Wednesday, November 3, 2010

Really Big Dragonflies: Oxygen's What Does It

"High Oxygen Levels Spawn Monster Dragonflies"
Wired Science, Wired (November 2, 2010)

"Biologists have grown super-size dragonflies that are 15 percent larger than normal by raising the insects, from start to finish, in chambers emulating Earth's oxygen conditions 300 million years ago.

"The research, presented Nov. 1 at the Geophysical Society of America's annual meeting in Denver, Colorado, provides more support to the idea that big ancient animals and high-oxygen concentrations weren't coincidental. It may also offer an instrument to help gauge Earth's ancient atmospheric conditions.

" 'No one has been successful growing dragonflies under controlled laboratory conditions before, at least to my knowledge,' said paleobiologist John VandenBrooks of Arizona State University, leader of the work. 'This has allowed us to ask the question, "how have oxygen levels through time influenced the evolution of insects?" '

"During the Paleozoic era, around 300 million years ago, huge dragonflies zipped around with wingspans stretching more than two and a half feet, dwarfing modern relatives. Back then, however, the planet’s atmosphere had roughly 50 percent more oxygen than today...."

So far, the scientists have learned that dragonflies and beetles grow faster and get bigger in high-oxygen environments, while cockroaches grow more slowly and don't get bigger. All the insects grow smaller breathing tubes when they grew in a high-oxygen atmosphere. The smaller breathing tubes make sense, since the critters don't need today's big tubes to get oxygen in when there's plenty around - but the scientists don't know why dragonflies and beetles get bigger and cockroaches don't.

For paleontologists and other folks who study what's happened on Earth for the last few billion years, this research is important. If they can correlate oxygen levels with some feature on insects - ones that haven't changed all that much for the last few hundred million years - they'll be able to work out how much oxygen was around, by observing structures like breathing tubes on insects caught in amber.

The Lemming finds that sort of thing fascinating.

Your experience, as I've said before, may vary.

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