METAMORPHOSIS OF TWO AMPHIBIAN SPECIES AFTER CHRONIC CADMIUM EXPOSURE IN OUTDOOR AQUATIC MESOCOSMS (original) (raw)
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Critical Period of Sensitivity for Effects of Cadmium on Frog Growth and Development
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Cadmium is a ubiquitous pollutant in aquatic environments that can alter organismal physiology and ecology. Previous experiments found that ecological Cd exposures increased the growth and development of two North American anurans. However, the generality of these effects among species, the time period over which they occur, and the mechanisms responsible remain conjectural. The goal of the present study was to determine the critical period of sensitivity of Rana pipiens exposed to ecologically relevant levels of Cd. We exposed tadpoles to Cd (0 [control], 1.0, and 10.0 g/L) from Gosner stage (GS) 25 to metamorphic climax. We assessed effects of Cd on amphibian length, survival, and development during premetamorphosis (GS 25-30) and prometamorphosis . After 14 d of exposure, we staged tadpoles and recorded snout-vent length. Tadpoles were then pooled according to treatment and stage (GS Յ 29 or GS Ն 30) and allowed to undergo metamorphic development. Tadpoles exposed to 10 g/L were significantly larger and more advanced in development by 14 d. Survival to forelimb emergence exceeded 90% in all treatments, and time to metamorphic climax was not different from that in controls. Body burdens of Cd were positively correlated with increasing treatment. Early amphibian development (premetamorphosis) was shown to be the critical period of sensitivity for growth and development. Whereas the freshwater criterion for Cd appears to be protective for survival, a lack of knowledge remains about the sublethal effects of chronic exposures of metal pollutants, especially as they relate to tissue concentrations at various stages of amphibian life history.
Effects of cadmium exposure on bioaccumulation and larval growth in the frog Rana ridibunda
Environmental Pollution, 1999
The bioaccumulation of cadmium and the eect on growth of larvae of the frog Rana ridibunda after exposure to Cd for 15 and 30 days was investigated. The 96-h LC 50 value was 71.8 ppm. The water content of all the tadpoles exposed to all cadmium concentrations was higher than that of controls. There was a tendency for the animals exposed to Cd to retard their growth. Mortality rates at 15 days exposure increased with increasing cadmium concentration and remained constant in all the cadmium concentrations at 30 days exposure. Cadmium accumulation was higher in the 15 days exposed tadpoles, compared to that of 30 days exposure. Growth retardation may be a factor contributing to the declining of amphibian populations, since they, because of their smaller size, spend more time in more vulnerable stages, becoming thus more susceptible to predators.
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h i g h l i g h t s • Cadmium caused concentration and time dependent mortality in Rana limnocharis tadpoles. • Cadmium reduced the time to metamorphosis in R. limnocharis. • The body weight at metamorphosis decreased while body length increased following cadmium exposure in R. limnocharis. • Cadmium caused chromosome and DNA damage in R. limnocharis.
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2012
The hepatic bioaccumulation of cadmium in Hoplobatrachus occipitalis and Bufo maculatus were assessed for 14 and 28 days respectively. The amphibians were exposed to sub lethal cadmium concentrations of 0.25, 0.50, 1.00 and 2.00 mg/l. Bioaccumulation in H. occipitalis and B. maculatus increased significantly (p<0.05) in both periods of exposures. There was no significant difference in bioaccumulation between the 14 and 28 days exposures. There was also no significant difference in the bioaccumulation of cadmium between two amphibian species. The study suggested that the release of cadmium into the environment could possibly affect the well-being of amphibians as well as resulting in further decline of these very sensitive organisms that contribute significantly to the food web. There is therefore the need to protect amphibians from habitat alteration due to cadmium pollution with a view to sustaining the rich biodiversity in the Nigerian Niger Delta ecological zone.
Acute Toxicity of a Heavy Metal Cadmium to an Anuran, the Indian Skipper Frog Rana cyanophlyctis
Iranian Jornal of Toxicology
Background: There has been increasing awareness throughout the world regarding the remarkable decrease in amphibian population. For such amphibian population decline several causes have been given. Cadmium, a heavy metal is released both from natural sources (leaching of cadmium rich soils) and anthropogenic activities to the aquatic and terrestrial environments. This study evaluated the toxicity of heavy metal cadmium to Indian skipper frog Rana cyanophlyctis. Methods: For the determination of LC 50 values for cadmium, four-day static renewal acute toxicity test was used. Five replicates each containing ten frogs were subjected to each concentration of cadmium chloride (15, 20, 25, 30, 35, 40, 45 and 50 mg/L). At different exposure periods (24, 48, 72 and 96 h), the mortality of the frog was subjected to Probit analysis with the POLO-PC software (LeOra Software) to calculate the LC 50 and 95% confidence level.
