Hail fellow Coneheads,
Two possibly contradictory reasons have been mentioned dealing with
high-coned limpets' water. One is that water should evaporate to produce
cooling. The other is that water must be retained to prevent desiccation.
That's an interesting point about the skirt and the muscle.
Has there been observation on what limpets do with their water?
--David
>Hi
>It's great that an in-depth discussion on a scientific point arises on
>occasion. I'm surprised nobody challenged my 'classic ecological
>interpretation'. It so happens I have data from the Med that shows more
>planar forms higher up. And more conical ones lower down. But this fact
>can
>be explained by two things: (1) there is longitudinal migration (mostly
>temporary, but sometimes permanent) of individuals. So you need to look
>at
>your population at different times of the day (and night). (2) How well
>can
>you determine the variations in wave impact over the intertidal over a
>set
>period?
>
>It was discovered many years ago (early this century) that limpets
>living
>higher up the shore do indeed have more conical shells. This is
>intuitively
>wrong (as the thoughts of the students in the survey mentioned earlier
>on
>the list attest to). You would expect the flatter ones higher up (which
>does
>sometimes happens and which can be explained, possibly, by what I had
>mentioned in my last posting). However, in this case, physiology and
>simple
>mechanics supersede ecological explanations. As a result of increased
>exposure higher up the shore the individuals living there need to
>maintain a
>tighter seal between shell periphery and substratum, to avoid
>desiccation.
>Those further down don't have this constraint. What does this cause? The
>
>increased use of the powerful muscles, acting over considerable periods,
>
>actually displaces the mantle skirt (which produces the shell). This
>results
>in a displacement of lower diameter. The shell continues to grow- but
>more
>upwards! So, you get a higher cone. Those of us who dive may have seen
>limpets living in the intertidal that are well over twice the size of
>their
>intertidal brothers (increased feeding opportunities) and very planar
>(zero
>desiccation).
>
>Sometimes you see a type of ringing effect on the shell. There are
>circular
>ridges. Tagging has shown this may result from movement of individuals
>from
>lower to higher ( and vice versa) areas of the intertidal with
>consequent
>compensatory use of the muscles and varying mantle skirt diameters.
>
>The effects of storm surge etc. have also been recently demonstrated for
>the
>freshwater genus Melanopsis. Shell morphology follows similar patterns
>to
>those of limpets in relation to thickening, periphery diameter etc. So
>this
>is a really interesting area of research for anyone who has the time (a
>good
>PhD topic here).
>
>Next time you contemplate the intertidal, don't look for the accepted
>patterns of exposure etc. etc. that is classic textbook. Often the
>animals
>and plants there can tell you what is happening. All of us must have
>seen
>'lower shore' species high on the intertidal where a micro-pool has
>developed. Look at the limpets, for example, in the opposite way to
>which
>you might think. Flatter forms higher up might show that, on this
>particular
>rock face, maybe because of a localized sheltering effect, the exposure
>levels may be lower. And higher coned individuals lower down may show
>that
>there is extreme exposure at times you've not visited the site and seen
>that, again, because of a localized effect, this particular rock face
>has
>much more intense exposure.
>
>Nature is so exciting. Always try and look for new patterns and ways of
>interpreting things.
>
>Alex
>
><!doctype html public "-//w3c//dtd html 4.0 transitional//en">
><html>
><font face="Arial,Helvetica"><font size=-1>Hi</font></font>
><br><font face="Arial,Helvetica"><font size=-1>It's great that an in-depth
>discussion on a scientific point arises on</font></font>
><br><font face="Arial,Helvetica"><font size=-1>occasion. I'm surprised
>nobody challenged my 'classic ecological</font></font>
><br><font face="Arial,Helvetica"><font size=-1>interpretation'. It so happens
>I have data from the Med that shows more</font></font>
><br><font face="Arial,Helvetica"><font size=-1>planar forms higher up.
>And more conical ones lower down. But this fact can</font></font>
><br><font face="Arial,Helvetica"><font size=-1>be explained by two things:
>(1) there is longitudinal migration (mostly</font></font>
><br><font face="Arial,Helvetica"><font size=-1>temporary, but sometimes
>permanent) of individuals. So you need to look at</font></font>
><br><font face="Arial,Helvetica"><font size=-1>your population at different
>times of the day (and night). (2) How well can</font></font>
><br><font face="Arial,Helvetica"><font size=-1>you determine the variations
>in wave impact over the intertidal over a set</font></font>
><br><font face="Arial,Helvetica"><font size=-1>period?</font></font><font
>face="Arial,Helvetica"><font size=-1></font></font>
><p><font face="Arial,Helvetica"><font size=-1>It was discovered many years
>ago (early this century) that limpets living</font></font>
><br><font face="Arial,Helvetica"><font size=-1>higher up the shore do indeed
>have more conical shells. This is intuitively</font></font>
><br><font face="Arial,Helvetica"><font size=-1>wrong (as the thoughts of
>the students in the survey mentioned earlier on</font></font>
><br><font face="Arial,Helvetica"><font size=-1>the list attest to). You
>would expect the flatter ones higher up (which does</font></font>
><br><font face="Arial,Helvetica"><font size=-1>sometimes happens and which
>can be explained, possibly, by what I had</font></font>
><br><font face="Arial,Helvetica"><font size=-1>mentioned in my last posting).
