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AZ: MWU Researcher Featured on Smithsonian Channel's "World's Biggest Beasts"

July 14, 2016

by Office of Communications

Giant dragonfly wing fossil
A giant dragonfly wing fossil - Dr. VandenBrooks' research indicates that insects grew to giant sizes due to an oxygen-rich atmosphere.

The next time you see a big bug in your kitchen that sends you scurrying for cover, be glad that you didn't live 300 million years ago.

John VandenBrooks, Ph.D., a Midwestern University faculty researcher, focuses on insects and their evolutionary development, and he says that insects on Earth used to be far larger than their descendants today. "While we generally think of insects as being small, that wasn't always the case.  300 million years ago, there were griffenflies (an ancestor of modern day dragonflies) with three-foot wingspans flying the skies and 6 foot long millipede-like creatures (Arthropleura) roaming the earth," he says.

Dr. VandenBrooks' research is featured in a new Smithsonian Channel documentary program, "World's Biggest Beasts" (see below for airtimes). He theorizes that the super-sized insects from so long ago achieved their enormous size because of atmospheric differences. "One major difference between when these giant insects existed and today is that there was 50% more oxygen in the atmosphere in the past," he observes.  "This leads to the intriguing hypothesis that more oxygen allowed for the evolution of these giants."  

To understand how oxygen may have allowed insects to achieve these huge proportions, Dr. VandenBrooks rears modern insects in the lab to look at how oxygen affects their growth, development, and respiratory systems, and uses this information to interpret changes in body size seen in the fossil record.  "It turns out that insects reared under lower oxygen levels are smaller and some insects reared under higher oxygen levels do get larger including dragonflies and Madagascar hissing cockroaches.  Exactly how oxygen limits their size still remains a question."

One possibility is that as insects get larger, a greater proportion of their body is taken up with a series of hollow tubes known as tracheae that deliver oxygen to all the cells of an insect.  Eventually, an insect cannot fit any more of these tubes in their body, limiting how big they can be.  Dr. VandenBrooks images these tracheae in modern and fossil insects using fluorescent confocal microscopy and x-ray synchrotron imaging.  Using these methods, he has shown that insects reared in higher oxygen levels reduce the number and size of these tubes, which could allow them to achieve larger sizes, possibly even the gigantic sizes seen in the fossil record.  

"World's Biggest Beasts" airs on the Smithsonian Channel on the following dates:

Check with your cable or satellite TV provider for channel information. Visit the Smithsonian Channel website for more information about the program.

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