REPRODUCTIVE STRATEGY OF DAPHNIA-MAGNA - IMPLICATIONS FOR CHRONIC TOXICITY TESTS

Food levels in Daphnia magna cultures did apparently not affect the sensitivity of the young in chronic toxicity tests. Variation in test results was mainly due to non-simultaneous replication of the tests. Reproduction of D. magna obviously is related to food rations. At low levels small broods of large neonates were produced, whereas at high food levels many tiny young were born. The ability to withstand starvation was shown to increase with the size of the neonate and with its lipid content. In chronic toxicity tests with cadmium and chromium, however, no unequivocal relationship was found between maternal food level and the sensitivity of the young. Differences in growth and reproduction between small and large neonates were not confirmed in a second experiment. Environmental circumstances during chronic tests were more important than maternal nutrition.