Here in south Brazil you can find 3 species of Corbicula in the
same area sometimes. C. fluminea, C. fluminalis and another i
can not remember the name. But most papers identify them only as
C. fluminea.

MARTINS, D. S. ; VEITENHEIMER-MENDES, I. L. V. ;
FACCIONI-HEUSER, M. C. . Corbicula (Bivalvia, Corbiculidae) em
simpatria no lago Guaiba, Rio Grande do Sul, Brasil..
Biociências, Porto Alegre, v. 12, 2005.


regards
Fabio Wiggers


--- "Dr. David Campbell" <[log in to unmask]> escreveu:

> > I was wading in the local creek (central Indiana) when I
> noted a
> > single valve in
> > the foot-deep water. Hoping to stir up its mate, I came up,
> instead,
> > with a
> > live clam. At a mere 3/4-inch across, it was rather
> small,... to
> > someone who
> > has seen three foot wide Tridacna gigas in situ.
> >
> > Since it is illegal in this state to disturb or molest ANY
> mollusk, I
> > tossed it
> > back after noting that the valves were dark brown at the
> hinge but
> > quickly gave
> > way to an algae-green color other the rest of the shell. I
> estimated
> > about 15
> > "growth rings" on it.
> >
>
> Sounds too big for a sphaeriid (fingernail clam).  If the
> "growth
> rings" were regular concentric sculpture, then you had
> Corbicula.
> Despite most of the literature, the main species of Corbicula
> invading
> the U.S. is probably C. leana.  A second species is known only
> from
> the southwest (also invading Europe and South America), which
> may be
> true fluminea (of which manilensis is a synonym).
>
> Unionids may show bands of color or weak irregular growth
> lines, but
> no regular concentric sculpture in our species.
>
> As sculpture rather than growth rings, they form fairly
> quickly and
> without direct connection to environmental factors.  Tiny
> juveniles
> already have several concentric ribs.
>
> Corbicula range from oval (not very elongate) to nearly
> triangular in
> some large old individuals in lakes.  Most unionids are more
> elongate.
>
> --
> Dr. David Campbell
> 425 Scientific Collections Building
> Department of Biological Sciences
> Biodiversity and Systematics
> University of Alabama, Box 870345
> Tuscaloosa AL 35487-0345  USA
>
>
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