Evaluation of environmental impact on natural populations of the Mediterranean killifish Aphanius fasciatus by quantitative RNA biomarkers.

The Mediterranean killifish, Aphanius fasciatus (Valenciennes, 1821) represents an excellent sentinel species for analysis of environmental impact in coastal areas. Quantitative changes on liver mRNA levels of five stress-related genes--metallothionein (metal exposure), vitellogenin, (estrogenic effects), cytochrome P4501A (CYP1A, dioxin-like compounds), superoxide dismutase (oxidative stress) and HSP70 (general stress)--were tested as markers of exposure to pollutants both in natural populations and in experimental treatments with model effectors. Analysis of fish from a metal-contaminated site in the Tunisian coast (Sfax) indicated that fish presenting spinal deformities (eight times more frequent at this site than in reference sites) showed increased levels of hepatic CYP1A mRNA levels compared to non-deformed fish from the same site or from the reference Louza site, suggesting a combined impact by metals and organic pollutants. Due to the strategy used in their design, these quantitative RNA markers will likely be useful to analyze environmental impacts on other related fish species.