Shrnutí

Popis

The eggs, larvae, and juveniles of horseshoe crabs L. polyphemus contribute significantly to the forage base of many species in Delaware Bay. The eggs also provide a crucial forage base for at least 11 species of shorebird. Birds foraging on L. polyphemus eggs significantly contribute to the wildlifewatching industry in Delaware and New Jersey. L. polyphemus also has significant economic importance to the bait fishery and the pharmaceutical industry. Estimates suggest the population of L. polyphemus in Delaware Bay have declined. Disease, harvest for bait, and habitat loss may contribute to the apparent population decline. However, environmental contamination also may play a role. This investigation looked at potential adverse effects to L. polyphemus by the endocrine disrupting pesticide methoprene. Methoprene is an insect growth regulator that acts as a juvenile hormone mimic. Land managers apply methoprene aerially to marshes of Delaware Bay to control mosquitoes. This investigation hypothesized that mosquitoes and L. polyphemus will experience similar adverse effects from a compound like methoprene. Two procedures were used to assess these effects. First, any macroscopic developmental abnormalities were recorded by observing egg and larval development in vitro. Second, a proteomics approach was used to address the multitude of potential pathways that may become altered as a result of methoprene exposure. The proteomics approach involved three phases: 1 separation and visualization of unknown proteins that are expressed differently in controls as compared to treated eggs, embryos, and potentially larvae; 2 visualization of those proteins that are consistently over or underexpressed in treated individuals compared to controls; and 3 identification of these proteins by de novo amino acid sequencing. A total of 55 female and 22 male adult crabs were collected from Kimbles Beach at Cape May National Wildlife Refuge for two separate spawns. Phase I of the investigation examined embryo, larval, and juvenile response to a series of exposures to methoprene solutions at 0 gl, 1 g, 10 gl, and 100 gl using pore water from Kimbles Beach and artificial sea water. Eggs, embryos, larvae, and juveniles were monitored for fertilization, hatching, and survival and for any macroscopic abnormities. Eggs and larvae all treatments were periodically removed and archived in liquid nitrogen for later proteomic analysis. Phase II of the investigation involved a proteomics approach to observing whether the methoprene may have caused more subtle effects to the embryos, larvae, and juveniles. The results provided no evidence that a treatment effect occurred. We observed no obvious acute effects of environmentally relevant concentrations of the mosquito larvicide methoprene on developing L. polyphemus embryos, larvae, or first molt post hatch juveniles. Through this investigation we found evidence for a No Observed Adverse Effects Level of 100 gl for methoprene exposure. Our findings provide evidence that chemical exposure to methoprene may not be a limiting factor to the population of L. polyphemus. This information will be useful to land managers, agencies involved in mosquito control, and the numerous groups interested in finding and examining the limiting factors on the L. polyphemus population.