Transcriptional effects in the estuarine guppy Poecilia vivipara exposed to sanitary sewage in laboratory and in situ

The urban growth has increased sanitary sewage discharges in coastal ecosystems, negatively affecting the aquatic biota. Mangroves, one of the most human-affected coastal biomes, are areas for reproduction and nursing of several species. In order to evaluate the effects of sanitary sewage effluents in mangrove species, this study assessed the hepatic transcriptional responses of guppy fish Poecilia vivipara exposed to sanitary sewage 33% (v:v), using suppressive subtraction hybridization (SSH), high throughput sequencing of RNA (Ion-proton) and quantification of transcript levels by qPCR of some identified genes in fish kept in a sewage-contaminated environment. Genes identified are related predominantly to xenobiotic biotransformation, immune system and sexual differentiation. The qPCR results confirmed the induction of cytochrome P450 1A (CYP1A), glutathione S transferase A-like (GST A-like) methyltransferase (MET) and UDP glycosyltransferase 1A (UDPGT1A), and repression of complement component C3 (C3), doublesex and mab-3 related transcription factor 1 (DMRT1), and transferrin (TF) in the laboratory experiment. In the field exposure, the transcript levels of CYP1A, DMRT1, MET, GST A-like and UDPGT1A were higher in fishes exposed at the contaminated sites compared to the reference site. Chemical analysis in fish from the laboratory and in situ experiments, and surface sediment from the sewage-contaminated sites revealed relevant levels of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyl (PCBs) and linear alkylbenzenes (LABs). These data reinforce the use of P. vivipara as a sentinel for monitoring environmental contamination in coastal regions.