Brazil, ten freshwater trahira fish (
Hoplias malabaricus) were collected in October 2005. The contamination status was evaluated by the energy budget and various histopathological markers. The results showed detectable amounts of persistent organic pollutants (POPs) in the liver and muscle; the bioaccumulation was higher in the liver than in the muscle. The presence of some banned pesticides, such as hexachlorobenzene and dichlorodiphenyltrichloroethane, in the liver suggests an acute exposure to these compounds. Some physiological disturbances and morphological damages found in the liver of
H. malabaricus were associated with chlorinated-compound bioaccumulation. The most important alterations in the liver were lesions such as fibrosis, large necrosis area, leukocyte infiltration, and the absence of melanomacrophages (MM). Individuals containing higher concentrations of pesticides, such as aldrin, alachlor, and dichloroaniline (a metabolite of diuron), showed the nonoccurrence of MM in the liver. These data suggest an immunosuppression in the individuals from Ponta Grossa Lake after exposure to POPs. According to the present data, the POPs found in the studied site are bioavailable, induce severe damages in target organs such as the liver, and can disturb the immune system of the trahira. This is the first study of POPs in the Paraná state, and one among the few studies in the south of Brazil. The present data suggest and motivate further chemical and biomonitoring studies in freshwater ecosystems in the south of Brazil.
The impact of nanoparticles on fish health is still a matter of debate, since nanotechnology is quite recent. In this study, freshwater benthonic juvenile fish Prochilodus lineatus were exposed ...through water to three concentrations of TiO₂ (0.1, 1, and 10 μg l⁻¹) and ZnO (7, 70, and 700 μg l⁻¹) nanoparticles, as well as to a mixture of both (TiO₂ 1 μg l⁻¹ + ZnO 70 μg l⁻¹) for 5 and 30 days. Nanoparticle characterization revealed an increase of aggregate size in the function of concentration, but suspensions were generally stable. Fish mortality was high at subchronic exposure to 70 and 700 μg l⁻¹ of ZnO. Nanoparticle exposure led to decreased acetylcholinesterase activity either in the muscle or in the brain, depending on particle composition (muscle—TiO₂ 10 μg l⁻¹; brain—ZnO 7 and 700 μg l⁻¹), and protein oxidative damage increased in the brain (ZnO 70 μg l⁻¹) and gills (ZnO 70 μg l⁻¹ and mixture) but not in the liver. Exposed fish had more frequent alterations in the liver (necrosis, vascular congestion, leukocyte infiltration, and basophilic foci) and gills (hyperplasia and epithelial damages, e.g., epithelial disorganization and epithelial loss) than the control fish. Thus, predicted concentrations of TiO₂ and ZnO nanoparticles caused detectable effects on P. lineatus that may have important consequences to fish health. But, these effects are much more subtle than those usually reported in the scientific literature for high concentrations or doses of metal nanoparticles.
Iguaçu River is the second most polluted river of Brazil. It receives agrochemicals and contaminants of urban and industrial sources along its course. A multibiomarker approach was employed here to ...evaluate the health of a small characin (
Astyanax
spp.) at two sites along the river, sampled during a dry (autumn) and a rainy (spring) season. Biomarkers were condition factor and somatic indices (gonads and liver); genetic damage (comet assay and micronucleus test); enzyme activities such as hepatic catalase (CAT) and glutathione S-transferase (GST), lipoperoxidation (LPO), branchial and renal carbonic anhydrase (CA), acetylcholinesterase (AChE) in the muscle and the brain, histopathology of the liver and gills, and concentrations of polycyclic aromatic hydrocarbons (PAHs) in bile. There were no consistent differences in biomarker responses between the two study sites. Some biomarkers revealed greater potential impact in the rainy season, when increased amounts of contaminants are washed into the river (combined CAT inhibition and LPO increase, CA upregulation). Other biomarkers, however, revealed potential greater impact in the dry season, when contaminants potentially concentrate (GST induction, AChE inhibition, and liver histopathological alterations). Although of a complex nature, field experiments such as this provide rich data for monitoring protocols and assessment of general risk of exposure to pollutants of river systems.
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 11μgCuL−1) for 96h, 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 11μgCuL−1. Decreased occurrence of free melano-macrophages and increased densities of melano-macrophage centers were noted upon exposure to 11μgCuL−1. Gills showed damages on their secondary lamellae already at 2μgCuL−1; hypertrophy and loss of the microridges of pavement cells at 7 and 11μgL−1, and increased in chloride cell (CC) apical surface area (4.9-fold) and in CC density (1.5-fold) at 11μgCuL−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 11μgCuL−1. Glutathione S-transferase activity (GST) at 7μgCuL−1 and superoxide dismutase activity (SOD) at both 7 and 11μgCuL−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 11μgCuL−1, and plasma chloride reduction at 2μgCuL−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 7μgCuL−1. When these effects are compared to data available in the literature for other freshwater fish, also for 96h 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 4μgCuL−1 used against bacteria to 6000μgCuL−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.
► The susceptibility of the fish Rhamdia quelen to copper was evaluated/ R. quelen was shown to be a relatively sensitive species. ► Exposure to copper induces biochemical, morphological, and physiological effects. ► Concentrations frequently employed in aquaculture are in fact not safe enough.
