An evolutionary prediction

In
http://www.pandasthumb.org/archives/2005/10/pharyngula_an_e.html
I show not only how the work by Marden shows how
insect flight evolved gradually but I also show an
interesting evolutionary prediction which was tested.

    Marden wrote:

    I’m tickled to see that my work on stonefly flight
has come up in this discussion. One thing that is
worth adding here is that a gills-to-wings transition
would require a simultaneous change in gas exchange,
since a sophisticated wing is unlikely to also be an
effective gill, and the physics and physiology of gas
exchange are very different in an aquatic versus a
terrestrial environment. My research shows that modern
stoneflies may have retained intermediate forms of
flight that date back to an evolutionary transition
from gills to wings, and therefore perhaps they have
retained other traits related to a transition in gas
exchange physiology. This line of thinking led me to
suggest to Thorsten Burmester, an expert on arthropod
gas exchange proteins, that he should check to see if
stoneflies have hemocyanin in their blood. This was a
pretty far out idea, since blood-based gas exchange is
what other arthropods use (including aquatic ones) but
was previously thought to be completely absent in
insects, which deliver air directly to their tissues
via tracheae. Burmester found that stoneflies do
indeed have hemocyanin in their blood (Proceedings of
the National Academy of Sciences 101: 871-874) that
reversibly binds oxygen, and it appears that no other
pterygote insects possess this trait. In summary, the
developmental evidence that you have presented for a
gills-to-wings transition is supported by both a set
of mechanically intermediate forms of winged
locomotion in stoneflies and molecular evidence that a
simultaneous transition occurred in gas exchange
physiology.
Received on Sat Oct 29 20:08:41 2005