Life-history consequences for Daphnia pulex exposed to pharmaceutical carbamazepine.

The effects of the antiepileptic, analgesic drug carbamazepine on the growth, morphology, and life-history characteristics of Daphnia pulex were examined at nominal concentrations of 0, 0.1, 1, 10, 100, and 200 microg L(-1). At 1 microg carbamazepine L(-1), Daphnia matured and reproduced slightly earlier than did controls, and at a given body length females produced more offspring than did controls or those receiving other treatments. In combination with a relatively high juvenile somatic growth rate and highest total number of progeny produced per female, carbamazepine at 1 microg L(-1) seemed to exert a stimulatory effect. The rates of population growth of the 100 and 200 microg L(-1) treatment groups was 9% and 32% lower, respectively, than the rates of growth of the controls and the Daphnia receiving treatments of up to 10 microg carbamazepine L(-1). At the highest dose, retardation of juvenile somatic growth resulted in delayed maturity and consequently in a lower rate of population growth. Adult somatic growth, spine length, reproductive output, and size of newborns were similar among treatments. Male offspring were only produced in the third broods, with broods that were 8% and 28% male at 1 and 10 microg L(-1), respectively. Neck teeth were never observed in Daphnia. Chronic adverse effects of carbamazepine on nontarget Daphnia were detected at 200 microg carbamazepine L(-1), but stimulatory effects might occur at environmentally realistic concentrations. However, additional studies of chronic toxicity investigating various combinations of pharmaceuticals and various environmental stresses, such as food condition, temperature, and kairomones, are needed to fully explore potential long-term adverse effects and to assess the environmental risk of common pharmaceuticals.