Effects of Small Concentrations of Endocrine Disrupting Chemicals Impact Three Generations of Fish

Fish exposed to endocrine-disrupting chemicals can pass the impacts on future generations of fish even only the parent fish is directly exposed to the particular chemicals.

This was the finding of a study of researchers from Oregon State University lead by Kaley Major. The study, which was published in the journal Frontiers in Marine Science, focused on the impact of endocrine disruptors to inland silversides, Menidia beryllina, a fish that inhabits estuaries in eastern North America and the Gulf of Mexico. It has also been introduced in California.

Inland silversides feed on zooplanktons and are eaten by birds and commercially valuable fish.

Endocrine disruptors, the harmful chemicals focused on this study, imitate the hormones of the body.

Endocrine disruptors are commonly found in chemicals at home or for industrial uses: it is present in flame retardants, pesticides, cosmetics to toys, and even food. Previous studies have reported that such chemicals caused altered sex ratios, lower fertility rates, and deformities in fish.

Even animals, including humans, were documented to be affected with endocrine disruptors as well: it alters the body's natural hormones that are responsible for development, behavior, and fertility. Research has also shown that its adverse effects on humans are passed on to generations.

In the study, inland silversides were placed in an Olympic-sized pool and were exposed to a few drops of each endocrine disruptors. The researchers studied three generations of the fish for 21 months to see if the exposure to endocrine disruptors to parents can be passed on from generation to generation.

Previous researches had reported the negative impacts on fish exposed to high levels of endocrine disruptors. Only a minimal number of studies, however, report the effect of the said chemical to fish at low levels of exposure. This particular study focused on the impacts of a small level of exposure from the endocrine disruptors.

According to Susanne Brander, an assistant professor and aquatic toxicologist of Oregon State University, they understand how animals deal with stress in the environment, especially when new stressors are introduced every day important.

"Our research helps show what animals do to respond to these changes and how quickly they can respond to them," Brander said. These responses will provide them an understanding of the impact in the environment, in the long run, she added.

To track the development of the fish, methylation, a process by which carbon and hydrogen known as a methyl group, is added to a DNA molecule. Methylation helps track the DNA molecule and indicates how an organism develops.

More importantly, previous studies indicate that endocrine disruptors have sometimes caused changes in gene expression and DNA methylation. But since previous studies have used high concentrations of endocrine disruptors, the study team wondered whether the low concentration of endocrine disruptors could impact methylation in fish that live in estuaries.

To the study team's surprise, patterns of methylation were consistent across the three generations of fish that they studied, even though only the first generation was exposed to endocrine disruptors for a few weeks in its early life.

Further research to help experts understand more about methylation markers and how pollutants may affect the evolution of inland silversides is necessary.