Nora,
I remembered this morning that I misstated something: it's not the larger
surface area per se--it's the larger surface to mass ratio. That's the key
to rapid cooling. Evaporative cooling may play a role too. I wonder if
there could be an experiment set up along these lines.

I used to be in a graduate program in biological psychology. One of the
students turned me on to many of the principles of thermoregulation and I
did a lot of library research dealing with a hypothesis of Sudden Infant
Death Syndrome. Anyhow, one of the illustrations of the surface to mass
principle of cooling is how vulnerable newborn mammals are to dying of
hypothermia. Not only do they have high surface to mass ratios but they're
wet!

There! We have both explanations again (radiant and evaporative cooling)!
The threat posed by heat loss in newborns is the reason modern OBGYN
practictioners insist on placing a cap on the newborn's head.

A key factoid here that many non-pediatricians don't recognize is that 90%
of the body's heat is produced by the brain in newborns! (Part of the
reason for the high percentage is that the head is so much larger in
proportion to the rest of the body in newborns).

I wonder if keyhole limpets fare better than non-keyhole limpets. What do
you think? --David

>David
>That is a good point about the cone shape radiating away.  I think the
>effect of
>the water in the cone is still part of it though, as it is a buffer helping to
>lessen the impact of rapid temperature change in either direction.  I may have
>made this up in my head, but I really think I read it somewhere, I don't
>think I
>can take credit!
>
>Nora
>Calgary, Alberta
>(keep forgetting to add this!)
>
>David Kirsh wrote:
>
>> Tall is cool.
>> High cones might be explained by the need to avoid overheating but that is
>> probably not related to space for water (since water, once heated, will
>> retain heat longer).
>> The greater surface area of the high cones will radiate heat away from the
>> limpet more quickly than the squat, compact limpets. There are many
>> examples of this principle in the plant and animal kingdoms, in which there
>> are intuitively unexpected structures in heat-exposed organisms. The
>> stegosaurus' plates may have served this thermoregulatory purpose.
>> -David
>> >Hi all limpet lovers,
>> >This is a very technical question (why and how limpets are more conical at
>> >the higher-energy swash zone than lower on the beach).  I couldn't even
>>begin
>> >to say how but I have heard that it is advantageous to limpets to be more
>> >conical where they are more exposed to protect them from temperature
>> >extremes.  The idea is that the water in the apex of the shell provides a
>> >measure of protection against overheating, and against cooling to a lesser
>> >degree.
>> >I just got back from a week on the west coast (a near first for me) and saw
>> >many, many limpets.  I collected some and and still having fun identifying
>> >them.  I can attest to the stats discovered by our student as the limpets
>> >(still haven't figured out which type) I saw in one bay on rocks right at
>> >high tide were very highly conical, as high as a Whitecap Limpet (Acmaea
>> >mitra).
>> >A good work on natural history of mollusks is "Living Marine Molluscs", by
>> >C.M. Yonge and T.E. Thompson, published in 1976 by Collins, London.
>>This book
>> >has good info on limpets and may also have some more detailed listings
>>in the
>> >bibliography.
>> >
>> >
>> >Lynn Scheu wrote:
>> >
>> >> I have a request for information here below. Can anyone help Anthony?
>> >> Please send your answers to Conch-L or to me personally at
>> >> [log in to unmask]
>> >>
>> >> Thanks for any help,
>> >>
>> >> Lynn Scheu
>> >> Louisville, KY
>> >> [log in to unmask]
>> >>
>> >> > Hi there!
>> >> >          I'm a third year undergraduate here in the UK, my name's
>> >> > Anthony Jones, i'm an environmental science student.  Recently my class
>> >> > took a field trip to a rockyshore habitat, there we examined the shapes
>> >> > of limpets within the intertidal zone, since then several statistical
>> >> > methods have been employed to determine if the shape of the shell
>> >> > varies within the intertidal zone, the results, as previously thougth,
>> >> > confirm that indeed they do.  Limpets being more conical at the high
>> >> > energy swash zone, and more flatter, with a rounder apex and the sub
>> >> > inter tidal zone, this was the reverse of what the students expected,
>> >> > our lecturer however said this was correct, he then set an assignment
>> >> > for us to found out why and how this change is induced, we know it's
>> >> > not genetic, that the change is environmentally induced, but more
>> >> > information is needed, i suspect it have something to do with the
>> >> > attachment mechanism employed by the limpet to attach itself to the
>> >> > substrate, but have failed to come up with any information pertaining
>> >> > to the explanation.  Okay any information or pointers to where i'd be
>> >> > able to find out about this would be much appreciated.
>> >> >
>> >> > Yours
>> >> >
>> >> > Anthony Jones