Abstract
The role of ecdysteroids in moulting and reproduction of Daphnia magna has been investigated. Further we examined whether previously observed moulting and reproduction disturbances in cadmium-exposed animals could be attributed to changes in ecdysteroid titres. Six concentrations of ecdysone and 20-hydroxyecdysone, ranging from 1 × 10 −8 M to 5 × 10 −6 M, were administered to daphnids exogenously. Treatment with high concentrations of both ecdysteroids resulted in unsuccessful exuviations and a decline in the number of progeny per female. The size of the neonates, however, appeared to be unaffected. 20-Hydroxyecdysone was demonstrated to be more effective than ecdysone. The presence of ecdysteroids in whole-body extracts of adult females was demonstrated using an enzyme-immunoassay. Additionally, ecdysteroid concentrations in daphnids were found to be affected by cadmium exposure at concentrations of 5.0, 10.0 and 20.0 μg/l. We concluded tentatively that changed ecdysteroid concentrations may have caused the moulting impairments in cadmium-exposed daphnids. On the other hand, there was no indication that the endocrine response of D. magna to cadmium exposure was also responsible for the cadmium-induced decline in neonate-size.
Published Version
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