Effects of CaCl sub(2) and CaBr sub(2) on the Fecundity of Planorbarius corneus L

The effects of calcium chloride and calcium bromide, which are used as completion fluids in oil-well bores, on the fecundity of the snail Planorbarius corneus were examined. The snail is one of the most common and indigenous species along the northwestern coast of Croatia where most gas and oil exploration activities are located. During exposure to the chemicals, the egg-masses attached to glass and lettuce leaves were counted and removed weekly. Results showed that the reduction of the mean weekly number of egg-masses increased with increases in the concentrations of the tested solution. Highest negative correlation between the chemicals and the number of egg-masses was found for the mixture of the two chemicals.