CO2 and muscles/bone evolution

Peter Ashby p-ashby at nimr.mrc.ac.uk
Tue Feb 18 11:24:55 EST 1997


In Article <UPMAIL07.199702150340370832 at msn.com>, rcb5 at MSN.COM ("Ronald
Blue") wrote:
>
>The proposal I made that muscles could have evolved into bones 250 million
>years is not supportable for the following reason.
>
>True that high concentrations of calcium will cause muscles to become
>bones.  True that high CO2 levels in the water will reduce CaOH
>from the sea water by the formation of CaCO2.

It is NOT true that high concentrations of calcium will cause muscles to
become bones.  Muscle cells are a terminally differentiated cell type and
once they have differentiated they cannot change cell type.  You might also
consider that muscles have to act upon something, ie bones in vertebrates or
exoskeletons.  A bone without a muscle to move it is not particularly useful
except as defence.  In addition you have failed to suggest a mechanism for
what you are proposing, if I give you the benefit of the doubt and assume
you are proposing that high calcium exerts an evolutionary influence on
turning muscles into bones you have to sugggest a mechanism of action.  It
is not at all clear why calcium would have this effect.  you also don't seem
to realise that organisms are very good at regulating things like calcium
levels in their tissues and an increase in environmental calcium would
simply make it easier for animals with hard tissues to live in certain
enviroments.

>What is the problem is that fish existed 500 million years ago.

And muscles acting on exoskeletons existed long before that.

SNIP

>By the way shrimp put in high CO2 water environment go dormant for
>up to 4 years with no oxygen according to a recent article in the
>New Scientist.

Not that it has anything to do with calcium, you should mention that the
shrimp were brine shrimp naupli, not adults and that these creatures are
specifically adapted to live in high salt environments and resist
dehydration.  This ability is NOT widespread among shrimps.

Peter
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Peter Ashby                             National Institute for Medical Research
Eukaryotic Molecular Genetics           London, England
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