Physella acuta growth in response to varying concentrations of Zinc

Abstract

Bladder snails, Physella acuta, are well-known for their fast maturation and reproduction as well as having higher tolerance to heavy-metal polluted stream. We investigated the effects of heavy metals, specifically zinc, on the growth of P. acuta by exposing them to 3 different zinc concentrations (200, 400, and 800 μg/L) and a negative control (0 μg/L) for 20 days. We quantified the shell length (SL) and body mass (BM) growth rate of P. acuta as a proxy of the effect of zinc concentrations. The 800 μg/L zinc treatment yielded both the highest mean growth rate of SL (0.0466±0.0013 cm/day) and BM (0.095±0.007 g/day). A general trend of increasing SL and BM growth rates of P. acuta was observed with increasing zinc concentrations. Statistical tests proved significance in variation in both BM (p=.001) and SL (p=.015) growth rates, while only 800μg/L treatment against the control showed significance on SL and BM growth rates (p=.001, p=.01). Furthermore, survival rates varied between the highest 76.7% in control and the lowest 28% in 800 μg/L treatment. The cause of mortality and therefore varying survival rates are not specified with possibilities including but not limited to; acclimation, overfeeding, and handling. Any egg masses observed were recorded by count and size (small, medium, large). Overall, the varying concentrations of zinc in this experiment did not negatively impact P. acuta as they were still able to thrive, reproduce with viable egg masses, and adapt to the varying levels of Zinc.