Columbia researchers study intersex sturgeon in Missouri River

Monday, December 6, 2010 | 10:38 p.m. CST; updated 11:54 a.m. CST, Tuesday, December 7, 2010
Ecologist Aaron DeLonay, with the U.S. Geological Survey, holds a shovelnose sturgeon netted just east of Jefferson City on the Missouri River that he estimates to be 3 or 4 years old Oct. 29. DeLonay and a small team of scientists go out on the river frequently to check on the reproductive condition of a more rare fish, the pallid sturgeon, to see, and in some cases ensure, successful reproduction. Whenever DeLonay and his team catch a pallid sturgeon that they have not caught before, they implant a tracking device that, other than tracking water depth and temperature, can be used to determine if the fish mated.

COLUMBIA — Donald Tillitt was in his office at the Columbia Environmental Research Center when he received a call.

“You need to come back here and look at these,” Tillitt recalls biologist and colleague Diana Papoulias saying.

Intersex studies and medication disposal methods

Breakdown of Missouri River sturgeon studies


  • Intersex sturgeon from a Missouri River site south of Columbia were discovered by the Columbia Environmental Research Center.
  • The center expanded its ongoing research to focus on the presence of intersex shovelnose sturgeon, their reproductive behavior and a possible connection to contaminants.
  • Every month for the next year the center took 30 shovelnose sturgeon, 15 male and 15 female, from a Missouri River site near Boonville.
  • Of the groups of 30 fish repeatedly taken from the site, about 7 percent, or 25 total fish, had male and female characteristics. Normal males and normal females were observed in addition to a high percentage of males with both eggs and sperm.


  • The effects of common contaminants of the Missouri River, such as PCBs, DDT and organochlorine pesticides on intersex fish rates were studied, but no correlation was found.
  • The center continued to observe intersex characteristics in shovelnose and the endangered pallid sturgeon. Researchers noticed other sexual anomalies including malformed testes and teratomas.


  • The center teams up with the Missouri Department of Conservation to expand its research to other Missouri and Mississippi river sites, including locations near: St. Joseph, St. Louis, Kansas City, Crystal City and Columbia.
  • For this study, scientists repeatedly caught 15 to 20 male fish per site. Outside of the urban areas, intersex rates sometimes shot up to 23 percent.


  • The center developed proposals with the U.S. Fish and Wildlife Service to start studying the effect of ethinyl estradiol and other hormonal compounds on shovelnose sturgeon.

Intersex around the world

  1. One of the many facets of a U.S. Geological Survey study involved research of 16 different fish species in nine river basins, but largemouth and smallmouth black bass showed most signs of being intersexual. Three percent or 97 of 3,110 fish had intersex traits. Though hormone compounds were not linked to these traits in this study, scientists suspect these compounds, as well as other factors including age, collection season and environment play a role in causing intersex. These river basins had intersex fish in varying amounts:
    • Mississippi River Basin
    • Columbia River Basin
    • Rio Grande River Basin
    • Colorado River Basin
    • Apalachicola River Basin
    • Mobile River Basin
    • Pee Dee River Basin
    • Savannah River Basin
    Intersex fish were not found in the Yukon River Basin.
  2. According to a report by Chemicals, Health and Environment Monitoring Trust, a British organization that aims to raise awareness about the effects of chemicals on humans and wildlife, intersex fish have been found in the UK. Fish have been found with vitellogenin, a female egg yolk, in freshwater estuaries, particularly in water downstream from sewage treatment plants. Oestrone, ethinyl estradiol and industrial contaminants such as nonylphenol have been found in the waters.
  3. According to an Environmental Health Perspectives research article, intersex fish have been found in:
    • Italy
    • The United Kingdom
    • Canada
  4. A study published in Toxicological Sciences in 2001 outlined the results of subjecting the Japanese medaka fish to ethinyl estradiol. The results were complicated. Adult fish were found to be affected by ethinyl estradiol, while medaka in the developmental stages were unaffected. The adult female fish experienced decreased egg production and changes in egg size, depending on how long they were exposed. Researchers said timing and frequency of exposure were key factors to understanding the effects of ethinyl estradiol.

How to dispose of unwanted medications:

Drug compounds get into surface water when people improperly dispose of medications, not just through human waste. The city of Columbia’s website recommends unwanted medications be taken to the Household Hazardous Waste Facility at 1313 Lakeview Drive (near the power plant, off Business Loop). It's open the first and third Saturdays of April through November from 9 a.m. to 1 p.m.

