ZOU, E.; Nicholls State University: Impact of Xenobiotics on Crustacean Molting

Endocrine disruption by anthropogenic chemicals has been well documented for vertebrates, but has not been extensively studied for invertebrates except the imposex phenomenon in gastropods. Crustaceans are one of the larger animal groups. Concern has been expressed over the possibility that the same environmental agents that interfere with endocrine functions of vertebrates may also perturb hormonally regulated processes of crustaceans. My studies with Daphnia magna have shown that the estrogenic xenobiotics diethylstilbestrol (DES), endosulfan, Aroclor 1242, and diethyl phthalate, and the putative estrogenic agent 2,4,5-trichlorobiphenyl (PCB29) inhibit molting of daphnids. To gain insight into the mechanisms for the inhibition of molting by these estrogenic agents, a larger crustacean model, the fiddler crab, Uca pugilator, was used. It was found that the delay of molting in the presence of these estrogenic xenobiotics can at least be partly accounted for by the inhibition of activity of chitobiase (also known as N-acetyl-β-glucosaminidase) in the epidermis of Uca pugilator since this enzyme is essential for degradation of the old chitinous exoskeleton. Because activity of chitobiase is regulated by the molting hormone 20-hydroxyecdysone and none of the above chemicals are capable of inhibiting chitobiase activity in vitro, the inhibition of chitobiase activity in the presence of these xenobiotics strongly suggests that exposure to these compounds disturbs the Y-organ-ecdysteroid receptor axis in Uca pugilator.