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.
Copper (Cu) is an essential metal utilized in aquaculture activities for both nutritional and disease control. Conversely, this metal can present a risk of exposure to biota depending on the used ...concentration, but data are still scarce and studies to establish the real risk of copper exposure to fish even in aquaculture activities are welcome. To evaluate a set of environmentally realistic doses of inorganic copper and so the potential risk of exposure to reproduction, Oreochromis niloticus were orally exposed to 0.1, 1.0 or 10.0 mg Cu.kg−1 body weight for 60 days (one dose each 10 days). Parameters regarding sperm quality, including viability, membrane integrity, mitochondrial functionality, apoptosis, lipid peroxidation, protein carbonylation, DNA integrity and motility were considered as signs of reproductive impairment. Additionally, as copper is also described as a pro-oxidant metal, we investigated the oxidative balance in liver (Non-protein reduced thiols concentrations-GSH, superoxide dismutase activity-SOD, lipid peroxidation-LPO, protein carbonylation-PCO and glutathione S-transferase-GST activity). Fishes exposed to copper showed poor sperm quality due to the observed reduced motility and motility period. Induced mitochondrial dysfunction, lipid peroxidation and apoptosis in germ cells, as well as DNA fragmentation confirms the high impairment of Cu to reproduction of O. niloticus exposed to copper in realistic doses. Exposure to the highest dose used in this experiment led to oxidative imbalance in liver, corroborating the deleterious effects of this metal to biological systems. These findings strongly suggest that even under very low Cu doses, or realistic doses as utilized in aquaculture activities, the metal may negatively affect O. niloticus reproduction, probably decreasing the success of aquaculture activities.
•Oreochromis niloticus exposed to copper showed poor sperm quality.•Doses of copper used in aquaculture can led to oxidative imbalance in fish liver.•Indiscriminate use in of copper in fish farming could impair fish reproduction.
Trahira (
Hoplias malabaricus) used to investigate the effects of successive Pb(II) or tributyltin (TBT) dietary doses. After 70 days of acclimation, individuals were exposed to 21
μg Pb
g
−1 or 0.3
...μg TBT
g
−1 (5-day intervals, 14 doses). Two experiments were conducted to investigate the histopathological effects (liver and kidney) and measure the cholinesterase activity (muscle and brain) after Pb(II) or TBT dietary doses. A number of morphological effects were observed in liver, including cytoskeleton disturbance, microautophagy of mitochondria, nuclear damage, and cell death. In kidney, necrosis area, increasing of the neutrophils cell number, changes in melano-macrophage centers, and free macrophages were frequently registered after both Pb(II) and TBT exposures. The cholinesterase activity was inhibited in muscle after 14 doses of Pb(II), but no effects were found in individuals exposed to TBT. In summary, this work is the first to report detailed in vivo toxic effects in tropical fish,
H. malabaricus, after dietary sublethal exposure to Pb(II) and TBT.
Oysters have been largely employed as bioindicators of environmental quality in biomonitoring studies.
Crassostrea rhizophorae was selected to evaluate the health status of three estuarine areas ...impacted by anthropogenic activities along the Brazilian coast, in three estuarine complexes, ranging in latitude from 7 to 25°S. In each estuary three sites were sampled in Winter and in Summer: a site considered as reference, and two sites next to contamination sources. Condition index was similar at all sites and estuaries, with the highest values found for Itamaracá oysters in Summer. Necrosis, hyperplasia, mucocyte hypertrophy and fusion of ordinary filaments were the main histopathological lesions observed. Muscle cholinesterase activity was overall similar, but with a strong seasonal effect. Inhibition or activation of branchial total ATPase and Na,K-ATPase activities at the contaminated sites was observed. The health status of these estuarine areas is quite similar, and the combined use of biomarkers is recommended.
Here, we examined the impact of dichlorodiphenyltrichloroethane (DDT) and monomethyl mercury (MeHg) on the redox milieu and survival of hepatocytes from
Hoplias malabaricus (
traíra). After isolation ...and attachment of cells, we established one control and four treatments: DDT (50
nM of DDT), MeHg I (0.25
μM of MeHg), MeHg II (2.5
μM of MeHg) and DDT
*
MeHg I (combination of 50
nM of DDT and 0.25
μM of MeHg). After four days the exposed hepatocytes presented significantly increased damage in lipids (all treatments), proteins (DDT
*
MeHg I and MeHg II) and reduced cell viability (all treatments). Also the antioxidant enzymes catalase, glucose-6-phosphate dehydrogenase (G6PDH), glutathione reductase and superoxide dismutase were affected. The current data showed that despite of some protective responses, the increased disturbs on membrane lipids and proteins, increased hydrogen peroxide levels, and decreased glutathione concentration and cell viability strongly indicate oxidative stress as the reason of hepatotoxicity due to DDT and MeHg exposure. In addition, DDT and MeHg together had greater effect than alone when G6PDH and glutathione-
S-transferase activities and lipids damage were considered. These findings are indicative of hepatotoxicity occurring at realistic concentrations of DDT and MeHg found in Amazonian fish tissues.
