Poison Frogs

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Sometimes nature stuff can be fairly interesting reads.

http://www.livescience.com/animalworld/ ... frogs.html

Convergent Evolution in Poison Frogs
By Bjorn Carey
LiveScience Staff Writer
posted: 08 August 2005
05:22 pm ET

Scientists have discovered one of the most intricate examples of convergent evolution with the help of South American "poison" frogs and ants and their cousins in Madagascar. (And here’s an odd fact for smokers: one Madagascan frog studied was found to have nicotine in its system!)

Poison frogs can’t make their own poison—they steal it from ants. Poison frogs secrete a variety of chemicals called alkaloids to create a poisonous defense against predators. Since they can’t produce alkaloids on their own, these frogs maintain a steady diet of specific alkaloid-rich ants to keep up their defense.

Now, Valerie Clark of Cornell University and her colleagues have detailed two instances of convergent evolution—the process in which organisms not closely related independently acquire similar characteristics while evolving in separate ecosystems—between frogs and ants on two continents.

First, species of ants high in alkaloids had to evolve on two separate continents.

"The ants had to be there with alkaloids for the frogs to evolve to get alkaloids in their skin," Clark told LiveScience.

Then the frogs had to develop a resistance to the alkaloids—instead of spitting out the ants or passing the alkaloids through their systems, the frogs became able to keep their ant dinners down. Then they evolved to make use of the alkaloids themselves.

Also, both the frogs in South America and Madagascar evolved to have "don’t-eat-me" skin colorings, the final step in a remarkable tale of multi-step convergent evolution.

Up until now, scientists have mainly studied frogs from South America and Australia. But Clark and her colleagues showed that the Madagascan frogs needed the same types of food to be poisonous.

They examined the stomach contents of 21 frogs from the genus Mantella and found that alkaloid rich ants made up 67 percent of their food intake.

Not only that, but they found nicotine—the same chemical found in cigarettes—in one Mantella baroni frog out of 22 examined. Nicotine is produced by plants and can sometimes be found in animals that eat these plants. But so far no nicotine-producing plants have been found growing in the area where this frog was found. This was the first time researchers observed this phenomena and they are not sure how the chemical enters the frog’s system.

“Our team has not yet conducted a survey of possible nicotine containing in the area where the nicotine-frog was found, and none of our team’s insect samples yielded nicotine in chemical analyses,” Clark said. “However, this is some of the most convincing evidence that plant-insect-frog toxin food chains do exist.”

Other characteristics the Madagascan frogs share with their South American cousins include terrestrial eggs, small body size, and toothless jaws.

Scientists have long known that frogs rely on a diet of ants, beetles, and millipedes to produce their poison. When poison frogs are captured and kept in captivity, they retain skin alkaloids for years.

But they can’t make more without eating the right types of ants. Frogs kept in captivity and fed a steady diet of flies, for example, don’t secrete alkaloids.

This research is detailed in an upcoming issue of the journal Proceedings of the National Academy of Sciences.

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Lol, and this semi related article got a couple chuckles out of me.
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Shrieking Frogs Unnerve Hawaiian Island
By B.J. REYES
Associated Press Writer
posted: 19 January, 2005
4:30 p.m. ET

http://www.livescience.com/animalworld/ ... 50119.html

HONOLULU (AP) _ A tiny frog with a huge shriek has invaded the Big Island and won't shut up.

Mayor Harry Kim is looking for $2 million to begin controlling the spread of the nocturnal coqui frog, a beloved native in Puerto Rico but considered an annoying pest in Hawaii since hitching a ride over in shipments of tropical plants around 1990.

The frogs have been mating easily _ and shattering quiet island nights _ ever since.

Aside from the noise, the frogs have a voracious appetite for spiders and insects, competing with native birds and fauna. And coqui frogs are adaptable to many ecosystems and breed heavily in Hawaii, experts said.

Kim said the Big Island, the local name for the island of Hawaii, will once again ask Gov. Linda Lingle to declare the coqui frog infestation a state emergency to help clear the way for state financial assistance. The $2 million is needed to launch a combined state, federal and county program to combat the frogs, Kim said. He made his plea Tuesday before state lawmakers, who will consider the request later this year.

Kim said he declared a county emergency in April over the frogs, but the state waited to see if the federal government would offer assistance, which it did not.

Spraying of a citric acid solution on the islands of Oahu and Kauai have curtailed coqui populations there, but limited spraying on Kim's island has done little.

``I think the response from all of us has not been timely enough,'' he said, noting that experts suggest he focus on controlling the coqui's spread, rather than eradicating it completely.

``I kick myself in the back every day for not getting started more aggressively,'' Kim said.

More than 150 communities on the Big Island are now infested with the coin-sized frogs, named after their high-decibel ``ko-KEE, ko-KEE'' chirp

What blows my mind is that in both cases it is ants and frogs.
Seems unlikely that this is pure coincidence. I can grasp the idea of evolution converging on the same principle, but with the same organisms? I feel there must be a link between these two cases.
That is just my initial opinion, and in the case of evolution these initial thoughts are often mistaken.

Maybe this could be explained as one of those raining frog scenarios.