ABSTRACT: Ecotoxicogenomics in field experiments have yielded valuable mechanistic information for organisms present in polluted environments. The Queen conch (Strombus gigas) is a threatened species and populations are declining due to anthropogenic impact that includes pollution from boating activities. In the British Virgin Islands (BVI), local Queen conch populations have exhibited imposex, a condition in which both male and female gonadal characteristics are present and studies in the BVI suggest that tributyl tin (TBT), a chemical used in boat paint, is correlated to increased incidence imposex. This present study utilized a previously validated 8 x 15K Queen conch microarray to characterize the response of the ovarian transcriptome in conch found in polluted environments with high TBT in the BVIs. There polluted sites, Road Harbour (RH) and Trellis Bay (TB), are harbours with high boating activity while the reference sites, Guana Island (GI) and Anegada (AN), are areas with low boating activity. Microarray analysis revealed that there were 17 transcripts with high homology to known genes that were differentially expressed in the environments with high TBT and these included 6 induced and 11 down-regulated transcripts (p<0.01). These differentially expressed transcripts included phosphoenolpyruvate carboxylase, transposase, and high-affinity phosphate transporter PT1. When considering both RH and TB together in comparison to GI, functional enrichment showed that the biological processes and molecular functions of calcium ion binding, immune response, and negative regulation of cell proliferation were over represented in the polluted sites. Gene set enrichment analysis revealed that transcripts involved in the biological processes of general metabolism, immune, lipid metabolism, and stress were affected in polluted environments. Although difficult to directly link changes at the transcriptomics level to TBT in the harbour, this analysis provides novel insight into pathways impacted in regions that experience heavy boating activity in the BVIs. Adult female queen conchs were collected from field sites in the British Virgin Islands with varying levels of TBT contamination and imposex incidence. Contaminated sites included Rhode Harbour (RH, n=3) and Trellis Bay (TB, n=3), and the low-pollution site was Guana Island (GA, n=5). Ovaries were preserved in RNAlater, transported to the laboratory, and RNA was prepared using a phenol-chloroform extraction and a CsCl gradient. RNA was labeled with Cy3 for a single-dye design, per the Agilent protocol.
