Environmental antiecdysteroids alter embryo development in the crustacean Daphnia magna

Abstract

The role of ecdysteroids in crustacean embryo development and the susceptibility of the developing embryo to the antiecdysteroidal properties of an environmental chemical were evaluated. The agricultural fungicide fenarimol was shown to exhibit antiecdysteroidal activity to the crustacean Daphnia magna by lowering endogenous ecdysone levels and delaying molting in a concentration-dependent fashion that was mitigated by co-exposure to exogenous 20-hydroxyecdysone. Exposure of either gravid maternal organisms or isolated embryos to fenarimol resulted in embryo abnormalities ranging from early partial developmental arrest to incomplete development of antennae and shell spines. Developmental abnormalities were associated with suppressed ecdysone levels in the embryos and the abnormalities could be prevented by co-exposure to 20-hydroxyecdysone. Developmental abnormalities caused by the antiecdysteroid were associated with reduced fecundity of the parental organisms. These results demonstrate that ecdysteroids are critical to normal crustacean embryo development and environmental antiecdysteroids can disrupt normal embryo development and compromise the production of viable offspring. Antiecdysteroidal activity may provide a means by which environmental chemicals impact crustacean species while not affecting vertebrates.

Inter-genotype variation in reproductive response to crowding among Daphnia pulex

“…These developmental abnormalities closely resemble those observed among neonates of D. magna individuals exposed to fenarimol (Mu & LeBlanc, 2002). Mu & LeBlanc (2002) further investigated the basis for the developmental abnormalities they observed, and found fenarimol exposure during embryo development to result in reduced ecdysone levels among neonates. We undertook no such biochemical tests of ecdysone levels among daphnids in our experiment.…”

Effects of chlordecone on 20-hydroxyecdysone concentration and chitobiase activity in a decapod crustacean, Macrobrachium rosenbergii

“…This hypothesis is supported by the studies of Hirano et al (2009) which have shown that low 20-HE concentration in the shrimp Americamysis bahia exposed to nonylphenol (also known to be an inhibitor of ecdysteroid activity) affected the growth of organisms. In similar way, a decrease of the 20-HE concentrations in juveniles of Daphnia magna exposed to the fungicide fenarimol was associated with abnormal development (LeBlanc, 2007;Mu and Leblanc, 2002). Snyder and Mulder (2001) have also suggested that the delay in the beginning of molting of larvae in the lobster H. americanus when exposed to heptachlor, probably correlated to a drop in the concentrations of circulating ecdysteroids.…”

Cloning and characterization of the ecdysone receptor and ultraspiracle protein from the water flea Daphnia magna

“…As in the case in other arthropods, Ec and JH play important roles in cladocerans (Baldwin et al 2001, Mu & LeBlanc 2002. The Ec affects male progeny production and chemicals related to JH increase male production in Daphnia magna and other daphnids (Peterson et al 2001, Tatarazako et al 2003.…”