Yes! That's what I meant. I know that if they "see" they would see sand, mud, and the occasional diver's foot. What I am interested in is the visual accuity of mollusks. Do Cone "see"? Do Olives? Do any of them see more than light and dark, or general shapes?
   In my fish tank, I have a (not quite united) pair of fiddler crabs, They have eye stalks. The male finds a nice high place and brandishes his lovely, shiny, large right pincer like a beacon. I would assume that the female can "see" this from some distance.
   Otherwise: Cincinnati has had a real "frog-strangler" day. Rain turning creeks into bona-fide rivers, noisy storms, flooding, hail, tornado watches. All that good stuff.
    Art
>
> From: "Thomas E. Eichhorst" <[log in to unmask]>
> Date: 2003/05/10 Sat PM 01:57:48 EDT
> To: [log in to unmask]
> Subject: Re: eyes
>
> I haven't a clue, but always an opinion!  I would bet octopus and squid do
> not have optical sensors in their skin as they have very advanced eyes and
> most likely use their eyes for this purpose.  On the other hand, nerites
> have "closed eyes" that probably do not see much more than light and dark
> shapes.  These combined with their other senses, including the optically
> sensitive dark areas on their skin, still leaves them far short of the
> visual acuity of cephalopods.  The difference here is a group of mollusks
> (octopus and squids) that are active hunters with great mobility.  On the
> other hand you have the neritids who are heavily armored grazers that depend
> upon a number of defensive mechanisms that all added up pretty much equal
> "hunker down."  No need for great visual acuity there.
>
> Tom E
>
> > -----Original Message-----
> > From: Conchologists of America List [mailto:[log in to unmask]]On
> > Behalf Of Mountain Blue Designs
> > Sent: Friday, May 09, 2003 4:54 PM
> > To: [log in to unmask]
> > Subject: Re: eyes
> >
> >
> > Is this the same way of seeing that octopus and squid sense colour and
> > respond with changing their own  colour?
> >
> > -----Original Message-----
> > From: Conchologists of America List [mailto:[log in to unmask]]On
> > Behalf Of Thomas E. Eichhorst
> > Sent: Saturday, 10 May 2003 3:41 AM
> > To: [log in to unmask]
> > Subject: Re: eyes
> >
> >
> > Art -
> >
> > Can't say much about all mollusks, but I can say that some
> > gastropods "see"
> > through their skin.  Tests on Nerita picea Recluz, 1841 (an Hawaiian and
> > Johnson Island endemic nerite) demonstrated a response to shadows
> > generated
> > by dark pigmented areas on the dorsal portion of the foot of the animal.
> > These are usually longitudinal, irregular, dark stripes and are found in
> > quite a few gastropods.  In other words, even though the animal
> > has two eyes
> > (which also react to shadows) it also sees with its skin!  The same dermal
> > shadow response has been recorded in Nassarius reticulata (Linnaeus, 1758)
> > and the garden slug Arion ater.
> >
> > Tom E.
>

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