Common weedkiller causes sex change in frogs

Written by: Captain Skellett // March 11th, 2010 // Uncategorized

That picture is two genetically male frogs doing the do. One of them has had a sex change, and is now a laydee frog with ovaries! Why has this happened? It’s been blamed on atrazine.

The paper
was published in the March early edition of PNAS. It adds further evidence against the weedkiller’s safety in an ongoing controversial debate.

Heading the team from California and Ohio was Dr. Tyrone Hayes of the University of California, Berkeley. Dr. Hayes has published several papers on the dangers of atrazine, a herbicide used extensively in Australia and the US. In the past he’s raised concerns that it can disrupt hormones even in small quantities, and this paper provides new evidence which is hard to ignore.

40 male frogs (Xenopus laevis) were raised from larva while exposed to 2.5 ppb atrazine. Their gender and testosterone levels were compared to male controls raised without the herbicide.

At sexual maturity 90% of the males exposed to atrazine had less testosterone than normal. In competition with control males, the atrazine treated frogs were less successful in mating. When they did mate, they were significantly less fertile.

The remaining four genetic males looked like females, and dissection of two revealed ovaries. The other two mated with control males and produced offspring which were all male.

Feminisation and decreased fertility spell disaster for frog populations. A drop in reproduction rate is bad enough, but it gets worse. With males masquerading as females they could breed themselves into extinction and we wouldn’t even know.

On the other hand, Dr. Hayes (pictured) has had a bit of a history with atrazine. I’d call it a crusade. He’s done a lot of research on it and some of it has been ripped to shreds by other researchers. In some cases his work has been deemed unreplicable, and that’s a big no-no in the science biz. Your results HAVE to be repeatable, otherwise it’s just not a good experiment.

On the other other hand, those people who’ve kicked the crap out of his work are largely people from EcoRisk, which are partially funded by the manufacturers of atrazine. It’s possible their designs were flawed so the amount of atrazine used wasn’t constant. Plus, well, it is a bit of a conflict of interest, right? But if that’s where the funding comes from…

So an activist on one side and a possibly bias company on the other. Hell, who’s right and who’s wrong? Do we want to take the risk? The Australian and US governments say that it’s a safe herbicide, but the European Union disagree.

While we wait for a decision, frogs may be the ones to suffer.

Or not.

Damn controversy.

Captain Skellett

I be Captain Skellett. Me blog started in April 2009 when I was working full time and didn’t get a chance to talk science. Now I have changed jobs and talk science all the time, but that doesn’t stop me blogging. More About Captain Skellett   Google


3 Responses to “Common weedkiller causes sex change in frogs”

  1. […] Continue reading here: Common weedkiller causes sex change in frogs | A Schooner of Science […]

  2. James says:

    I get why he is working with Xenopus but is there any indication this could happen to native frogs? Xenopus laevis are aka African Clawed Foot Frogs and are known to be a bit unusual developmentally.

    Yeah, I wondered the same thing. Plus it kinda seems that Xenopus (maybe frogs in general, not sure) change genders pretty happily. It would be really good to see if the results are the same using, say, the Green Tree Frog. I’d also like to get my hands on some research on how much atrazine can be found in rivers / groundwater in Australia from someone who’s not bias. Might try and track that down.

    He did mention some other studies using zebrafish and salmon that had similar effects from atrazine. Not to the sex changing extreme though.

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