This Test Guideline is designed to assess effects of prolonged exposure to chemicals
on the reproduction and survival of the hermaphrodite freshwater snail Lymnaea stagnalis
(the Great Pond Snail). Reproducing adults of L. stagnalis are exposed to a concentration
range of the test chemical and monitored for 28 days for their survival and reproduction
(number of egg clutches). As additional information, the number of eggs per clutch
may also be determined. Adult shell length increase may also be measured. The toxic
effect of the test chemical on the cumulated number of clutches produced per individual-day
is expressed as ECx by fitting an appropriate regression model to the data in order
to estimate the concentration that would cause x% reduction in the reproductive output.
Alternatively, the toxic effect of the test chemical can be expressed as the No Observed
Effect Concentration and Lowest Observed Effect Concentration (NOEC/LOEC) values.
Both ECx and NOEC/LOEC can be determined from a single study.