You can also dispose of medications in the household trash if you follow these precautions:

  • Keep products in their original container. Remove label or conceal personal information with a permanent marker.
  • To make the drug unusable, add a small amount of water to a solid drug and recap the container. For liquids, add some absorbent material such as kitty litter, sawdust or flour.
  • Place the container in another container or a heavy bag.
  • Place item in the trash.

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The year was 2000 and the U.S. Geological Survey research center on New Haven Road was dissecting shovelnose sturgeon from a site south of Columbia in the Missouri River. By studying the reproduction of the species, scientists hoped they could shed light on decreasing populations of a similar but endangered species — the pallid sturgeon.

When Tillitt looked inside the fish before him he saw ovarian tissue — black eggs — growing around white testicular tissue. It had the fully developed sex organs of both a male and a female sturgeon.

Though fish with both male and female sexual characteristics have been observed throughout the world in the past decade, the Missouri River intersex sturgeon are unusual. Usually scientists observe this condition with microscopes, Tillitt said. But intersex characteristics in the Missouri River sturgeon are so highly developed they are visible to the naked eye.

“It was very evident and very clear that we were seeing something abnormal,” Tillitt said.

The dramatic nature of the intersex condition in shovelnose sturgeon has sparked research into the cause of the condition, as well as other unknown consequences for fish.

Though the center does not yet know how intersex affects the reproduction of shovelnose sturgeon, a recent study in England showed that intersex reduced reproduction in male fish by up to 76 percent.

For humans, the research raises questions about the role of hormonal compounds from birth control pills and other drugs that make their way from toilets into rivers and streams.

Calls made by Papoulias to national and international labs confirmed that intersex in shovelnose sturgeon is one of the most dramatically developed cases in the world. Fully developed intersexual sturgeon are rarely reported in the United States and are seen only in a few places around the world such as highly contaminated rivers in Russia.

Many scientists, including Papoulia and Tillitt, believe the majority of the intersex sturgeon found are feminized males because they contain more testicular tissue than ovarian tissue.

Intersex fish may be linked to hormonal compounds in pharmaceuticals

Intersex in some fish species has been linked to the presence of hormonal compounds in surface water, such as those found in birth control pills and hormone replacement drugs.

Ethinyl estradiol, a major component of birth control pills, as well as other similar drugs, can enter rivers and other surface waters through human waste. These compounds are flushed down the toilet and travel to wastewater treatment plants. These compounds also enter wastewater when people flush unwanted medications down the toilet.

The systems that most treatment plants use today, including the Columbia Regional Wastewater Treatment Plant, do not effectively remove chemical compounds from water, said Craig Cuvellier, a laboratory supervisor who works at the plant.

Filtration technology that removes chemical compounds is extremely expensive and not viable for most wastewater treatment plants, Cuvellier said. He said other methods to remove pharmaceuticals from water are under study.

The Columbia Environmental Research Center has not done enough studies to link the sturgeon intersex to these specific contaminants. But scientists at the center believe hormonal contaminants are a likely factor; other studies have implicated a link between these compounds and intersex characteristics in different species of fish, Tillitt said.

Until 2008, the center studied normal reproductive patterns for sturgeon, as well as the effects of common contaminants in the Missouri River such as pesticides and polychlorinated biphenyl, or PCBs, on intersex rates.

No correlation was found between the feminization of fish and these common contaminants, Papoulias said. The center said the next step is studying long-term exposures of shovelnose sturgeon to hormonal compounds, including ethinyl estradiol.

Previous studies might not have studied the right compounds

It will take more years of studies for the center to discover the cause of intersex sturgeon, though the center has engaged in similar research before. One facet of a series of U.S. Geological Survey studies of fish in nine river basins across the country from 1995-2004 was the examination of reproductive organs in an attempt to understand the geographic spread of intersex fish across the nation.

Intersex fish were found in 97 of the 3,110 samples, or 3 percent, of those collected and in four of 16 species studied. Largemouth and smallmouth bass were affected the most. Female characteristics were found in 18 percent of largemouth bass males and 33 percent of smallmouth bass males.

Scientists noticed the presence of chemicals known to disrupt hormones and cell behavior, such as pesticides, in the tissue of fish from various rivers, but they could not correlate them with sexual characteristics because the condition sometimes appeared in fish in areas with low concentrations of these chemicals.

