Researcher Sara Hutton extracts RNA for qPCR to test gene expression of genes effected by pyrethroid exposure in the different generations of inland silverside fish. Credit: Sara Hutton
Key points:
- Researchers determined that fish exposed to pesticides at even low concentrations for a brief period of time can experience lasting behavior changes that impact their offspring.
- Fish exposed to pesticides demonstrated hypoactive behavior at the larval stage, while their offspring had hyperactive behavior.
- Fish use the same hormone receptors and steroids as humans, meaning that something that interferes with reproduction in fish could have the same effect on humans.
A new study, published in Environmental Science and Technology, reveals that fish exposed to pesticides at extremely low concentrations for a brief period of time can experience lasting behavior changes and impacts to their offspring.
Researchers used inland silversides as a model fish species along with three common pyrethroid pesticides—bifenthrin, cyfluthrin, and cyhalothrin. They exposed silverside embryos to pesticides for 96 hours at a concentration of 1 nanogram per liter of water. After the exposure, they placed larvae in clean water and reared them until five weeks post-hatch. They then moved the fish to larger tanks until reproductive maturity at which time they spawned the adult fish, collected their offspring, and measured behavior responses in parents and their offspring.
The researchers found that fish exposed to pesticides demonstrated hypoactive behavior at the larval stage. Conversely, their offspring, which had never been exposed to pesticides, demonstrated hyperactive behavior. Hyperactivity may be a compensatory adaptation to the hypoactive behavior of the previous generation, which comes at a cost to other biological processes such as growth and predation.
“This exposure is happening not just to these fish, but to all aquatic organisms in areas that are receiving runoff from areas populated by humans,” explained study author Susanne Brander, professor at Oregon State University. “It’s safe to say that we’re seeing influences at the population level if fish that were exposed for a few days as embryos and larvae are then producing offspring that are developmentally deformed.”
Additionally, the team determined that adult male fish exposed to bifenthrin and cyhalothrin pesticides as larvae had smaller gonads than the control group. The second generation of these fish had increased fecundity.
This study highlights the impact of early-life exposure to chemicals on fish. As fish use the same hormone receptors and steroids as humans, something that interferes with reproduction in fish could have the same effect on humans.
“In terms of environmental regulation, if we put stricter controls into effect because of studies like this, it’s going to take a few generations of fish—or whatever the organism is—for them to completely recover,” said Brander.