"Dragonflies are notoriously difficult to rear," said VandenBrooks. "We are one of the only groups to successfully rear them to adulthood under laboratory conditions."
Once they had worked that out, however, they raised three sets of 75 dragonflies in atmospheres containing 12 percent (the lowest oxygen has been in the past), 21 percent (like modern Earth's atmosphere) and 31 percent oxygen (the highest oxygen has been).
Cockroaches, as anyone who has fought them at home knows, are much easier to rear. That enabled the researchers to raise seven groups of 100 roaches in seven different atmospheres ranging from 12 percent to 40 percent oxygen mimicking the range of paleo-oxygen levels. Cockroaches took about twice as long to develop in high oxygen levels.
"It is the exact opposite of what we expected," said VandenBrooks. One possibility is that the hyperoxic reared roaches stayed in their larval stage longer, perhaps waiting for their environment to change to a lower, maybe less stressful oxygen level.
This surprising result prompted the researchers to take a closer look at the breathing apparatus of roaches their tracheal tubes. These are essentially hollow tubes in an insect's body that allow gaseous oxygen to enter directly into the insect tissues.
VandenBrooks and his team took their hyperoxic reared roaches to Argonne National Lab's x-ray synchrontron imaging facility to get a closer look at the tracheal tubes. The x-ray synchrontron is particularly good at resolving the edges where things of different phases meet like solids on liquids or gas on solids. That's just what the inside of a tracheal tube is.
What they found was that the tracheal tubes of hyperoxic reared roaches were smaller than those in lower oxygen atmosph
|Contact: Christa Stratton|
Geological Society of America