Hi Paul and everyone,

I do know that hermit crabs regularly inhabit nerites in my area.  They are all
very small crabs, but seem to be the normal variety that grows larger and moves
on to larger shells. I think they get desperate and use whatever is available.
In our area we have an abundance of nerites on the seawalls near the beaches.
They also use many nonshell homes.  My husband has a cute  photo he took of a
hermit crab in a smirnoff bottle cap.

Karen
--- Paul Monfils <[log in to unmask]> wrote:
> Hi Kath,
>
> No vindication necessary! - this is just an exchange of ideas :-)  Hope
> you didn't feel attacked!
> I guess my problem is that I can't see the adaptive advantage of
> expending all the energy required to enlarge the interior of a shell,
> when it would be so much simpler, and so much more energy efficient, to
> just switch to a larger shell - especially considering that the switch
> is inevitable, and the only thing accomplished by enlargement would be a
> short postponement of the event.  The crab would essentially be
> enlarging the shell in preparation for abandoning it, rather than
> inhabiting it.
> The type of damage you propose must surely be a very slow process,
> whether produced by chemical or physical action, especially on something
> as solid as a nerite shell!  If such action does occur, it seems it
> would have to be chemical in nature, as the chitinous exoskeleton of a
> crustacean is much softer than the shell of a nerite or other gastropod,
> and probably could not scratch the shell, much less physically grind
> away an appreciable part of it.  Given how slow such a process must be,
> I can't imagine that a hermit crab lives in any one shell long enough to
> produce much cumulative damage.  (Is there any data on how long a crab
> inhabits one shell, on the average?)
> You mentioned that the type of aperture damage you observe "seems an
> unlikely wear pattern in relation to beachrolling and other intertidal
> action".  Perhaps this could be tested by putting some nerite (or other)
> shells in a mineral tumbler along with water and sand?
> Another question, for my own information - do hermit crabs regularly use
> nerite shells?  It seems like nerites don't have much of an inner spiral
> to them?  Are there by any chance specific hermit crabs which are
> specially adapted to inhabit nerites?
>
> Regards,
> Paul M.


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