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Re: Unidirectional gator breathing in Science



Yes. The implications may be quite interesting relative to sauropod lifestyle, 
too.

Observations -- 1) Anhingas have long necks and presumably narrow trachea, yet 
regularly swim w/ their bodies totally submerged, having only their heads and a 
short section of the neck out of the water. 
2) Muscovy ducks and chickens seem to have no trouble breathing even when 
manually held tightly enough to prevent escape or wing flapping.

Speculation -- It may be that birds and other animals w/ an "avian-style" 
respiratory system aren't as vulnerable to breathing problems created by high 
external pressure on the body combined w/ a lower pressure of the air in the 
breathing passages, versus animals w/ a "mammalian-style" system. 

If so -- the famous falsification of the "snorkel-theory" (i.e., sauropods 
using their long necks as snorkels) seems to have tacitly assumed that 
sauropods had a mammalian-style "tidal system", and so the falsification may in 
turn be falsifiable.

I insist that everyone immediately drop everything and test a few birds, and 
maybe an alligator and even an iguana...

--- On Thu, 1/14/10, Andrew Farke <afarke@gmail.com> wrote:

> From: Andrew Farke <afarke@gmail.com>
> Subject: Unidirectional gator breathing in Science
> To: dinosaur@usc.edu
> Date: Thursday, January 14, 2010, 4:55 PM
> Saw this presented at SICB a few
> years ago - super cool stuff!
> 
> Farmer, C.G., and K. Sanders. 2010. Unidirectional airflow
> in the
> lungs of alligators. Science 327(5963):338-340.
> DOI: 10.1126/science.1180219
> 
> The lungs of birds move air in only one direction during
> both
> inspiration and expiration through most of the tubular
> gas-exchanging
> bronchi (parabronchi), whereas in the lungs of mammals and
> presumably
> other vertebrates, air moves tidally into and out of
> terminal
> gas-exchange structures, which are cul-de-sacs.
> Unidirectional flow
> purportedly depends on bellowslike ventilation by air sacs
> and may
> have evolved to meet the high aerobic demands of sustained
> flight.
> Here, we show that air flows unidirectionally through
> parabronchi in
> the lungs of the American alligator, an amphibious
> ectotherm without
> air sacs, which suggests that this pattern dates back to
> the basal
> archosaurs of the Triassic and may have been present in
> their
> nondinosaur descendants (phytosaurs, aetosaurs,
> rauisuchians,
> crocodylomorphs, and pterosaurs) as well as in dinosaurs.
>