Marisa Narciso Fernandes

Subchronic exposure to atrazine induces biochemical and histopathological changes in the gills of a Neotropical freshwater fish, Prochilodus lineatus.

The impact of acute (48 h) and subchronic (14 days) exposures to environmentally realistic atrazine concentrations (2, 10 and 25 μg L(-1)) were evaluated on the gills of Prochilodus lineatus by assessing the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST), the levels of reduced glutathione (GSH) and lipid peroxide (LPO) as well as the histopathological damage. Acute and subchronic exposure to atrazine at 2 or 25 μg L(-1) did not change the activities of GST, SOD, CAT or GPx or the concentrations of GSH and LPO; however, subchronic exposure to 10 μg L(-1) increased the activity of GST, SOD and CAT and the LPO level. Histopathological indexes indicated normal gill function with scattered epithelial changes after acute and chronic exposure to 2 or 10 μg L(-1) of atrazine; however, fish chronically exposed to 25 μg L(-1) of atrazine, although had scattered lesions, the severity of lesions resulted in slightly to moderately gill damage. Acute exposure to atrazine decreased the type 3 MCs (containing acid mucosubstances with sulfate esters) in fish exposed to 2 or 10 μg L(-1) and increased the type 4 MCs (containing all types of mucosubstances) in fish exposed to 25 μg L(-1). Chronic exposure to atrazine reduced the type 3 MCs in fish exposed to 10 or 25 μg L(-1). The gills showed a low sensitivity to atrazine after acute exposure. However, the persistence of atrazine in water (subchronic exposure) promoted an increase of LPO levels in the gills and increased the frequency and severity of histopathological changes. The decreased density of type 3 MCs in fish exposed to atrazine suggests a mechanism to wash toxic substances away from the gill surface.

How aluminium exposure promotes osmoregulatory disturbances in the neotropical freshwater fish Prochilus lineatus

The aim of this study was to understand the effects of the interaction between aluminium and low pH in a native fish species Prochilodus lineatus. Thus, juveniles of this neotropical fish species were exposed to 196 microg L(-1) of dissolved aluminium in acid water (Al group), only to acid water (pH group) or to water with neutral pH (CTR group) for 6, 24 and 96 h. Al effects were evaluated with regard to hematological parameters (hemoglobin, hematocrit and red blood cell number), plasma ions and osmolarity, density and distribution of chloride cells (CC), Na(+)/K(+)-ATPase activity in the gills, metabolic (protein and glucose) and endocrine (cortisol) parameters. The fish exposed to Al had increased hematological and metabolic parameters in relation to the CTR group after all periods of exposure. In fish exposed to Al for 24 and 96 h plasma ions and osmolarity were significantly lower and the identification of the enzyme Na(+)/K(+)-ATPase by immunohistochemistry indicated a reduction in the number of CC in the gills. Enzyme activity was 50% lower in fish exposed to Al in all experimental times. Taken together these results showed that acute exposure to Al causes an ionic unbalance, probably related to the effects of Al on Na(+)/K(+)-ATPase activity, on the distribution and number of chloride cells in the gills as well as the effects associated with the stress response caused by the presence of the metal.

Acute exposure of a glyphosate-based herbicide affects the gills and liver of the Neotropical fish, Piaractus mesopotamicus

The aim of this study was to determine the acute toxicity of Roundup(®) Ready (RR) in Piaractus mesopotamicus, and evaluate the effects on the morphology of the gills and liver of exposed surviving fish. Fish were exposed to 3.0, 3.5, 4.0 and 4.5mgL(-1) of glyphosate, and the LC(50);48h was estimated at 3.74±0.2mgL(-1). Gill histopathology was rare, and the activity of Na(+)/K(+)-ATPase enzyme did not change, suggesting normal function. However, the damage to the liver was classified as moderate to severe. Cytoplasmic vacuolization, lipid accumulation, nuclear and cellular membrane alterations and glycogen depletion were found in the liver, suggesting a reduction in the liver function. The glyphosate in the RR formulation was classified as moderately toxic for P. mesopotamicus, and the severe damage in the liver may affect the detoxification and/or tissue repair process and contribute to fish death.

