Bioconcentration of Cadmium and Toxic Effects on Life-History Traits of Pond Snails (Lymnaea palustris and Lymnaea stagnalis) in Laboratory Bioassays

Abstract

We studied the bioconcentration and the individual effects of Cd on life-history traits of Lymnaea stagnalis and Lymnaea palustris exposed to increasing Cd concentrations for 4 weeks in controlled conditions. Internal Cd concentrations were linearly correlated to Cd concentrations of exposure in both foot and viscera of L. stagnalis and in the foot of L. palustris, and they were linked by a logistic relationship with environmental contamination in the viscera of L. palustris. If LC₅₀s were higher than the highest Cd concentrations of exposure (L. stagnalis: 160 µg L^–1; L. palustris: 320 µg L^–1), other dose-dependent responses affecting life-history traits were noted in both species. In L. stagnalis, EC₅₀ for growth was evaluated at 142 µg L^–1 and growth inhibition was correlated with internal Cd concentrations by a linear relationship. L. palustris was more sensitive to Cd than L. stagnalis because its EC₅₀-growth was three times lower (58 µg L^–1 after 28 days). Dose-dependent responses were obtained for several parameters of fecundity of L. palustris. EC₅₀ for the mean number of egg masses or mean number of eggs per individual were close to 60 µg L^–1, whereas for the mean number of eggs per egg mass, the EC₅₀ was higher, with a value of 124 µg L^–1. The percentage of hatching versus the total number of eggs was 60% in controls, and no embryos were able to hatch at the lowest tested Cd concentration, 40 µg L^–1. The high sensitivity of fertility was due to Cd blocking embryo development, particularly for the latest embryonic stages just before hatching. The present results constitute useful data to develop laboratory tests using pond snails for freshwater risk assessment.