Chemical contaminants may not have been the only cause of this condition in the bass studied or the current sturgeon study, Tillitt and Papoulias said. Temperature, dissolved oxygen and other environmental factors can influence sexual development.

Papoulias also said that the species of the fish is key in determining how or why such a condition develops. Scientists still do not understand why or how this condition is seen in some species but not others; it is very possible sturgeon and bass are more susceptible or sensitive to certain hormonal compounds or other chemicals. 

After the national survey, scientists concluded that they needed to study other factors that could be responsible. They also acknowledged another aspect of trying to understand the cause — they may have studied the wrong compounds, Papoulias said.

The future is unclear as scientists continue to look for answers

The search for the cause of intersex phenomenon in shovelnose sturgeon continues along with efforts to understand why the pallid sturgeon is endangered.

Aaron DeLonay, an ecologist for the river studies branch of the research center in Columbia, works primarily on the Missouri River monitoring the reproductive behavior of pallid sturgeon.

The two branches collaborate by equipping fish with transmitters for monitoring purposes, capturing them to take blood samples, looking at sex organs to detect anomalies and using ultrasound to see where fish are in the reproduction process. Researchers study how changes in environment and habitat affect sturgeon behavior, including reproductive organs.

Scientists continue to study why the pallid sturgeon population is not improving, DeLonay said. Intersex has been observed in a few pallid sturgeon, but the condition is harder to study because there are fewer fish. He said shovelnose populations have also decreased since 2000, though not to the extent of pallid sturgeon.

Contaminants, as well as habitat changes and river projects such as dams that disrupt water flow, are thought to be potential causes for the pallid sturgeon decreases, DeLonay said.

As the center prepares for more contaminant tests on the shovelnose sturgeon, Papoulias is in the process of preparing a research paper outlining the sturgeon studies in the past decade.

Scientists hope to learn more about hormonal compounds as they prepare to subject sturgeon to the ethinyl estradiol for more studies. The primary compound in birth control pills is an important contaminant to study for many reasons, Tillitt said.

The compound is a good model for the various kinds of estrogen; scientists hope that information obtained about ethinyl estradiol can apply to many other types of hormonal compounds consistently observed in water.

“We are trying to understand the mechanisms of how this occurs,” Tillitt said. “We know that estrogen can interact with an estrogen receptor and they turn certain genes on and certain genes off.”

Although the process could take a long time, Tillitt said, the center hopes for breakthroughs because fish health reflects the health of the environment.

“It’s important to understand so we can understand more about the health of our fish and wildlife and really the health of our environment — because we live in this environment as well,” Tillitt said.

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Michael Williams December 7, 2010 | 10:23 a.m.

Finally....a popular press article on ethinyl estradiol, estrone, and other hormonal replacements. I was beginning to feel like a lone voice in the wilderness for the last 12 years, poor me.

Folks think that ingested hormones just do their job and disappear. Not so. Some of the hormones may be metabolized to more or less biologically-active agents, some remain as parent compounds, but all get excreted into sewers and, eventually, waters of this state. In many places throughout the world, concentrations of these chemicals in waters meet-or-exceed those levels KNOWN to cause adverse effects on laboratory organisms. We are talking about concentrations in the parts per trillion and low parts per billion. These are quite potent chemicals!

What a huge political problem this is, and it's not being talked about! Ethinyl estradiol is THE primary method for family planning in the world. Are you willing to tell a woman she must not use these chemicals because of concerns about feminized fish, lesbian birds, and smaller alligator penises?

Thanks, Missourian, for writing about this. Perhaps we can start doing more exhaustive research into these problems instead of picking/choosing our chemical criminals based upon politics and agendas.

(Report Comment)
Steve Schnarr December 9, 2010 | 10:22 a.m.

Thanks for a really well researched and even-handed article. It's important to realize that, although Columbia gets its drinking water from wells located in the Missouri River floodplain, over 40% of the state's population gets treated drinking water directly from the Missouri River. "Emerging" contaminants such as pharmaceuticals and hormone treatments are not removed in the treatment process.

(Report Comment)
Mark Foecking December 9, 2010 | 11:01 a.m.

Michael, here's a new article that you might be interested in. They're saying that feedlots and natural estrogens are a far greater source of estrogenic activity than contraceptives.


(Report Comment)

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