HI CONCHLERS
Yes diatoms are ALGAE and there is a good list [log in to unmask]
for those interested. Conchlers go back in your shells or teuths?
Peter
----- Original Message -----
From: "Monfils, Paul" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, March 21, 2002 8:30 AM
Subject: Re: Thank you and another question


> I didn't see a question concerning diatoms, but folks seem  to be
responding
> to one??  So here is a little information.  Diatoms are microscopic
> single-celled algae, which have a cell wall composed of silica.  They are
an
> important food source for many browsing types of snails, both in fresh
water
> and marine habitats.  Snails which live on seaweeds for example, like
> Littorina and Lacuna, as well as snails which live on lily pads and other
> fresh water plants, do not usually eat the seaweed or plant itself, but
> rather browse on the diatoms and other unicellular algae which live in the
> slimy secretions on the surface of the larger organism.  The cell wall, or
> "shell" of a diatom is made in two halves which fit together like the top
> and bottom of a friction-fit plastic box, one half overlapping the other.
> The silica walls are inscribed with extremely fine striations, the spacing
> of which is extremely constant in a given species.  The ability to
visually
> distinguish these striations is used as a measure of the resolving power
of
> various microscopes and other optical instruments. In some parts of the
> oceans, the sediment is composed largely of empty diatom shells.  The
silica
> does not biodegrade, and is chemically inert, so they tend to remain
> virtually forever, and are common as fossils.
> Ordinarily, organisms the size of diatoms, which can be readily seen with
a
> standard student microscope, would not be measured in angstroms, but in
> microns (=micrometers).  A micron is one thousandth of a millimeter (or a
> millionth of a meter).  An angstrom is one ten-thousandth of a micron, or
or
> one ten-millionth of a millimeter, a distance which is too small to be
> useful in light microscopy, but which is used in electron microscopy, as
> well as for measuring wavelengths of electromagnetic radiation.
> I hope this relates to the original question, which must have slipped by
me
> somehow.
> To put this in perspective, the world's smallest snail shell, Ammonicera
> rota, measures a whopping 5 MILLION angstroms, while the world's largest
> gastropod, Syrinx aruanus, can reach a length of 7,500,000,000 angstroms!
>
> Regards,
> Paul M.
>