Effects of the herbicide atrazine in neotropical catfish (Rhamdia quelen).

The exposure to a world-wide used herbicide atrazine (ATZ) (96h exposure to 2, 10, and 100µgL(-1)), was investigated on the freshwater fish Rhamdia quelen through a multi biomarker approach. Liver histopathology revealed leukocyte infiltration, hepatocyte vacuolization like steatosis and necrosis areas, leading to raised lesion index levels in all tested concentrations. The increase of free melanomacrophage numbers was observed. Gill filaments revealed considerable loss of the microridges on pavement cells at 10 and 100µgL(-1) of ATZ, and a significantly increased of chloride cell (CC) number and density on apical surface area at 100µgL(-1) of ATZ. CAT, GST, GPx, and GR activities were inhibited by all tested concentrations. GSH levels were reduced in individuals exposed to 100µgL(-1). Osmoregulatory function was also disturbed. We observed an increase of plasma magnesium concentrations at 10µgL(-1). Additionally the inhibition of branchial carbonic anhydrase activity was observed at 100µgL(-1). In the kidney, carbonic anhydrase activity decreased only in the group exposed to 2µgL(-1). These results suggest that ATZ, represents a potential ecotoxicological hazard and can be hepatotoxic and nephrotoxic even low concentrations. The current study was the first to show the nephrotoxic effect of ATZ in fish. Besides, in Brazil, the environmental protection agency (CONAMA) establishes that the maximum allowed level of dissolved ATZ in water is 2µgL(-1), but the present results showed that this concentration may cause histopathological, biochemical and physiological changes in R. quelen.

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.

Ionic regulation in aglomerular tropical estuarine pufferfishes submitted to sea water dilution.

Two common tropical estuarine pufferfishes were used in this study. The main species was Sphoeroides testudineus Linnaeus, 1758, a very abundant species in the estuaries of Paranaguá Bay (Paraná, Brazil), found in waters of salinity between 0 per thousand (tidal creeks) and 34 per thousand (tidal plains). The second species was S. greeleyi Gilbert, 1900, a species limited in distribution to an area of higher salinity ( approximately 30 per thousand) than S. testudineus. The present work thus aimed at evaluating the capacity of ionic regulation of both species of pufferfishes when submitted to salinity decrease, relating the results with both species' distribution in nature. Ion regulation curves for sodium (Na(+)), chloride (Cl(-)), and magnesium (Mg(2+)) ions after 6 h and 15 days of exposure of the abundant S. testudineus to the salinities of 30 per thousand, 20 per thousand, 10 per thousand, and 5 per thousand were elaborated, as well as for Cl(-) and Mg(2+) after 6 h and 15 days of exposure of both species to the extreme salinities of 35 per thousand and 5 per thousand. Both species kept their plasma Cl(-) ( approximately 120-160 mM), and Mg(2+) ( approximately 1.3 mM) concentrations stable, as did S. testudineus for Na(+) ( approximately 130 mM). Na(+) (measured only for S. testudineus) and Cl(-) were either hyper-regulated (in 5 per thousand) or kept iso-ionic ( approximately 7-10 per thousand), but more often hypo-regulated (20-35 per thousand). In contrast, Mg(2+) was strongly hypo-regulated in all salinities. According to their distribution records in nature, S. greeleyi was less able to tolerate strong sea water dilution, showing mortality after 5 days in 5 per thousand water. These estuarine pufferfishes are thus efficient regulators of plasma ionic concentrations in diluted sea water, as expected from their occupation of estuaries. The experiments have supported the distribution records of both species in the estuarine complex and resident estuarine species were thus characterized with respect to their osmoregulatory capacities.