Relationships between oxygen availability and metabolic cost of breathing in Nile tilapia (Oreochromis niloticus): aquacultural consequences

Oxygen uptake (Vo2) and ventilatory parameters were measured during graded hypoxia in Nile tilapia (Oreochromis niloticus) previously acclimated to normoxia (Po2 ≥ 125 mmHg; 90% sat.) at 25 ± 1°C. Vo2 was slightly increased as the oxygen tensions of inspired water (Pio2) were reduced. Gill ventilation (VG) increased significantly in response to hypoxia and resulted mainly in larger breath volume (VS,R) whereas breathing frequency was hardly changed. The increase in VG was also accompanied by a reduction in oxygen extraction efficiency (Eo2-%). The metabolic cost of VG was calculated as 3% of total Vo2 in normoxia but increased to 18% during severe hypoxia (Pio2 = 30 mmHg; 21% sat.). The results suggest that this species should not be exposed to long periods of low O2 since portions of the metabolic energy are used by the ventilatory system to maintain O2 uptake to the detriment of other metabolic functions such as weight gain and growth.

Hematological and biochemical alterations in the fish Prochilodus lineatus caused by the herbicide clomazone

The indiscriminate use of herbicides has led to the contamination of water bodies, possibly affecting the health of aquatic biota. Therefore, to evaluate the possible effects of the clomazone-based herbicide (Gamit(®) 500) on the fish Prochilodus lineatus, juveniles were exposed for 96h to three concentrations (1, 5 and 10mgL(-1)) of clomazone, and an analysis was made of their hematological parameters: hemoglobin (Hb); hematocrit (Hct); red blood cell (RBC) count; mean corpuscular volume (MCV); mean corpuscular hemoglobin (MCH); mean corpuscular hemoglobin concentration (MCHC) and biochemical parameters: glutathione S-transferase (GST); catalase (CAT); glutathione peroxidase (GPx) and acetylcholinesterase (AChE). Hct presented a significant decrease at the concentration of 10mgL(-1), while the parameters Hb, HCM and MCHC presented a significant decrease at the two higher concentrations, indicating an anemic condition. The RBC increased significantly at the lowest concentration, possibly due to the release of new red blood cells into the bloodstream in response to splenic contraction, which may occur as an adaptive response to the stressor agent. P. lineatus presented activation of the biotransformation pathway, indicated by augmented hepatic activity of the enzyme GST and hepatic activation of the antioxidant enzyme CAT at the higher concentrations. Liver GPx was significantly inhibited at the higher concentrations, which may indicate the efficient action of CAT in the elimination of H2O2 or its competition with GST for the same substrate (GSH). AChE activity in brain and muscle was inhibited at the higher concentrations, indicating the neurotoxic effects of the herbicide in the fish. The hematological and biochemical alterations led to the conclusion that the herbicide clomazone has toxic effects on the species P. lineatus, and that its presence in the environment may jeopardize the health of these animals.

Biomarker responses as indication of contaminant effects in Oreochromis niloticus.

The current study investigated oxidative stress parameters (enzymes activities, metallothionein content and lipid peroxidation) in freshwater fish, Oreochromis niloticus, tilapia exposure to Monjolinho River (in 4 months of year: January, April, July and November). One critical site in Monjolinho River (site B) was assessed in comparison to a reference site (site A). Water pH and oxygen concentration was lower than that recommended by CONAMA (Brazilian National Environmental Committee), resolution 357/2005 for protection of aquatic communities, and ammonium and the metals Cu, Zn, Mn and Fe (on all months) concentrations were higher than the maximum concentration recommended. Glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities were significantly decreased in liver and muscle in tilapia from Monjolinho River, throughout the year, in relation to reference except in gills that SOD activity increased. Glutathione S-transferase (GST) activity was significantly increased in liver of the tilapia from Monjolinho River in all sites, in relation to reference except in gills that GST activity increased in July and decreased in November, suggesting that GST activity could be induced to neutralize the pollutants toxicity. On the other hand, GST activity was significantly decreased in white muscle indicating a toxic effect of pollutants, resulting in a decreased ability of tilapia to perform defense reactions associated to GSTs. The decrease of catalase (CAT) activity in gills of the O. niloticus together with the increase of SOD activity, could explain the increased lipid peroxidation (LPO) level in this organ. Metallothionein levels in liver and gills were significantly high in all sites. Results indicate that the exposure to metals caused severe damage to tissues; despite the consensually assumed antioxidant induction as a sign of exposure to contaminants the effects seem in part to be mediated by suppression of antioxidant system with SOD, CAT and GPx as potential candidates for tissues toxicity biomarkers of pollutants.

Cardio-respiratory responses in two ecologically distinct erythrinids (Hoplias malabaricus and Hoplias lacerdae) exposed to graded environmental hypoxia

SynopsisEcologically distinct species of Hoplias were studied as to the cardio-respiratory responses to graded hypoxia. Hoplias malabaricus maintained a constant oxygen uptake down to a PiO2 of 20 mmHg. Oxygen uptake declined markedly at lower PiO2 and, concomitantly, cardiac frequency decreased. Concurrent reductions of oxygen uptake and heart rate also occurred in Hoplias lacerdae but at the considerably higher PiO2 of 35 mmHg. These species-specific differences are consistent with the respective habitats: H. malabaricus occurs in stagnant hypoxic water, whereas H. lacerdae inhabits well-oxygenated rivers.

