Very interesting cowrie thread that Ross started, but for the benefit us newbies
(or maybe just me)- what is rostration?
 
Lynn Scheu wrote:
 
> What a good job you did at covering the abnormal cowries, Wes. That book is
> super. Some of the shells illustrated are amazing. I've always thought
> freak shells were, well, freaky!  That is, until I met the "Porcelaines
> Mysterieuses de Nouvelle Caledonie" by Pierson and Pierson. Wow!  (BTW,
> remember "porcelaines" means "little pigs," whence we derive our word for
> "porcelain".)
>
>  To what you said, Wes, I have other points to add and questions that have
> occurred to me in observing a lot of these shells.
>
> 1. There are also melanistic cowries off Queensland, especially Tryon
> Island. Is there any geologic peculiarity or metal or pollution in the
> water there? What other localities do people have melanistic cowries from?
> C. tigris gets a big black blotch in a certain area in the Philippines, I
> believe.
>
> 2. I understand that nickel mines are one of the suspicious factors in New
> Caledonia.
>
> 3. Rust on wrecks causes dark, rusty red shells in some of the Cyp. lynx
> and arabica and pantherina, etc  in the northwestern Indian Ocean and Red
> Sea as well, I think. Isn't this akin to "melanism" in the sense that it is
> excessive deposit of a pigment, though a different pigment than melanin?
>
> 4. Note that not all oddities from New Caledonia are melanistic. Rostration
> has been mentioned as another effect of whatever the factor is in New
> Caledonia. And rostration is also to be seen in shells from off Tryon Is.
> Q'ld. Also, I have seen a New Caledonia Cyp moneta which was quite heavily
> rostrate and had an intense deep yellow stripe down its back. The rest of
> the shell was white. This is an intensification of the yellow pigment just
> as melanism is an intensification of the black one. But a localized
> intensification, not over the entire shell.
>
> 5. Most of the really rostrate and/or melanistic specimens I have seen are
> very heavy shells for their size. And it has already been stated that none
> of the affected shells are juveniles. Could it be possible that these are
> all very mature shells and that the rostration and melanism or
> intensification of other pigments are the effects of some external factor
> like metals in the water, in combination with age. Age is the factor I am
> aware of in senile Strombus gigas, the ones Clench named Strombus samba.
> They develop a very heavy shell with aperture narrowed by shelly material,
> and the aperture gets an aluminum-like glaze ? Also it seems to me that it
> would take some doing -- energy and resources and time -- to produce some
> of those "Napoleon's Hat" rostrate Cypraea stolida one sees at fantastic
> prices! (Plus more energy and resources to drag it around!) Are there a lot
> of unaffected but otherwise elderly cowries in the Prony Bay area of New
> Caledonia?
>
> 6. I don't know a lot about the concept or content of pigments.  Is this
> phenomenon of darkening in cowries always melanism, a laying down of the
> pigment melanin which I believe is dark or plain black?  Or can it be an
> excess of red pigment? Or just an excess of pigment? The dictionary would
> seem to indicate the latter, yet my Brittanica says it is black pigment.
> Cyp. cribraria forms its very familiar normal pattern of red pigment. But
> it appears, when one observes a series of such shells in all degrees of
> melanistic development, that the dark shell is dark through the heavy
> deposition of red pigment, not black. And so the abnormal New Caledonia  C.
> cribraria shell is not truly "melanistic," as I would understand the term.
>
> Whoa!  I didn't mean to get to 6!
>
> Ross asked why this tendency toward deformity of pattern and shape is the
> case with cowries more so than other shells. I would say that, aside from
> localized melanism and rostration, thay are not.  But cowries are so smooth
> and glossy, often regular and specific of pattern, and smoothly and
> regularly rounded in shape, that deformities are just more evident.
>
> Also the incurving of the outer lip at maturity is going to accentuate any
> injury the animal sustains at that point in its development from bulla to
> adult. And bites out of the mantle are exaggerated hugely in any animal
> that keeps polishing its shell and adding to its pattern the way cowries do.
>
>  Then maybe, given the resourcefulness at escape and cone-foiling, and the
> clever maneuverability we have witnessed second hand in Don's aquarium,
> many cowries live through attacks that would end fatally in other less
> resourceful groups. (I'm pulling for your C. lynx, Helmut! )
>
> Lynn Scheu
> [log in to unmask]
> Louisville, KY, home of the best silent auctions COA ever had!  Wait til
> you see all the cowries!  And I KNOW there are some melanistic cypraea in
> the Bid Auction.