Using electrotopological state indices to model the depuration rates of polychlorinated biphenyls in mussels of Elliptio complanata

A quantitative structure-activity relationship （QSAR） model on depuration rate constants （ka） of polychlorinated biphenyls （PCBs） in freshwater mussel Elliptio complanata was successfully constructed using electrotopological state indices （ESI） and partial least squares （PLS） regression. The cross validated 2 Qcum and the correlation coefficient R for the model were determined to be 0.845 and 0.954, respectively. The satisfactory Q2cum and R values indicated significantly high robustness and good predictive ability for the model. The model was tested and found acceptable for the prediction of logkd （the logarithm of the deputation rate constants） by validation set. According to the model, an increase in the values of Saasc, S5＇, S4, S5 and S4＇, led to increased logkd, and a decrease in the values of Na, S2, and S6 also resulted in increased logkd. Among these descriptors, Ncl, S aasC, S5＇,, S4 and S5 made significant contributions to the value of logkd. These significant descriptors showed that the depuration of PCBs in Elliptio complanata may be mainly attributed to an equilibrium partitioning process among compartments with different lipid contents, while the reactivity of PCBs with enzymes or other molecules may play a subordinate role.

Effects of a municipal effluent on the freshwater mussel Elliptio complanata following challenge with Vibrio anguillarum

The purpose of this study was to examine the cumulative effects of exposure to a pathogenic bacteria and municipal effluent in the freshwater mussel Elliptio complanata. Mussels were exposed to increasing concentrations of an ozone-treated effluent at 15°C for 7 days. A sub-group of mussels was inoculated with Vibrio anguillarum and exposed to the same conditions as above.After the exposure period, mussels were collected to assess hemocyte count and viability,immunocompetence（phagocytosis and nitrite production）, oxidative stress/inflammation（cyclooxygenase and lipid peroxidation） and oxygen radical/xenobiotic scavenging activity（metallothioniens, glutathione S-transferase）. The results showed that mussels exposed to municipal effluent had increased hemocyte counts, phagocytosis, nitrites, lipid peroxidation and metallothioneins. In the inoculated mussels, the same responses were observed, in addition to cyclooxygenase and glutathione S-transferase activities. Multivariate analyses revealed that（1）the response pattern changed with effluent concentration, where increased responses observed at low effluent concentrations（〉10%, V/V） were attenuated at higher effluent concentrations,（2）the effluent produced more pronounced changes in lipid peroxidation, metallothionein and hemocyte viability, and（3） the simultaneous presence of V. anguillarum led to more important changes in hemocyte count and viability and nitrite levels. In conclusion, the presence of V.anguillarum could alter the response of mussels to municipal effluent, which could lead to increased inflammation in mussels.