Effects of atrazine on the gill cells and ionic balance in a neotropical fish, Prochilodus lineatus.

The effects of the herbicide atrazine on the gill of the freshwater fish Prochilodus lineatus were evaluated after exposure of fish to 2, 10 and 25 μg L(-1) atrazine during 48 h (acute exposure) and 14 d (subchronic exposure). Ions and osmolality were measured in plasma and gill samples were taken to determine the Na(+)/K(+)-ATPase (NKA) and carbonic anhydrase (CA) activities and for morphological analysis. Plasma osmolality and Na(+) and Cl(-) ions changed depending on atrazine concentration, but atrazine exposure had no effect on the Na(+)/Cl(-) ratio. NKA activity did not change after atrazine exposure, but CA activity decreased in fish exposed to 25 μg L(-1) for 14 d. Gill MRC density decreased after acute exposure but did not change in fish exposed to the subchronic treatment. The MRC density at the epithelial surface increased in fish exposed to 25 μg L(-1), and the MRC fractional area (MRCFA) increased in fish exposed to 10 μg L(-1). The changes in MRCs provide evidence of morphological adjustments to maintain ionic homeostasis in spite of the inhibition of CA activity at the highest atrazine concentration.

Morphometric comparison of the respiratory organs in the South American lungfish Lepidosiren paradoxa (Dipnoi).

In light of the relationship of lungfish to the origin of tetrapods, information on the respiratory biology of lungfish can give insight into the functional morphological and physiological prerequisites for the conquest of land by the first tetrapods. Stereological methods were employed in order to determine the respiratory surface area and thickness of the water‐blood barrier or air‐blood of the gills, lungs, and skin, respectively, of the South American lungfish Lepidosiren paradoxa. The morphometric diffusing capacity was then determined by multiplying by the appropriate Krogh diffusion constants (K). Our results indicate a total diffusing capacity of all respiratory organs of 0.11 mL min−1 mmHg−1 kg−1, which is more than twice the value of the physiological diffusion capacity (approximately 0.04 mL min−1 mmHg−1 kg−1). Of this, 99.15% lies in the lungs, 0.85% in the skin, and only 0.0013% in the gills. Since K for CO2 is 20–25 times greater than for O2, diffusing capacity of CO2 through the skin is potentially important. That of the gills, however, is negligible, raising the question as to their function. Our results indicate that the morphological prerequisites for terrestrial survival with regard to supporting aerobic metabolism already existed in the lungfish.

Susceptibility of the Amazonian fish, Colossoma macropomum (Serrasalminae), to short-term exposure to nitrite

Abstract Nitrite (NO 2 − ) is toxic to fish. High levels of NO 2 − may develop in natural aquatic environments or in aquaculture systems, a situation that is aggravated in tropical regions by high temperatures and low dissolved oxygen. The toxicity of NO 2 − was evaluated in the Amazonian fish, Colossoma macropomum to define the environmental quality standards and management of culture system for this species. The acute toxicity of NO 2 − was tested using a renewal bioassay system and a series of increasing NO 2 − concentrations up to 0.4 mM NO 2 − (5.6 mg l −1 ). Blood samples were taken after a 96-h exposure to NO 2 − to determine the hematological parameters, methaemoglobin (MetHb) concentration and plasma nitrite bioaccumulation. The 96-h LC 50 was calculated as 0.13±0.06 mM NO 2 − (1.82±0.98 mg l −1 ), indicating high sensitivity of this species to nitrite. Nitrite bioaccumulation resulted in methaemoglobinemia (66–76%) and hemolytic anemia (depression in total hemoglobin (Hb) concentration, hematocrit (Ht) and red blood cells (RBC)), which compromise the transport of O 2 through the blood from the gills to the tissues. The increase of mean corpuscular Hb concentration in fish exposed to 0.04 and 0.2 mM NO 2 − suggested changes in the ionic transport across the erythrocyte membrane. The absence of ecomorphological responses such as lip formation and aquatic surface respiration (ASR) during NO 2 − exposure indicates that the mechanism involved in nitrite-induced hypoxia differs from that induced by environmental hypoxia. These findings reveal that intensive aquaculture systems of C. macropomum should be managed so as to avoid even low levels of NO 2 − , since the effects of nitrite may compromise the fishs performance in an environment in which high temperature and daily fluctuations in dissolved oxygen may aggravate nitrite intoxication.