Manmade chemicals affect fish spawning up to three generations later

By on April 6, 2015

Beyond direct impacts that endocrine-disrupting chemicals, like BPAs or hormones in birth control pills, have on fish, scientists at the U.S. Geological Survey have found that the chemicals can have adverse effects on fish offspring up to three generations later.

The finding helps illuminate effects the synthetic pollutants have on fish populations, and also reveals that adverse effects can be passed on through spawning.

“Our agency is focused on natural resource issues, including populations of fish, and as such we are concerned with fish exposure to these chemicals,” said Donald Tillitt, research toxicologist with the USGS. “There is so much we do not know, so studies like this one are intended to understand if adverse effects are even possible.”

Tillitt says that BPAs and EE2, the birth control hormone, were selected as target chemicals because they are easily modeled and can be measured in the environment.

He and others with the agency exposed Japanese medaka fish to the chemicals during their developmental stages to make the discovery, using concentrations that are higher than those found in nature. They then charted the effects to offspring, tracking things like gender reversals, fertilization rates and other reproductive abnormalities.

The medaka culture facility at the USGS’ Columbia Environmental Research Center. (Credit: Donald Tillitt)

The medaka culture facility at the USGS’ Columbia Environmental Research Center. (Credit: Donald Tillitt)

Initial exposure to the chemicals did not appear to impact embryonic development during the first week of observation, researchers write in the study published in Scientific Reports. But fertilization rates in the offspring of those embryos went down significantly two generations later. The generation after that saw a drop in embryo survival rates.

“This is the first study to show transgenerational effects of these two important model EDCs (endocrine-disrupting chemicals),” said Tillitt. “These are only the initial steps in understanding if this is a real phenomenon in wild populations of fish, or other wildlife for that matter.”

Since similar effects to offspring have been measured in mammals, the USGS researchers predicted that the same changes would be found with fish. Up next for the work is to look closer at interactions between endocrine disruptors in the natural world.

“Mixtures of EDCs can have joint action, that is work together,” said Tillitt. “Our next steps are to investigate lower concentrations to see if the same effects occur, and look into mixtures of EDCs.”

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