The trans-generation effect during pulsed cadmium exposure: tolerance and induction of hsp70.

Although the importance of pulse exposure has gained ground in recent years, it still needs to be better evaluated and understood. Two successive generations of Daphnia magna were exposed to four concentrations (40, 60, 80 and100µgCdl(-1)) of 6h cadmium (Cd) pulses. The increase of pulsed concentration of parent generation (F0) led to the decrease of EC50 and an increase of 21-day cumulative mortality of the first generation of offspring (F1). The mortality of F1 has a significantly higher level than F0 when they experienced the same pulse. Hsp70 can be induced by Cd pulse and gradually recover to the normal level after exposure. But the sensitivity of hsp70 of F1 was lower than F0 and the response seemingly was not under the control of heredity. Compared to growth, reproduction was more sensitive. The complete risk assessment of pulse exposure should take the response of offspring into account, especially in an ecological or field context.