PAH effects on grass shrimp, Palaeomonetes pugio: interactions with the ecdysteroid system

The steroid hormone ecdysone controls molting and differentiation in Arthropods. We used a multi-tiered approach to investigate whether polycyclic aromatic hydrocarbons (PAHs) interact with the functional Ecdysone Receptor (EcR) in vitro, and whether PAHs have molting or reproductive effects in vivo. We focused on four PAHs: pyrene, benzo[a]pyrene, benzo[b]fluoranthene, and chrysene. A reporter gene assay using a Chinese hamster ovary cell line which stably expresses the EcR/RXR complex, showed that the four PAHs had no agonistic activity, but were able to enhance reporter gene expression when given in conjuction with an ecdysteroid agonist, muristerone A. An ecdysone-responsive Drosophila cell line (Cl 8+) showed that PAHs alone had no effect, but were able to enhance the differentiation response in the presence of muristerone A. Finally, ablated grass shrimp (Palaeomonetes spp.) were exposed to 100 nM chrysene, and molted approximately 12 h earlier than the vehicle controls. Since chrysene was able to enhance reporter gene activation and the Cl 8+ cellular response in the presence of an ecdysteroid, the accelerated molting correlates well with the in vitro assays. A chronic 8 week exposure study on intact shrimp is currently underway to determine molting and reproductive endpoints, as well as P450 and lipovitellin levels.