[Odonata-l] help with info

[Nick and Ailsa Donnelly]

I believe oxygen could not be the correct answer.  Numerous scaling
observations relating body mass to oxygen consumption shows that the modest
increase in oxygen that possibly existed during the Permian (when all the
Caroniferous coal beds were buried and not yet exhumed) would have only
increased size by a rather small amount - certainly not 4X linear dimensions
(which is 64X body mass).  
 
More probably the question has always been asked incorrectly.  The question
assumes that the size of modern dragonfies is limited by oxygen partial
pressure.  I believe they are limited by predation pressure combined with
the increased demands for food to support the life style of nearly constant
flying.  During the Permian predators were few, and, until the rise of the
giant amphibians in the late Permian, would not have limited anything.  And
we don't know the dragonfly's life style.  Did they fly only briefly and
then have to rest for a while to recover?  I guess we should regard the
observation of large Permian dragonflies as evidence for extremely low
predation pressure and sufficient available food (other insects).
 
I also seem to recall that metabolic experiments involving grasshoppers
showed that they had more than sufficient capacity for oxidizing muscle
metabolites during  the exercise of tethered flight.
 
Once efficient predators evolved, there was no place for large insects and
they had to abandon large size - where they remain to this day.  By the way,
there were also large insects in other orders, such as orthopteroids.  There
were also lots of small insects in the Permian.
 
Nick Donnelly

  _____  

From: odonata-l-bounces at listhost.ups.edu
[mailto:odonata-l-bounces at listhost.ups.edu] On Behalf Of
iodonata at bellsouth.net
Sent: Thursday, July 10, 2008 8:32 PM
To: TTEAGNOLA at aol.com
Cc: Odonata-l discussion
Subject: [Odonata-l] help with info



Hi group:

 

The second question opens up some discussion which has not been covered here
as far as I can remember.

 

See if you can help

 

Thanks.

 

Bill Mauffray

International Odonata Research Institute

PO Box 147100

Gainesville FL 32614-7100

352-219-3141 cell

iodonata at bellsouth.net

http://www.iodonata.net

 

  _____  

From: TTEAGNOLA at aol.com [mailto:TTEAGNOLA at aol.com] 
Sent: Wednesday, July 09, 2008 7:39 PM
To: iodonata at bellsouth.net
Cc: TTEAGNOLA at aol.com
Subject: Info please

 

 

 

I got your contact information from the Odonata Information Network web
site.

 

http://bellsouthpwp.net/b/i/billmauffray/main.html

 

 

I and my grandsons recently attended the newly opened Audubon Insectarium,
in New Orleans Louisiana.  

 

Near the beginning of the exhibit they have a replica of an ancient giant,
(about 30 inch wingspan) dragonfly / mosquito hawk as it is more commonly
called here. 

 

The information accompanying it asserts that the creature, (then and now)
has relatively inefficient body structures for taking in atmospheric gasses,
meaning oxygen.

 

The supposed reason for the gigantism is that ancient atmospheric levels of
oxygen concentration were much higher than today's levels, allowing the
inefficient respiration system to take in enough oxygen to support large
size.

 

The theory continues that today's much lower oxygen concentrations cannot
support such growth. 

 

I have my doubts about that concept.

 

 

I have two questions for which I am seeking authoritative sources of
information:

 

1. Can these creatures be generationally raised in captivity?

 

2. In an effort to test the question of the oxygen concentration effect on
growth, has anyone ever tried to raise these creatures in captivity to study
the effects of an increased, (artificially) oxygen level concentration
approximating supposed ancient levels?

 

If you can and will answer these questions that would be good. Barring that,
if you could provide some ideas for other likely sources of such
information, that also would be good.

 

 

My name is Mr. Terry Teague. tteagnola at aol.com 

 

 

Thank you for any information you can provide.





  _____  

Get the scoop on last night's hottest shows and the live music scene in your
area - Check  <http://www.tourtracker.com?NCID=aolmus00050000000112> out
TourTracker.com!

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailweb.ups.edu/pipermail/odonata-l/attachments/20080710/0a298ada/attachment-0001.html