Natalia Alejandra Ossana

Short communication: Cadmium bioconcentration and genotoxicity in the common carp (Cyprinus carpio)

Heavy metals in the aquatic environment pose high ecotoxicological risk to fish. Cadmium is one of the most abundant pollutants in freshwater bodies in Argentina. An evaluation was performed of the responses of several exposure biomarkers of juvenile Cyprinus carpio exposed during five days to sublethal cadmium (0.5 mgL−1) and cyclophosphamide (5 mgL−1). The assessment involved evaluating the impact of exposures on the following parameters of fish: Condition Factor (CF), Hepatosomatic Index (HSI), tissue accumulation (brain, muscle, gills, liver and blood) and erythrocyte micronuclei (MN) frequency. Compared with controls CF showed no significant changes and HSI registered a declining tendency. The metal accumulated mainly in the gills and to a lesser proportion in the liver and blood; in the brain and muscles, the quantities determined were no different from those found in the controls. MN frequency in erythrocytes increased significantly among fish exposed both to cadmium and to cyclophosphamide.

Effects of sublethal waterborne cadmium on gills in three teleosteans species: scanning electron microscope study

The effects of acute exposure for 96 h to a sublethal concentration of cadmium (300 µg L−1) on the surface gill morphology of the teleosteans Cyprinus carpio, Australoheros facetum and Astyanax fasciatus were studied using Scanning Electron Microscopy (SEM). The main cadmium-induced gill damages in the three species were: structural alterations, oedema and fusion of adjacent secondary lamellae; there was a remarkable disruption of the gill epithelium in Australoheros facetum and excretion of large amount of mucus on the lamellae in Astyanax fasciatus. The reversibility of the alterations after a depuration period was also investigated; in all cases the fishes exhibited a considerable recovery of the gill structure after 96 h in a cadmium-free medium.

Multibiomarker response in ten spotted live-bearer fish Cnesterodon decemmaculatus (Jenyns, 1842) exposed to Reconquista river water

The aim of this paper is to assess the water quality to chemical pollution at Roggero Dam, the headwater of the Reconquista river, and to perform a Cadmium (Cd) contamination pulse simulation through a wide battery of biomarkers which included: genotoxicity and enzymatic biomarker parameters on a neotropical teleost fish namely Cnesterodon decemmaculatus. Water samples were taken in order to determine the rivers physicochemical profile. An integrative approach was applied using a biomarker index. The bioassay involved the use of laboratory culture adult animals, acclimatized in moderately hard water (MHW) and fed ad libitum. A semi-static 96h bioassay was conducted and the experimental groups were as follows: [1] river water (Rg); [2] river water + 2mg/L Cd (RgCd); [3] MHW + 2mg/L Cadmium (Cd), positive metal control; [4] MHW + 5mg/L Cyclophosphamide (positive genotoxicity control -CP); [5] MWH, negative control (NC). At the end of the exposure time fishes were sectioned and the following biomarkers were determined: 1) condition factor rate (CF); 2) for the anterior section (A) (head): glutathione (GSH) and protein (Pr) content; 3) for the body midsection (M) (viscera): Pr, GSH, Glutathione-S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD). Blood samples were also taken from the fish specimens to estimate the frequency of micronuclei (MN) as well as other nuclear abnormalities (NA). The physicochemical profile of the river water sample indicated high Copper concentrations. CAT and SOD activity and total Pr content did not show any significant changes. GST activity decreased in fish exposed to Rg, while GSH content decreased significantly for all treatments compared to controls in MHW. These results would seem to point to a reduction in cell defense capability as a result of the depletion antioxidants such as GSH. The NA frequency increased significantly in all treated groups while MN frequency was increased only in Cd and CP groups. Using some the biomarkers measured, a biomarker index was estimated which revealed that fish exposed to Rg were 90% affected or highly affected, while those exposed to RgCd were 80% and Cd 68% affected or highly affected. The obtained results indicate the usefulness of the use of a battery of variables by means of the biomarker index to analyze water quality.

Do Lithobates catesbeianus tadpoles acclimatise to sub-lethal copper?

The aim of this work was to study the acute effects of short-term exposure (96 hours) to sub-lethal concentrations of copper (2 and 3 mg L−1) on ecotoxicological stress biomarkers in the aquatic stages of Lithobates catesbeianus (syn. Rana catesbeiana) larvae. To this end, the effects of copper on brain acetylcholinesterase, liver and gill catalase and glutathione-S-transferase activities were examined. In addition, the changes in gill structure were monitored by scanning electron microscopy. Neither the survival nor the activity of the biomarker enzymes was affected by copper; however, the gills were affected, exhibiting alterations in the epithelial cells of the tufts. The results were interpreted as evidence that, at the concentrations assayed, there may be an acclimation of the tadpoles to copper; the anomalies observed in the epithelium of the gills may be compatible with the survival of the animals since at their developmental stage the skin plays an important role in the respiratory function.