>However, in this case, physiology and simple</font></font>
><br><font face="Arial,Helvetica"><font size=-1>mechanics supersede ecological
>explanations. As a result of increased</font></font>
><br><font face="Arial,Helvetica"><font size=-1>exposure higher up the shore
>the individuals living there need to maintain a</font></font>
><br><font face="Arial,Helvetica"><font size=-1>tighter seal between shell
>periphery and substratum, to avoid desiccation.</font></font>
><br><font face="Arial,Helvetica"><font size=-1>Those further down don't
>have this constraint. What does this cause? The</font></font>
><br><font face="Arial,Helvetica"><font size=-1>increased use of the powerful
>muscles, acting over considerable periods,</font></font>
><br><font face="Arial,Helvetica"><font size=-1>actually displaces the mantle
>skirt (which produces the shell). This results</font></font>
><br><font face="Arial,Helvetica"><font size=-1>in a displacement of lower
>diameter. The shell continues to grow- but more</font></font>
><br><font face="Arial,Helvetica"><font size=-1>upwards! So, you get a higher
>cone. Those of us who dive may have seen</font></font>
><br><font face="Arial,Helvetica"><font size=-1>limpets living in the intertidal
>that are well over twice the size of their</font></font>
><br><font face="Arial,Helvetica"><font size=-1>intertidal brothers (increased
>feeding opportunities) and very planar (zero</font></font>
><br><font face="Arial,Helvetica"><font
>size=-1>desiccation).</font></font><font face="Arial,Helvetica"><font
>size=-1></font></font>
><p><font face="Arial,Helvetica"><font size=-1>Sometimes you see a type
>of ringing effect on the shell. There are circular</font></font>
><br><font face="Arial,Helvetica"><font size=-1>ridges. Tagging has shown
>this may result from movement of individuals from</font></font>
><br><font face="Arial,Helvetica"><font size=-1>lower to higher ( and vice
>versa) areas of the intertidal with consequent</font></font>
><br><font face="Arial,Helvetica"><font size=-1>compensatory use of the
>muscles and varying mantle skirt diameters.</font></font><font
>face="Arial,Helvetica"><font size=-1></font></font>
><p><font face="Arial,Helvetica"><font size=-1>The effects of storm surge
>etc. have also been recently demonstrated for the</font></font>
><br><font face="Arial,Helvetica"><font size=-1>freshwater genus Melanopsis.
>Shell morphology follows similar patterns to</font></font>
><br><font face="Arial,Helvetica"><font size=-1>those of limpets in relation
>to thickening, periphery diameter etc. So this</font></font>
><br><font face="Arial,Helvetica"><font size=-1>is a really interesting
>area of research for anyone who has the time (a good</font></font>
><br><font face="Arial,Helvetica"><font size=-1>PhD topic
>here).</font></font><font face="Arial,Helvetica"><font
>size=-1></font></font>
><p><font face="Arial,Helvetica"><font size=-1>Next time you contemplate
>the intertidal, don't look for the accepted</font></font>
><br><font face="Arial,Helvetica"><font size=-1>patterns of exposure etc.
>etc. that is classic textbook. Often the animals</font></font>
><br><font face="Arial,Helvetica"><font size=-1>and plants there can tell
>you what is happening. All of us must have seen</font></font>
><br><font face="Arial,Helvetica"><font size=-1>'lower shore' species high
>on the intertidal where a micro-pool has</font></font>
><br><font face="Arial,Helvetica"><font size=-1>developed. Look at the limpets,
>for example, in the opposite way to which</font></font>
><br><font face="Arial,Helvetica"><font size=-1>you might think. Flatter
>forms higher up might show that, on this particular</font></font>
><br><font face="Arial,Helvetica"><font size=-1>rock face, maybe because
>of a localized sheltering effect, the exposure</font></font>
><br><font face="Arial,Helvetica"><font size=-1>levels may be lower. And
>higher coned individuals lower down may show that</font></font>
><br><font face="Arial,Helvetica"><font size=-1>there is extreme exposure
>at times you've not visited the site and seen</font></font>
><br><font face="Arial,Helvetica"><font size=-1>that, again, because of
>a localized effect, this particular rock face has</font></font>
><br><font face="Arial,Helvetica"><font size=-1>much more intense
>exposure.</font></font><font face="Arial,Helvetica"><font
>size=-1></font></font>
><p><font face="Arial,Helvetica"><font size=-1>Nature is so exciting. Always
>try and look for new patterns and ways of</font></font>
><br><font face="Arial,Helvetica"><font size=-1>interpreting
>things.</font></font><font face="Arial,Helvetica"><font
>size=-1></font></font>
><p><font face="Arial,Helvetica"><font size=-1>Alex</font></font></html>
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