Cadmium-induced genotoxicity in zebrafish at environmentally relevant doses.

Genotoxic effects of cadmium on zebra fish Danio rerio have been assessed by random amplified polymorphic DNA and real time PCR, followed by a comparison of the melting temperature patterns between each amplification reaction. Fish were exposed to two concentrations of cadmium chloride dissolved in the medium (1.9+/-0.6 microg Cdl(-1), C(1); 9.6+/-2.9 microg Cdl(-1), C(2)) for 21 days. A discriminative RAPD probe, OPB11, was first selected producing differential band patterns between control and metal-exposed genomic DNAs. RAPD-PCR showed an increase in the relative hybridization efficiency of OPB11 on the genomic DNAs coming from fish exposed to both Cd concentrations as compared to the control condition. In addition, the RAPD-PCR melting temperature patterns showed that with the OPB11 probe, the frequency of PCR products whose fusion temperature belongs to the [86-87 degrees C] interval decreased with Cd contamination, whereas an increase of frequency for the [78-80 degrees C] and [85-86 degrees C] intervals was correlated with Cd exposure.

Cadmium uptake by the European eel: trophic transfer in field and experimental investigations.

Due to its status of threatened species and being heavily contaminated by metals, the European eel (Anguilla anguilla) was selected to investigate cadmium contamination levels of fish settled along a historically cadmium-contaminated hydrosystem, the Garonne-Gironde continuum (France), according to its various location sites and fish length. Results have shown an important site effect on cadmium concentrations in liver but not in gills, highlighting the possible predominance of the trophic exposure route. Subsequently, uncontaminated eels were experimentally exposed to cadmium by water uptake and/or trophic route(s). Eels were fed with different preys: white shrimps collected in an unpolluted area in the Gironde estuary, and cadmium-enriched shrimps. Data obtained tend to show that the use of cadmium-enriched food during experimental investigations triggers an underestimation of the metal trophic transfer rate. These two complementary approaches provide some elements to suggest that the trophic route plays an important role in cadmium contamination of wild eels.

Estimation of potential and limits of bivalve closure response to detect contaminants: application to cadmium.

Bivalve closure responses to detect contaminants have often been studied in ecotoxicology as an aquatic pollution biosensor. We present a new laboratory procedure to estimate its potential and limits for various contaminants and animal susceptible to stress. The study was performed in the Asiatic clam Corbicula fluminea and applied to cadmium. To take into account the rate of spontaneous closures, we integrated stress problems associated with fixation by a valve in common apparatus and the spontaneous rhythm associated with circadian activity to focus on conditions with the lowest probability of spontaneous closing. Moreover, we developed an original system by impedance valvometry, using light-weight impedance electrodes, to study free-ranging animals in low-stress conditions and a new analytical approach to describe valve closure behavior as a function of response time and concentration of contaminant. In C. fluminea, we show that cadmium concentrations above 50 microg/L can be detected within less than 1 h, concentrations down to 16 microg/L require 5 h of integration time, and values lower than 16 microg/L cannot be distinguished from background noise. Our procedure improved by a factor of six the cadmium sensitivity threshold reported in the literature. Problems of field applications are discussed.