Sperm and Salamanders
The low sperm count among rural Missouri males and the decline of the amphibious hellbender in the state's streams may be connected. But what is the cause?
St. Louis Post-Dispatch
By Jeffrey Bonner, President of Saint Louis Zoo
February 3, 2008
In the second of a monthly series this year, Saint Louis Zoo President Jeffrey Bonner explores a part of the globe where the Zoo is working to conserve threatened species, protect natural habitat and partner with other organizations to strengthen the web of life in which we all live.
If you're a young man - say a twentysomething - or you know a young man in that age range, it's a pretty safe bet that he's half the man his grandfather was. That's about how much sperm counts have fallen in industrialized nations over the last 50 years.
When the first definitive study of declining sperm counts was published in the British Medical Journal in 1992, it caused quite a furor. Studies since then have shown that sperm counts are continuing their steady decline, though not at the same rate everywhere. In Minneapolis, for example, the sperm counts are dropping fairly slowly.
But in rural Missouri, they're going down more rapidly.
I find this a little scary. I'm not just worried for my son, a twentysomething who lives in rural Missouri, but also for me. Sperm counts aren't falling because guys are wearing underwear that's too tight or spending too much time in the hot tub, although those two things certainly can cause sperm counts to drop. I'm worried because industrialized nations all over the world are experiencing something that is causing a clear deterioration in our overall health.
The declining sperm counts are just a symptom of a much bigger problem - a problem that affects us if we are male or female, young or old.
In 2003, the authors of a study of Missouri men found a strong link between trace amounts of herbicides in the men's urine and the quality of their semen. The authors concluded that men were exposed to the herbicides through public drinking water.
An Endangered Amphibian
Missouri's fast flowing streams are not just a ready source of drinking water in rural areas, but they're also home to both subspecies of a wonderfully ugly - and startlingly large - amphibious salamander called a hellbender. Hellbenders grow to about a foot long, hide under flat rocks while breathing through their skin and can live up to 50 years. They are especially fond of the rivers in which we like to canoe. In fact, Missouri canoeists have probably passed over dozens of hellbenders without knowing they were there.
About 12 years ago, scientists realized that our native hellbenders had virtually stopped reproducing. The mature ones were doing fine, but offspring were not being born in substantial numbers.
The Missouri Department of Conservation began to bring wild-caught hellbenders to the St. Louis Zoo for our reproductive scientists to examine. The females seemed to have plenty of eggs, but the males had poor sperm counts and high numbers of abnormal sperm. Because hellbenders spend virtually all their lives in the water, it could well be that whatever has made the male hellbender's sperm go bad is having much the same effect on us.
In laboratory tests, trace amounts of herbicides (which are present in the bodies of rural Missouri men) can cause male frogs to turn into hermaphrodites, creatures with male and female sex organs. Worse, the herbicides can cause those changes at concentrations of about one-tenth of a part per billion - 30 times lower than those deemed safe by the Environmental Protection Agency.
Of equal concern is many of the common drugs we consume. Their contents pass through our bodies, into sewage treatment plants and back into our rivers and streams. Estrogen, the active ingredient in many birth control pills, is one of these. In frogs, low levels of estrogen cause exposed tadpoles to become female; under normal conditions, half develop female and half develop male.
Tracking a Cause
So what is in the water that's harming our hellbenders? Could it be pesticides or herbicides? Growth hormones from cattle seeping into our watersheds? Estrogen?
Let's think about that last one a minute. It wouldn't take much estrogen, and there are a lot of canoeists. Most canoeists are young, that is to say of breeding age. Many of those breeding-age canoeists are females, and odds are many of those are on the pill. Canoeists can drink a lot on hot days on the river, and portable restrooms are few and far between. So, could estrogen present in female canoeists' urine be the culprit in the hellbenders' decline?
We don't know for certain. Estrogen is a possibility, but it is likely that multiple factors are at work altering the water quality. Because the bodies of hellbenders, like all amphibians, are like sponges, soaking up everything in their watery world, they are highly susceptible to changes in their environment.
At the Zoo, we're taking the first steps toward finding out exactly what's harming these incredible amphibians. In the basement of the herpetarium you'll find a replica of a Missouri stream. The temperature, oxygen levels, depth and current are timed to precisely mimic real conditions. Sprinklers come on to mimic rain and the light levels are adjusted to reflect the seasonal fluctuations in the length of daylight. Eight hellbenders live under large flat rocks, darting out to catch the crayfish that make up much of their diet in the Zoo and in the wild.
Last year, for the first time in history, females in our stream laid eggs and the males battled one another for the privilege of fertilizing them. One canny female stole some of the eggs, probably to cluster them around her own eggs so that a predator would eat her rival's first.
Unfortunately, none of the eggs hatched. We're hopeful that this year they will hatch, and we'll make history again. If we can get regular breeding and regular hatching, we can begin to subtly alter the water quality and measure the effects on the males' sperm, the females' eggs, and the number of offspring produced. Only then can we hope to unravel the mystery of why hellbenders have all but stopped reproducing in the wild.
At the same time, our nutrition scientists are intently studying and analyzing the diets of wild hellbenders. Perhaps the secret lies not in the water per se, but in what lives in the water that forms the hellbenders' diet. In St. Louis, our drinking water comes primarily from two rivers, the Missouri and the Mississippi. The headwater of the Mississippi is in Minnesota, which, as mentioned earlier, has more virile men than in much of Missouri.
We're proud of our water quality in St. Louis, but we're quite a ways downstream from the headwater. By the time you pour a glass of tap water from your kitchen faucet, you have no way of telling what elements that water has collected or how well it was treated on its way downstream.
We need to pay much more attention to what we're putting into our water, whether they be small streams or mighty rivers. We need to be careful of how we dispose of our waste oil, paint and solvents, careful of how much water we consume, careful to practice the best agricultural practices possible. We need to consider that a tiny bit of something that someone has poured (or excreted) into the water upstream can easily enter our bodies. And a tiny bit of something we put in our water can be ingested by someone in New Orleans.
Like Canaries in the Coal Mine
Why should anyone care about hellbenders? They are like the canaries in the coal mine. Our hellbenders and our frogs are giving us a warning: We can no longer treat our rivers and streams like giant natural sewers. Their power to self-cleanse is nearing - or has already passed - its limit. We can choose to swim in a stream; they can't. They live there.
If our Missouri streams are no longer safe for hellbenders to live in, how long will it be before it is unsafe for us to swim in them?
Republished with the permission of the St. Louis Post-Dispatch
Copyright 2008 St. Louis Post-Dispatch
Courtesy of STLtoday.com