Linking feeding activity and maturation of Daphnia magna following short-term exposure to fenvalerate.

Feeding activity and maturation were investigated in Daphnia magna exposed to fenvalerate for 24 h. The feeding activity was monitored by measuring filtration rates and 15N-traced food assimilation. Exposure resulted in individuals with reduced feeding activity and smaller body size at concentrations of 0.3 microg/L or greater as well as delayed maturation at concentrations of 0.61microg/L or greater. Filtration rates recovered within 2 d of the exposure, but long-term effects of reduced feeding activity, such as growth retardation, occurred. Because D. magna needs to reach a minimum size to mature, growth retardation may explain the observed delay in maturity. The proposed causal relationships suggest that exposure to fenvalerate reduces feeding activity, resulting in growth retardation, which leads to delayed maturity. In cases of exposure to such toxicants, the monitoring of feeding activity may predict long-term effects on population parameters.