In this study, morphometric and gravimetric indices were used to determine the impact of cadmium exposure on a sentinel species. Scaling coefficient, condition factor (CF), hepatosomatic index (HSI), renosomatic index (RSI) and gonadosomatic index (GSI) were compared between rice frogs (Fejervarya limnocharis) exposed to different environmental cadmium levels. The result showed that frogs caught from the contaminated site had significantly higher CF (10.296), RSI (0.413) and female GSI (7.594) than frogs from the contaminated site (7.594, 0.380 and 1.594, respectively). For Scaling Coefficient and HSI, albeit being statistically insignificant, these indices showed a similar trend. On the other hand, the male GSI showed a reverse trend where frogs from contaminated site showed higher values than their counterpart from the reference site. However, the differences were not statistically significant. This research concluded that there is a relationship between cadmium contamination with morphometric and gravimetric indices. Therefore, it is suggested that the use of these data could give an idea on the effect of cadmium exposure on the rice frog.
Environmental Toxicology, 2007
The toxic and genotoxic potential of Cadmium (CdCl 2 ) were evaluated by the micronucleus test (MNT) and comet assay (CA) using amphibian larvae (Xenopus laevis and Pleurodeles waltl). Acute toxicity results showed that Cd is toxic to Xenopus larvae exposed from 2 to 50 mg/L and to Pleurodeles from 5 to 50 mg/L, depending on the nature of the water (reconstituted water containing mineral salts or mineral water MW (Volvic 1 )). The MNT results obtained in MW showed that Cd (2 mg/L) is genotoxic to Xenopus, whereas it was not genotoxic to Pleurodeles at all concentrations tested. The CA established that the genotoxicity of Cd to Xenopus and Pleurodeles larvae depends on the concentration, the exposure times, and the comet parameters (Tail DNA, ETM, OTM, and TL). The CA and MNT results were compared for their ability to detect genotoxic effects, considering the concentrations of Cd applied and the exposure time. The CA showed Cd to be genotoxic from the first day of exposure. In amphibians, the CA appears to be a sensitive and suitable method for detecting genotoxicity such as that caused by Cd. # 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 422-435, 2007.
Biochemical changes in the toad, Bufo maculatus treated with sub lethal concentrations of cadmium
This study evaluates the toxicity of cadmium and its impact on biochemical constituents, like superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and Thiobarbituric acid reactive substances (TBARS) in the liver of Bufo maculatus exposed to sub lethal concentrations of the heavy metal for 28 days. Toads exposed to 0.25, 0.50, 1.00 and 2.00 mg/l Cd showed an elevation (p<0.05) in the specific activity of SOD and CAT relative to controls. The increase could be due to enhanced production of these antioxidants to counteract oxidative stress and lipid peroxidation induced by cadmium. Glutathione (GSH) level showed a decline as the concentration of heavy metal increased at p<0.05 level of significance. Thiobarbituric acid reactive substances (TBARS) increased as concentration of cadmium increased. The increased level of TBARS in the liver of cadmium exposed frogs is an indication of increased membrane lipid peroxidation which could lead to cell damage and may prevent the liver from carrying out its metabolic activities.
TURKISH JOURNAL OF BIOLOGY, 2016
The worldwide decline in amphibian populations has made heavy metal pollution a subject of interest. The aim of this work was to analyze the effect of sublethal doses of cadmium (Cd) on the liver, kidney, and blood of Rhinella arenarum specimens. Serum markers indicative of hepatic injury (gamma glutamyltransferase, alkaline phosphatase, pseudo cholinesterase, and total cholesterol) and markers of renal dysfunction (blood urea nitrogen, serum creatinine, calcium, and glucose) showed variation in animals treated with a 0.5 mg/kg dose compared to controls. Histopathological images revealed alterations in the liver (hepatocyte ballooning and hyperplasia of Kupffer cells) and kidney (renal tubular lumen dilation with tubular necrosis) of animals with abnormal serum markers. The above-mentioned lesions were more evident with the 5 mg/kg dose. With the 0.5 mg/kg dose, hematological values remained normal with the exception of the leukocyte formula. Animals treated with 5 mg/kg showed a significant decrease in both white and red blood cell counts and hematocrit and hemoglobin values. Differential leukocyte counts showed neutrophilia, monocytosis, and lymphopenia. Morphological aberrations were found in white and red blood cells. Results indicated that the evaluation of morphological and functional parameters in kidney, liver, and blood is required in order to monitor amphibian populations exposed to chemical contaminants.