On Thu, 2 Apr 1998, Julie Raines wrote:
> This made me wonder about my statements on Nitrogen Narcosis and Oxygen
> Toxicity. I consulted my old animal physiology book which stated "Diving
> animals are not subject to the dangers of oxygen toxicity or the narcotic
> effects of inert gases for the simple reason that they do not breath a
> continuous supply of air during the dive".
I really commend Kooyman's book "Diverse Divers" [1] for anyone who
wants to understand the adaptions that penguins and other air-breathing
vertebrate divers require. I haven't another book which covers this
well and misconceptions are common, including apparently in Julie's old
physiology text. A good uni library should carry his book. Kooyman also
did the field work observing the 500+m dives in Emperor penguins [2].
Kooyman makes it clear that Emperor Penguins in their prodigious dives
must avoid decompression sickness: nitrogen bubbles occuring in tissues
on ascent.
They also must avoid nitrogen narcosis: narcotic effects of high partial
pressures of nitrogen affecting the brain. This affects scuba divers
below 30m.
And they also may have to avoid High Pressure Nervous Syndrome (NPNS):
various effects on the nervous system includes uncontrollable tremors.
Human experience these below 200m. The causes are (last I heard)
uncertain but maybe associated with helium.
Oxygen toxicity is not a problem for penguins or any other air-breathing
vertebrate diver according to Kooyman (excluding humans with scuba tanks).
However Emperor Penguins must deal the converse problem, Shallow Water
Blackout: ascent producing low levels of oxygen.
How Emperor Penguins cope with any of these problems is, as far as I know,
unknown. I'm definitely not saying these are the only problems Emperor
Penguins face. Interestingly, Kooyman notes in [2] that aerobic
considerations suggest Emperor Penguins may be capable of 800m dives!
Andrew Taylor
[1] Diverse divers : physiology and behavior, G L. Kooyman,
Springer-Verlag, 1989
[2] Diving behavior of emperor penguins nurturing chicks at Coulman
Island, Antarctica, G L. Kooyman, Condor 97:536-549.
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