Effects of animal starvation on the sensitivity of the freshwater amphipod Gammarus pulex to cadmium

Populations of amphipods experience different food availabilities during the year. This may alter their sensitivities to toxicants. However, there is scarce information about the effects of starvation on the tolerance to pollutants, and no data are available for the species Gammarus pulex. Our aim was to evaluate the effects of different levels of starvation on the short-term mortality of G. pulex on exposure to cadmium. Four levels of starvation (0, 3, 5 and 7days without food) were assessed using two exposure modes: semi-static (4days exposure to 0.10, 0.20 and 0.35mgCd center dot L-1) and two pulses (2 and 6h) of 2mgCd center dot L-1. LT50 and peLT50 values (post exposure) were calculated for each concentration and pulse, respectively. Our results show that starvation modifies the sensitivity of G. pulex. In general, at the lowest cadmium concentration (0.10mgCd center dot L-1) less-starved animals in semi-static exposure showed higher sensitivity to cadmium than more-starved animals. This trend was reversed for the highest cadmium exposure. Non-starved animals were more sensitive to cadmium applied in a short pulse than starved animals. Because natural populations are exposed to different food availability, starvation status has to be taken into account to assess the risk of toxicants.