Scientists conducted laboratory experiments on levonorgestrel (a synthetic progestin) and observed differential effects to males (reproductive behavior) and females (masculinization) of eastern mosquitofish (Gambusia holbrooki).
University of Maryland and U.S. Geological Survey (USGS) scientists examined the exposure effects of the synthetic progestin levonorgestrel (LNG) on the reproductive development and behavior of male and female eastern mosquitofish. Mosquitofish are viviparous (livebearing) fish that require internal fertilization and sex-specific behavioral displays to properly reproduce. Synthetic progestins, including LNG, are commonly used as components of human contraceptive and hormone replacement pharmaceuticals. Little is known, however, regarding the potential effects to aquatic organisms from exposure to such chemicals.
Scientists collaborated to conduct an 8-day laboratory aqueous exposure experiment. Eastern mosquitofish were exposed to LNG at three concentrations (0, 10, and 100 nanograms per liter, parts-per-trillion). The exposure concentrations were based on LNGconcentrations observed in wastewater effluent from the published literature. Although exposure levels based on effluent concentrations results are higher than likely expected in most streams, such levels are still environmentally relevant because it is not uncommon for some streams to be at, or approaching, 100 percent effluent under certain hydrologic conditions. Reproductive development was measured by determining anal fin (needed in males for internal fertilization of the females) length in female and male mosquitofish. The frequency of reproductive behavior was measured in paired exposure groups of males and females.
Scientists determined that LNG exposure affected female and male mosquitofish, but in substantially different ways. The females exposed to LNG exhibited physical changes (that is, masculinization evidenced by enhanced growth of the anal fin). Conversely, the males exposed to LNG exhibited behavioral changes (that is, spent less time performing courtship and reproductive behaviors). Males exposed to the highest LNG concentration developed elongated anal fins. This study documents that LNG exposures in a laboratory setting can affect the physical development and reproductive behavior of mosquitofish and indicates that these alterations could potentially affect wild fish in the environment.
This research is part of long-term investigations of the fate and effects of contaminants, including endocrine disrupting chemicals, by the USGS Toxic Substances Hydrology Program to provide water-resource managers with objective information that assists in the development of effective water management practices.
This research was funded by the USGS Ecosystems Mission Area’s Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology) and supported by grants from the Cosmos Club Foundation and Morris Animal Foundation.
Below are other science projects associated with this project.
Immunomodulation Science Team
Organic Geochemistry Research — Lawrence, Kansas
Fishing and Hunting Integrated Science Team
Gestodene Affects Fish Reproductive Behavior in Laboratory Exposure Study
Swine Manure Application as a Source of Hepatitis E Virus and other Livestock-Related Pathogens
Contaminants of Emerging Concern in the Environment
Complex Mixtures, Complex Responses—Using Comprehensive Approaches to Assess Pharmaceutical Effects on Fish
Long-Term Study Finds Endocrine Disrupting Chemicals in Urban Waterways
Endocrine Disrupting Chemicals Persist Downstream from the Source
Evidence of Endocrine Disruption Unexpectedly Found in Minnesota Lakes
- Overview
Scientists conducted laboratory experiments on levonorgestrel (a synthetic progestin) and observed differential effects to males (reproductive behavior) and females (masculinization) of eastern mosquitofish (Gambusia holbrooki).
Sources/Usage: Public Domain.On the left are photos of the anal fins of female (top left) and male (bottom left) mosquitofish that were not exposed to levonorgestrel (controls). On the right are photos of female (top right) and male (bottom right) mosquitofish that were exposed to 100 nanograms per liter (ng/L) levonorgestrel (LNG, nominal concentrations) for eight days. The exposure photos show that females exposed to LNG had masculinization as evidenced by enhanced growth of the anal fin, and the males exposed to the highest LNG concentration developed elongated anal fins. Modified from Frankel and others, 2016, figures 3 and 4. University of Maryland and U.S. Geological Survey (USGS) scientists examined the exposure effects of the synthetic progestin levonorgestrel (LNG) on the reproductive development and behavior of male and female eastern mosquitofish. Mosquitofish are viviparous (livebearing) fish that require internal fertilization and sex-specific behavioral displays to properly reproduce. Synthetic progestins, including LNG, are commonly used as components of human contraceptive and hormone replacement pharmaceuticals. Little is known, however, regarding the potential effects to aquatic organisms from exposure to such chemicals.
Scientists collaborated to conduct an 8-day laboratory aqueous exposure experiment. Eastern mosquitofish were exposed to LNG at three concentrations (0, 10, and 100 nanograms per liter, parts-per-trillion). The exposure concentrations were based on LNGconcentrations observed in wastewater effluent from the published literature. Although exposure levels based on effluent concentrations results are higher than likely expected in most streams, such levels are still environmentally relevant because it is not uncommon for some streams to be at, or approaching, 100 percent effluent under certain hydrologic conditions. Reproductive development was measured by determining anal fin (needed in males for internal fertilization of the females) length in female and male mosquitofish. The frequency of reproductive behavior was measured in paired exposure groups of males and females.
