New chemicals which have not yet been approved and harm the mudsnail in Organisation for Economic Co-operation and Development (OECD) Test No. 242 in the laboratory would have the same effect on it and related species in the wild. Since molluscs, after insects and crustaceans, are the second most species-rich group in the animal kingdom, the loss of these organisms would be fatal for biodiversity and thus also for the correct functioning of the ecosystems. The development of the “snail test” therefore constitutes an important contribution to keeping our watercourses clean and healthy, since substances which show a toxic effect in this test for the snail can in future be identified and controlled prior to market introduction.
In their home country of New Zealand, both male and female mudsnails are found. In Europe, however, populations are composed solely of females which reproduce parthenogenetically. This makes using the test and analyzing the results easier, all the more so since the tiny snail makes only modest demands on the laboratory.
In addition, the new snail test closes an existing gap in the environmental risk assessment of chemicals, since standardized tests with invertebrates to date focused mainly on arthropods (insects and crustaceans). Snails had, however, in the past proven to be extraordinarily sensitive to a large number of substances, including tributyltin compounds and other environmental chemicals which are claimed tp influence the hormone system.
Test conditions for the snails with regard to water and feedstuff quality, temperature, concentration and numerous other parameters were optimized in the framework of an extensive research program. In the last six years, four final validation studies with six test substances were carried out in 16 laboratories in Europe and the USA which showed that the test protocol developed is robust and the test generates reproducible results, independent of in which laboratory it is implemented.
For the test, female mudsnails are exposed to a concentration range of chemicals in ambient water. The organisms remain with the test substance in their test beakers for 28 days, after which the number of embryo amongst all surviving females is counted.
Reference: OECD (2016), Test No. 242: Potamopyrgus antipodarum Reproduction Test, OECD Publishing, Paris. DOI: http://dx.doi.org/10.1787/9789264264311-en