No abstract

This study presents the results of observation on growth and reproduction of Planorbarius corneus (Linnaeus, 1758) (Gastropoda, Pulmonata) over the course of several years of continuous rearing in the laboratory in order to use them as test organisms for toxicity testing of chemicals. Some growth and reproduction features (shell diameter increase, fecundity, hatching time and rate, age at first reproduction, juvenile survival), which could provide more information for culturing P. corneus in the laboratory, are presented. The quantitative results of growth and reproduction in laboratory conditions were obtained: heterogenous growth varied between 0.1 mm and 5.3 mm in individual snails, production of 0.6 egg masses per snail/day and 11 eggs per snail/day. A statistically significant negative correlation between initial snail size and growth was noticed. In the second part of the experiment, the reproductive output of 4 isolated snails was compared to that of permanently grouped snails. As a result, 2-fold decreased growth and 4-fold decreased reproductive output in the progeny of isolated animals was noticed.

Concentrated CaCl 2 and CaBr 2 salt solutions of densities up to 2.3 kg L -1 are regularly used to control hydrostatic pressure in oil wells during special operations in the exploration and production of natural gas and crude oil. Various concentrations of high density salts are frequently left in mud pits near the drilling site as waste, polluting fresh and ground waters by spillage and drainage. The toxic effects of these salts have already been observed. This study investigated the effects of CaCl 2 and CaBr 2 on water flea Daphnia magna Straus in a 21-day reproduction test. The three tested concentrations of CaCl 2 (240, 481, and 1925 mg L -1 ) caused a significant dose-response decrease of reproduction (p<0.001). With CaBr 2 (533 and 1066 mg L -1 ), only aborted eggs were produced, demonstrating the embryotoxicity of the substance. The results suggest that high concentrations of the tested chemicals are harmful to Daphnia's reproduction and could reduce its abundance.

Background and purpose: Hyperosmotic solutions of calcium chloride and calcium bromide, extensively used in the oil industry, can be a source of aquatic pollution.Materials and methods: In the present study, we investigated whether the freshwater snail Planorbarius corneus L., previously chronically exposed to toxic concentrations of these chemicals, can recover fecundity and growth in clean water. We also examined if a higher tolerance could be induced in F1 offspring after parental and developmental chronic exposure to the chemicals.Results: The fitness-recovery study showed a high compensatory potential of the snails to recover fitness through increased reproduction and growth. In the tolerance study, we observed increased tolerance in F1 offspring in hyperosmotic solutions of calcium chloride. However, there was no significant improvement of reproduction performance in bromide-containing solutions.Conclusions: Increased tolerance was associated with a redirection of resources from growth to maintenance and survival.