Cadmium effects on some energy metabolism variables in Cnesterodon decemmaculatus adults

This work is focused on the responses of some energy metabolism variables in Cnesterodon decemmaculatus adults exposed to cadmium under controlled laboratory conditions. This species has been used as bioindicator for evaluating the effects of different chemicals on diverse biological processes and is frequently used as test organism in ecotoxicity studies that include cadmium as reference toxicant. Animals were exposed for 12 days to the following concentrations: 0, 0.45, and 0.8 mg Cd/L. Food intake, fecal production, specific assimilation, condition factor, mortality percentage, oxygen consumption, oxygen extraction efficiency, specific metabolic rate, ammonia excretion, and ammonia quotient were measured. The overall balance was expressed as scope for growth (SFG). Cadmium-exposed groups showed a significant decrease in food assimilation and condition factor at the end of the exposure. There was an increase in specific metabolic rate and a decrease in SFG in the group exposed to 0.8 mg Cd/L. The condition factor and the SFG appeared as sensitive biomarkers of health status and growth of the animals, respectively. Cadmium-exposed fish reduced food intake, which was reflected in a decreased assimilation with concomitant decline in the external energy supply from feeding. Our results highlight the importance of considering the metabolic status of the test organisms when analyzing the responses of the biomarkers usually used as effect parameters in ecotoxicological evaluations under experimental conditions.

Use of integrated biomarker indexes for assessing the impact of receiving waters on a native neotropical teleost fish

In the field of aquatic ecotoxicology, indexes obtained from a battery of biomarkers have proved to be a useful tool for assessing quantifiable and integrated health responses of organisms exposed to pollutants. The objective of this work was to evaluate the effects of exposure to the Reconquista River water (RR) on adults of Cnesterodon decemmaculatus using different integrated indexes. We conducted a 12-d laboratory assay involving the exposure of fish to RR, a negative control (moderately hard water - MHW medium), and a positive control (for genotoxicity with MHW + Cyclophosphamide, CP). There were measured metabolic (food intake and specific assimilation, specific metabolic rate, oxygen extraction efficiency, ammonia excretion, and ammonia quotient), genotoxic (comet assay, micronucleus test, and nuclear abnormalities), morphological variables (total length, body and liver weight) and biochemical variables (Electron Transport System - ETS, Acetylcholinesterase activity - AChE, Catalase - CAT, Glutathione-S-transferase - GST, Glutathione content - GSH and tissue proteins). These variables were grouped into different indexes: morphological (Condition Factor - K and Liver Somatic Index-LSI), metabolic (Scope for Growth-SFG), genetic damage (GDI) and integrated biomarker response - IBR (AChE brain, CAT, GST and GSH liver, GSH gills, ETS muscle) indexes. Results indicated that RR water induced metabolic, biochemical and genetic damages. The SFG, GDI and IBR were suitable to assess the effects of exposure to an environmental sample in an integrated approach, reducing uncertainty due to inherent biomarker variability. These indexes have emerged as promising tools for environmental monitoring studies.

Water pollution monitoring of the Lujan River (Argentina): chemical analyses and hepatic biomarkers in Lithobates catesbeianus tadpoles

The toxicological water quality of the Lujan River (Argentina) was monitored during one year seasonal samplings. Water samples were collected at two points and their toxicological profiles were compared: S1 (reference site), located downstream of a major city and S2, located further downstream, beyond a joint urban sewage and industrial discharge point. A number of abiotic parameters were determined and three water quality indices (WQIs) calculated on the samples. Laboratory toxicity bioassays were conducted exposing Lithobates catesbeianus larvae to samples; a third group of animals were exposed to tap water (controls). Hepatic biomarkers were determined: catalase (CAT), glutathione-S-transferase (GST) and superoxide dismutase (SOD) activities, lipid peroxidation (LPO) and GSH content; CF and HSI were calculated. The scores of the WQIs corresponded to a high pollution condition at both sampling points. ANOVA showed significant differences between sampling sites and controls mainly in CAT activity, GSH content and GST in autumn.

Assessment of physiological effects of sublethal cadmium on Cyprinus carpio

The effects of sublethal and short-term exposure to Cd were assessed with the purpose of studying the energy metabolism parameters in young Cyprinus carpio under laboratory conditions. The fish were exposed to Cd solutions (0.20 mg Cd. L-1) over a two-week term. The assayed concentration was environmentally realistic since it was frequently found in most highly polluted peri-urban water bodies in Argentina. No mortality was recorded among the animals during the experiments. The relationships between assimilation efficiency (U), oxygen consumption as a measure of specific metabolic rate (SMR) and ammonium excretion (AE) were determined. After exposure to Cd, a significant correlation was found between SMR and AE. It was concluded that under the assayed conditions the metal caused alterations in energy-related homeostasis of fish. Most of the responses may be interpreted as indicative of adaptations to compensate for increased energy requirements due to the physiological impairments caused by Cd.