Indexed on: 01 Dec '91Published on: 01 Dec '91Published in: Water, air, and soil pollution
First and fourth instar C. riparius larvae hatched from the same egg mass were briefly exposed to equivalent assumed doses (mg hr) of Cd and adult emergence monitored for up to 50 days post hatch. Significantly more animals survived to emerge from control conditions than from any of the test solutions. For fourth instar larvae the presence or absence of artificial sediment during testing had no significant effect upon subsequent emergence. In terms of equivalent assumed doses, exposure to a high concentration for a short time resulted in a reduced emergence in comparison to exposure at a lower concentration for a longer time. There was a delay of several days between the time from hatch to first emergence and median emergence time for larvae exposed as fourth instars but not for those exposed at the first instar stage.