Not just for cowry aficionados...

I'd like to share a curiosity I've just encountered
which concerns one of Hawaii's endemic cowries.
Perhaps some of our CONCH-Lers have seen something
like this and/or are willing to share their
thoughts about possible explanations or causes.

************

I have a group of ~1350 Grooved-Tooth cowries with
the following coefficients of correlation to the
groups' averaged lengths (a method I used before
in http://www.cowrys.org/research/hlvteeth.htm ):

For ~1350 Cypraea sulcidentata:
labial teeth correlate to avgd. lengths ------------0.94
columellar teeth correlate to avgd. lengths --------0.96
labial minus col. teeth correlate to avgd. lengths--0.24

Then I separated the fresh-dead/live-collected shells
from the faded, glossless 'beach' shells, making groups
of ~570 and ~780 shells, respectively. The coefficients
of correlation for these two are:

labial minus columellar teeth to avgd. lengths:
    "beach"         "fresh"
      +0.32           +0.95

That is a surprise! Who would guess that a group with
such a close link between the difference of tooth counts
and the averaged lengths of their groups could emerge
from such a group! Their only difference is the time period
in which they grew. Just about every one of these shells
came from Makua. The live-collected shells were taken in
the last twenty to thirty years, while the 'beach' shells,
taken from the 'pockets' (ancient sinkholes) of Makua)
are probably four or more decades old, and some are probably
hundreds of years old.

The question has to be, "What does this say about present
and past conditions at Makua?" In an attempt to find if
this is "normal" among the cowries, I performed this same
routine on my samples of C. helvola and C. fimbriata.
The results highlight the curious nature of what is
seen above in C. sulcidentata.

      ~2700                  ~500
_____helvola________   ____fimbriata_____
ALL->  0.67                  -0.18
beach   /\   fresh      beach  /\    fresh
~2130 shells ~530      ~180  shells  ~330
  0.61        0.61      -0.45        -0.56

So the Indo-pacific species (at least, these two) DON'T
show the trait that C. sulcidentata does. (However, the
emergence, in C. fimbriata, of two relatively well corel-
lated groups from one non-correlated group does suggest
something.)

That, in a very short form, is the puzzle. What's going
on with Hawaii's Grooved-Tooth cowry? Is it VERY sensitive
to its environs while C. helvola & fimbriata (all above
were collected from the Makua/Waianae coast area) are not?
Or..., What?

Aloha,

makuabob (a.k.a. Bob Dayle)

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