Scientists determined that LNG exposure affected female and male mosquitofish, but in substantially different ways. The females exposed to LNG exhibited physical changes (that is, masculinization evidenced by enhanced growth of the anal fin). Conversely, the males exposed to LNG exhibited behavioral changes (that is, spent less time performing courtship and reproductive behaviors). Males exposed to the highest LNG concentration developed elongated anal fins. This study documents that LNG exposures in a laboratory setting can affect the physical development and reproductive behavior of mosquitofish and indicates that these alterations could potentially affect wild fish in the environment.
This research is part of long-term investigations of the fate and effects of contaminants, including endocrine disrupting chemicals, by the USGS Toxic Substances Hydrology Program to provide water-resource managers with objective information that assists in the development of effective water management practices.
This research was funded by the USGS Ecosystems Mission Area’s Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology) and supported by grants from the Cosmos Club Foundation and Morris Animal Foundation.
- Science
Below are other science projects associated with this project.
Immunomodulation Science Team
The Immunomodulation Integrated Science Team focuses on contaminant and pathogen exposures in the environment that might influence the immune systems of wildlife and the connection to their shared environment with humans. In collaboration with public-health officials, the Team also addresses potential human-health risks stemming from similar exposures. If actual risks are identified, this Team...Organic Geochemistry Research — Lawrence, Kansas
About the ResearchThe Environmental Health Program collaborates with chemists and geologists at the Kansas Water Science Center's Organic Geochemistry Research Laboratory (OGRL) to develop targeted and non-targeted analytical methods for the identification and quantitation of chemicals that can impact the health of humans and other organisms and use bioassays to screen for receptor inhibition. The...Fishing and Hunting Integrated Science Team
The Fishing and Hunting integrated science team focuses on contaminant and pathogen exposures in the environment that could impact the presence and vitality of fish and wildlife populations that drive commercial, recreational and subsistence activities such as hunting and fishing. If actual risks are identified this project will inform how to economically and effectively minimize risk by providing...Gestodene Affects Fish Reproductive Behavior in Laboratory Exposure Study
Short-term laboratory exposure of adult fathead minnows to the human contraceptive progestin, gestodene (GES), at environmentally relevant concentrations induced rapid and negative effects on reproductive health and suggests that wild fish may be similarly affected.Swine Manure Application as a Source of Hepatitis E Virus and other Livestock-Related Pathogens
The presence of indicator bacteria, hepatitis E virus (HEV), and numerous bacterial pathogen genes increased following precipitation-induced runoff events in streams draining adjacent land surfaces in Iowa where swine manure was recently applied.Contaminants of Emerging Concern in the Environment
The USGS is conducting source-to-receptor research on a broad range of chemical and microbial contaminants including pharmaceuticals, personal care products, pathogens, antibiotic resistant genes, and natural toxins that are not commonly considered in environmental research but have the potential to impact environmental health.Complex Mixtures, Complex Responses—Using Comprehensive Approaches to Assess Pharmaceutical Effects on Fish
The occurrence of complex mixtures of prescription pharmaceuticals in streams and rivers around the globe has raised concerns about potential unintended adverse effects on aquatic organisms. The deleterious effects (for example, alteration of fish behavior) observed in this study confirm that effluents containing pharmaceuticals can adversely affect fish in ways that are central to sustaining...Long-Term Study Finds Endocrine Disrupting Chemicals in Urban Waterways
U.S. Geological Survey (USGS) scientists determined that endocrine disrupting chemicals (EDCs) were present in wastewater treatment plant (WWTP) effluent, water, and fish tissue in urban waterways in the Great Lakes and upper Mississippi River Regions (Indiana, Illinois, Michigan, Minnesota, and Ohio) during 1999 through 2009.Endocrine Disrupting Chemicals Persist Downstream from the Source
Endocrine disrupting chemicals (EDCs) were transported 2 kilometers downstream of a wastewater treatment plant (WWTP) outfall in a coastal plain stream. EDCs persisted downstream of the outfall with little change in the numbers of EDCs and limited decreases in EDC concentrations.Evidence of Endocrine Disruption Unexpectedly Found in Minnesota Lakes
Endocrine disrupting chemicals and indicators of endocrine disruption were found in several Minnesota lakes with surrounding urban, residential, agricultural, and forested land uses. The lakes do not directly receive discharges from industries or wastewater-treatment plants; however, they are used for recreation, and they receive water from widely scattered sources. The presence of both male and... - Publications