Hi Jose,
Few years ago, I worked in _Phyllonotus pomum_ and _P. pomum
margaritensis_ reproduction and biology. I observed few (no more
than a couple of specimens) that had a "double operculum." The
operculum located more superficially was partially separated from
that attached to the foot. Both opercula were laying flat-face to
flat-face but they were not parallel to each other. The attachment
between both opercula occurred close to the border of the youngest
sector (on the border that is closer to the centra). The opening was
approximately facing the outer lip. In either case, the superficial
operculum possessed the typical shape and growth lines of the species
operculum. The operculum attached to the foot was not similar to the
superficial one. Thus, my impression (but I did not test for it!) was
that such double feature was accidental. Lack of definition of growth
lines is usually the product of a very fast rate of growth . Partial
separation of the operculum for accidental reasons (e.g., predation
by crabs), and subsequent generation of a new operculum would explain
the attachment of both opercula at the most recently formed sectors.
Papers of Vovelet, during the sixties, and Hunt, during the
seventies, explain the complex formation of opercula. If you are
interested, I can send you a list of literature relative to this
subject.
Cheers,
Rob
Roberto Cipriani
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| From: Jose H. Leal <[log in to unmask]>
| To: [log in to unmask]
| Subject: Re: Double opercula
| Date: Thursday, March 05, 1998 8:18 AM
|
| Art,
|
| According to Nicholas, they were side by side, but separated by at
least
| 1/2 to 3/4 inch. Unfortunately, he did not preserve the whole
animal, which
| would tell more about the exact location of the opercula and any
| abnormalities on the foot itself. The opercula themselves, however,
look
| normal, with all the growth lines in the right places, etc.
|
| At 09:09 AM 3/5/98 -0500, you wrote:
| >Jose
| > If the two opercula are side by side, could the phenomenon be
the
| >result of a break in the original opercula and a mending that
makes
| >it look like two?
| > art
| >
|
______________________________________________________________________
____
| Jose H. Leal, Ph.D.
| Director-The Bailey-Matthews Shell Museum
| Editor-THE NAUTILUS
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