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Re: Haversian systems in lizards
>>> I know I've asked this before, and someone must have responded, and
I lost the response, and men wept openly, but could someone please send me
the reference for the paper where they ran lizards on readmills and found
that they developed Haversian canals?
Thanks. Let's hope this sort of tragedy may be avoided in the
I'm a couple of days late, so I'm assuming that someone has already posted
the reference for the treadmill lizard stuff. So instead I wanted to list
a couple of caveats I have about that paper.
Haversian systems are a primary form of secondary remodelling. One
of the main purposes of secondary remodelling is to shore up the bone
against microfractures that result from excercise. So lets see; Okerwicz
(sic?) howed that animals that were forced to excercise an equal amount
had equal amounts of haversian systems present...not exactly earth
shattering, is it? What was missed is that in the study the
poikilothermic critters were kept in an environment that was constant (I
believe in the 80's F), and all the animals were given the same amount of
food. Since the mammals would have starved if they weren't given enough
food, it's a pretty good bet that the lizards were given as much as an
equal sized mammal would weigh, not the other way around. This was done
in the name of a "controlled" experiment. What it really did was put the
poikilotherms in an unatural environment. Their body temperatures were
raised to a level where their enzymes could act just as efficiently as a
mammals. Then they were forced to excorsize as much as the mammals, and
finally they were given as much to eat as a mammal would need. I,
personally, would have been shocked if the results of the test had turned
out any other way, since the lizards were made into honorary mammals fo
the duration of the test. This test still fails to show that ectotherms
under NATURAL CONDITIONS can produce large amounts of haversian systems.
Also, animals that have parts of their noses cut out are obviously going
to lose more water than those with their noses intact.