Clonal variation in general responses of Daphnia magna Straus to toxic stress. I. Chronic life-history effects

Compares responses of different genotypes of D. magna to cadmium and 3.4-dichloroaniline, under acute and chronic exposure. Large differences in interclonal responses were observed in acute tolerance to Cd (range of LC₅₀: 0.06 - >100 ppb). Interclonal variation in chronic stress tolerance was also observed, although in this case differences (though significant) were relatively small (effect concentrations 25-50 ppb for DCA and 0.6-6.0 ppb for Cd). Deleterious effects on life-history variables and energy allocation followed the same pattern for all clones exposed to both toxicants. Specific mechanisms dominate differences in acute responses, whereas general mechanisms dominate in chronic responses. -from Authors