At 4:22 PM 98.4.5 +1000, Andrew Taylor wrote:
>Kooyman makes it clear that Emperor Penguins in their prodigious dives
>must avoid decompression sickness: nitrogen bubbles occuring in tissues
>on ascent.
This makes sense to me - I can't see how any diving animal can avoid the
physical problem of nitrogen partitioning from trapped air at high pressure
into the blood and thence tissues.
If I were a penguin I would want to exhale completely to avoid such
problems amd evolve massive myogolobin stores in my muscles to supply them
with oxygen instead of trying to supply them from air in my lungs.
I would probably want to supply my brain in a similar manner from special
myoglobin stores, then I could control oxygen levels on ascent too and
avoid Shallow Water Blackout. I would need my muscles to tolerate high
bicarbonate or lactic acid levels until I could flush them and recharge at
the surface. I would be able to shut down the blood supply to most of the
body as a result, and my heart rate could drop substantially and I could
save energy.
The high pressure during the dive would squash the air in the insulation of
my feathers, and being rather small I could probably not rely on a thick
layer of fat for insulation as it would take up a proportionately too large
part of my body volume and make me too buoyant, so it would be better if I
could tolerate a considerable decrease in my body temperature. Since I
wouldn't need to supply oxygenated blood to my muscles during the dive this
would be no problem but when I surface I will need to increase the blood
flow dramatically: this would lead to a nasty drop in blood temperature to
my brain unless I evolved some countercurrent system to keep it insulated
from this effect. (This is assuming that i asm not always swimming so hard
after fish that the metabolism of my muscles keeps them at normal body
temperatrue which I would not want to have to rely on...)
>
>How Emperor Penguins cope with any of these problems is, as far as I know,
>unknown.
No references - I'm guessing. If I could I would evolve evertible gills
which I could store under my feathers to stop them freezing up out of the
water...
Des Allen
Tokyo
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