There are giants and dwarfs in many cowries. I remember reading a diagram of
size-ranges in many Cypraea spp. (by the Schilders?) in the journal Veliger
long time ago. It is common to see, even within the same population, that
the largest individuals are more than twice as large in shell length as the
smallest. I found a remarkably small-sized C. annulus population on a reef
in Western Samoa (mean size was about 10 mm length), but they just looked
same as larger ones. Both intra- and inter-population size variation, and
also geographical size-clines are evident in this species (and such a
phenomenon may be common among many other cowries). The growth of cowries is
determinate and they do not increase in length (but thicken at both sides of
basal part and along top-inner surface) once they transformed into their
characteristic adult structures. I am curious to find out the genetics of
this individual size variation (there must be some kind of switch to turn
off growing as juveniles but what may be the trigger to become adults?).
Natural selection is slack in this case (clutch-size of cowries depends on
mother's size as she sits on her egg masses to brood underneath until
hatching out, so individual fecundity varies extensively).
Masashi Yamaguchi

-----Original Message-----
From:   [log in to unmask] [SMTP:[log in to unmask]]
Sent:   Wednesday, February 02, 2000 1:36 PM
To:     [log in to unmask]
Subject:        Re: Cypraea tigris vs. schilderiana

Some of our Cypraeaologists may disagree with me, and if so I'll be
interested to hear it, but as far as I know there are no differences in
shell
or soft parts between "typical" Cypraea tigris and the "form" Cypraea
tigris
schilderiana.  The only difference is that Cypraea tigris tends to grow
larger in Hawaii, and it is those large Hawaiian specimens that got tagged
with the name "schilderiana".  Since size alone is not a valid criterion
for
taxonomic separation, I personally think the name schilderiana should be
declared invalid.  And if size is accepted as a criterion, what is the
cutoff?  Is a 120 mm Cypraea tigris from the Philippines a "schilderiana"?
If not, then it would seem that geography, rather than any characteristic
of
the animal is really the deciding factor, and that would be strange
indeed!
While I am on this kick, I feel the same way about the South African
"Cypraea
arabica immanis".  Why can't we just say that Cypraea arabica grows bigger
in
South Africa?  Why does it have to have a different name?
Paul M.