Allen, et al.,

It is most likely a case of the genetic variability being present, "waiting"
for an appropriate chemical stimulus to induce its expression. The evidence
is that individuals of several Nucella species have been shown
experimentally to grow thicker shells (and I think narrower apertures too)
when they are exposed to water that crabs have previously occupied.

Alan

----- Original Message -----
From: "Allen Aigen" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, March 25, 2009 6:59 AM
Subject: [CONCH-L] Crab Induced Snail Evolution in Our Generation?


> The New York Times Science section(March 24)has a short note: Hidden in
> Plain Sight, a Bigger Shell on a Snail Facing a New Predator.  Jonathon
> A.D. Fisher, Queens University, Ontario, Peter S. Petraitis, University of
> Pennsylvania et al, in the Proceedings of the National Academy of
> Sciences, reported that Nucella lapillus (Atlantic Dogwinkle, an
> intertidal muricid) on Mount Desert Island, Maine, increased in length by
> about 23% since collections made in 1915-1923.  This is reported to be an
> apparent result of adaptation to the introduced crab Carcinus maenus which
> preys on the smaller specimens.  Therer is no indication in the article if
> there was a change in the genetics of the snail or if the variability was
> part of the genotype, waiting for a need to be expressed.
>
> Allen Aigen
> [log in to unmask]
>
> ----------------------------------------------------------------------
> [log in to unmask] - a forum for informal discussions on molluscs
> To leave this list, click on the following web link:
> http://listserv.uga.edu/cgi-bin/wa?SUBED1=conch-l&A=1
> Type your email address and name in the appropriate box and
> click leave the list.
> ----------------------------------------------------------------------
>

----------------------------------------------------------------------
[log in to unmask] - a forum for informal discussions on molluscs
To leave this list, click on the following web link:
http://listserv.uga.edu/cgi-bin/wa?SUBED1=conch-l&A=1
Type your email address and name in the appropriate box and
click leave the list.
----------------------------------------------------------------------