[Odonata-l] help with oxygen...

[Ethan Bright]

Further to Nick's answer, recent work on insect respiration and 
physiology (e.g., Westneat et al. 2003, Science 299(5606):558-560) 
suggests insect respiration isn't so passive, so ambient oxygen 
concentration changes during the Permian probably weren't a huge factor. 
Further, the issue isn't just predation on adults; I'm sure that larger 
odonates required longer periods for nymphs to develop. That would have 
made them susceptible not only to fish and immature amphibian predation 
(and probably other arthropod and invertebrate parasites), but also 
probably to the increasingly drier continental conditions (and higher 
salinity?; also higher dissolved oxygen stress?) of the later Permian 
aquatic environments.

Nick and Ailsa Donnelly wrote:
> 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). 
>  
....