Mervyn and I went to visit what was last year a great pond for Common Toads in Essex, sadly it now has 9/10ths cover of what I believe to be Floating Pennywort Hydrocotyle ranunculoides. The tadpoles were restricted to a small area kept clear by the local dogs taking a paddle. There were a good number of toadlets and froglets about in the margins, I just hope those who manage the site act to eradicate the pennywort before next season.

Floating Pennywort

Emerging Common Toad

"Shoal" of Common Toad Tadpoles

Thanks for the pics Gemma.

Shame about that weed taking over though. I read a short while ago that there is a chemical in garden pond weedkillers (Supposedly Harmless to fish and other pond life), that causes frogs to develop both male and female genetalia.

Alan

Hi Alan,

I don't think it's very clear in the picture, but the shoal extends to the left towards the top of the image. The whole thing seems to move in a coordinated fashion, the tadpoles move both up and down using the depth of the water and those at the back seem to follow those at the front as it moves around - I guess it has to be seen really!

Bit unfortunate for the frogs about the herbicide! I can't see anyway of eradicating the stuff though other than using chemicals, it grows at 15-30cm a day (yes a day!) and will soon block all light from the pond. It's also a danger to the public as it forms a dense mat of it's own roots, giving the appearance of a solid surface even over deep water. Hopefully EN will be successful  at banning it's import.

http://www.english-nature.org.uk/news/story.asp?ID=75

Hi Gemma,

I bet that is really cool, I'll have to keep my eye open for toad tads in the future.

The herbicide/ Frog genatalia thing isn't proven as far as I know. A guy I knew posted an article from some science magazine about it on another board about a year ago. I've not heard anything about it since.

Cheers,

Alan

Seems to be quite a bit on american sites about this, but many doubts about the study too.

Herbicide Blamed for Frog Mutation

Reprinted from the newsletter of the St. Louis Herpetological Society, Vol.29, No.5, May 2002.

April 15, 2002, WASHINGTON (AP) -- Male frogs exposed to even very low doses of a common weed killer can develop multiple sex organs - sometimes both male and female - researchers in California have discovered. "I was very much surprised," at the impact of atrazine on developing frogs, said Tyrone B. Hayes of the University of California at Berkeley.

Atrazine is the most commonly used weed killer in North America, he said, and can be found in rainwater, snow runoff and ground water. "There is virtually no atrazine-free environment," Hayes said.

The Environmental Protection Agency permits up to 3 parts per billion of atrazine in drinking water. But Hayes' team found it affected frogs at doses as small as O.1 parts per billion. As the amount of atrazine increased, as many as 20 percent of frogs exposed during their early development produced multiple sex organs or had both male and female organs. Many had small, feminized larynxes.

Hayes' research team concluded that the effect on the frogs results from atrazine causing cells to produce the enzyme aromatase, which is present in vertebrates and converts the male hormone testosterone to the female hormone estrogen.

The effects on frogs in Hayes' study occurred at exposure levels more than 600 times lower than the dose that has been seen to induce aromatase production in human cells.

Their research is reported in Tuesday's issue of Proceedings of the National Academy of Science.

Asked if atrazine might also be a threat to people at low levels, Hayes said he did not know, adding that, unlike frogs, "we're not in the water all the time."

Copyright ® 2002, Colorado Herpetological Society. All rights reserved.

There is a way of controlling pennywort, that I've found in my pond. I wouldn't recommend it in the wild though. My red eared terrapins love the stuff and munch it faster than it grows, to the point of local extinction here!!

Martin.