Ahmed T Sharaf El-Din, Mohamed R Habib, Azza H Mohamed, Gamalat Y Osman, Hanan S Mossalem and Roger P Croll
Posters-Accepted Abstracts: Biol Syst Open Access
Heavy metals are common environmental pollutants to the aquatic organisms. Several aquatic species have been used as biomarkers and bio-monitoring subjects for heavy metal pollution. Behavioral changes are sensitive markers of toxicity. The effects of Cd and Mn on the survival, locomotion, attachment and feeding behaviors of the gastropod snail Biomphalaria alexandrina were determined. The 96-h LC50 for Cd and Mn were 0.38 and 156.57 mg/l, respectively. Snails were exposed to sub-lethal concentrations of each metal plus a control for chronic exposure period (16-20 days) and the survival curves were determined. Locomotion and feeding behaviors of snails exposed to Cd and Mn at acute (96 h exposure) and chronic exposure (24 days exposure) intervals were recorded. The survival curves showed that long term exposure of snails to ascending concentrations of Cd and Mn caused a gradual decrease in the survival rate of B. alexandrina in a dose-dependent manner. Compared to control, a significant decrease was recorded in the feeding and locomotion behaviors of exposed snails. The tendency to feed in B. alexandrina was significantly decreased by acute exposure to Cd and completely blocked by Mn exposure. The feeding rate was 4.8�±0.68 bites/min. in Cd-exposed snails compared to 16.3�±1.7 bites/minute in control. A significant decrease was recorded in the locomotion behavior of exposed snail groups compared to control. The path length of traces was 3351.2�±95.3 mm in control compared to 295.3�±50 and 1610.5�±58.9 mm, respectively for Mn and Cd exposed snails. Thus, sub-lethal metal concentrations affected B. alexandrina behaviors, potentially impacting the snailâ��s activity and tendency to feed. The present study also demonstrated B. alexandrina as a sensitive bio-indicator and can be used as a model organism to assess heavy metals risk factors for severe toxicity in freshwater ecosystems.
