Sunday, November 7, 2010

"There were giants in the earth in those days"

There is an article from Wired that highlights some research that is (sorta) about insect development. From the article:

To explore the effects of ancient oxygen levels, VandenBrooks’ team raised dragonflies and 11 other “living fossils,” including beetles and cockroaches, in three habitats with different oxygen concentrations — one at the late Paleozoic’s 31 percent oxygen level, another at today’s 21 percent level and the third at 12 percent from 240 million years ago (Earth’s lowest oxygen level since complex life exploded onto the scene half a billion years ago).
They found that dragonflies and beetles grew faster, as well as bigger, in a high-oxygen environment, while cockroaches grew slower and remained the same size. All but two bug species grew smaller than normal at low concentrations of oxygen.
 *Italics added*
This is super neat! A single environmental factor seems to be having substantial effects on the development of these insects.  Oxygen levels seem to be having most of their effect on the tracheal system of these insects, which is what you would expect, since the trachea are the organs that bring oxygen to insect tissues. They also seem to think that they could use tracheal  measurements from insects trapped in amber to determine ancient oxygen levels.
It would be interesting to see if there are developmental reasons why cockroaches don't respond as quickly to increased oxygen. Could the dragonflies' aquatic larvae impact the process? Or might there be genetic factors that create other growth constraints in cockroaches? Would there be similar effects on arthropods that do not have trachea, but have book lungs? It's neat stuff, but the research was presented at a geological meeting, so the developmental questions were not the ones that were most addressed. Also, they said things like this:
dragonflies and other insect groups do develop and evolve larger body sizes in hyperoxia...
They evolve larger body sizes!? Were the changes in body size heritable?  Has the author never heard of Lamarck? This seems wrong, but I don't know any of the details of the research, so frankly I can't make any better of a judgment than that. I hope to see an article about this at some point, because I really want to know more.

The quote in the title is from Genesis 6:4.