2,4-Dichlorophenoxyacetic acid alters intracellular pH and ion transport in the outer mantle epithelium of the bivalve Anodonta cygnea

Tolerance of native and invasive bivalves under herbicide and metal contamination: an ex vivo approach

The literature indicates that exotic species have a greater tolerance to environmental stressors compared with native species. In recent decades, the introduction of contaminants into the environment has increased as a result of industrialization. The objective of this study was to verify the resistance of bivalve mollusks from freshwater native (Anodontites trapesialis) and exotic (Limnoperna fortunei) species to chemical contamination using an ex vivo/in vitro approach. Gill and muscle tissues were exposed to two different types of environmental stressors, copper (metal), and Roundup Transorb® (herbicide). The tissues were submitted to a cytotoxicity test in which the lysosomal integrity was assessed, from the adaptation of a method to isolated cells, and multixenobiotic resistance (MXR) test which evaluated cellular defense. In the exotic species, only copper at 9000 μg/L and Roundup Transorb® at 5000 μg/L were cytotoxic. In the native species, copper cytotoxicity at 900 and 9000 μg/L and Roundup Transorb® at 50 and 5000 μg/L were observed. Results were the same in both tissues. The MXR, responsible for the extrusion of contaminants (cell defense), was inhibited in both species when exposed to the contaminants, this cell defense system seems to be more inhibited in the native species, when exposed to both pollutants, indicating greater sensitivity. Therefore, cytotoxicity may be related to the lack of capacity of cellular defense. In relation to lysosomal integrity, the native species was more sensitive to cytotoxic pollutants, where a greater number of experimental conditions of metals and herbicide showed cytotoxicity, as well as more experimental situations inhibited its ability to defend itself.

The toxicity, bioaccumulation, elimination, conversion of the enantiomers of fipronil in Anodonta woodiana

The enantioselective bioaccumulation and elimination of fipronil in Anodonta woodiana (A. woodiana) were studied and the main metabolites fipronil desulfinyl, fipronil sulfide and fipronil sulfone were determined. The acute toxicity of the enantiomers of fipronil and the three metabolites were also investigated. In the bioaccumulation process, fipronil in A. woodiana reached equilibrium after 11days with BCF value of 0.2, and the enantiomeric fraction (EF) values showed that the bioaccumulation was enantioselective with enantioenrichment of S-fipronil. The degradation of fipronil in A. woodiana fitted first-order kinetics model with half-lives of the enantiomers were 5.8 d for R-fipronil and 7.6 d for S-fipronil, and the EF values decreasing from 0.5 gradually indicating the R-enantiomer was preferentially degraded. The degradation of single enantiomers was also performed and the results revealed a fast conversion of R-fipronil to S-fipronil by A. woodiana. The three metabolites were all detected in A. woodiana-water system, in which fipronil sulfone and fipronil sulfide had higher concentration levels. According to the 72-h LC50 values, S-fipronil was much more toxic than the racemate and R-fipronil. Moreover, the metabolites were more toxic than the parent fipronil. The results suggested the individual enantiomers of chiral pollutants and the metabolites should be considered in the risk assessments.