Hi Sarah,
You might just try putting them in weakish ethanol. About 50% with water should do it; this will keep the periostracum wet and pliable, and the ethanol will prevent any bacterial action from rotting it. Our standard storage medium here is 80%, but this might not be kind to ancient, waterlogged periostracal cells.
Regards,
PC.
Paul Callomon
Collections Manager
Malacology, Invertebrate Paleontology and General Invertebrates
Department of Malacology
Academy of Natural Sciences
1900 Parkway, Philadelphia PA 19103-1195, USA
Tel 215-405-5096
Fax 215-299-1170
Secretary, American Malacological Society
On the web at http://erato.acnatsci.org/ams/
>>> [log in to unmask] 11/18/05 06:07PM >>>
I recently found some Astarte/Tridonta (mostly A. elliptica) shells which
are almost certainly subfossil dating from the last ice age, but in almost
perfect condition, complete with periostracum. I allowed the first one I
found (unfortunately the only A. borealis) to dry out, and the periostracum
flaked off immediately, as soon as the shell was dry. I have kept the
subsequent finds in the clay and brackish water in which I found them, and
would like to know the best way of preserving these, bearing in mind that
they are probably subfossil and I particularly want to preserve the
periostracum.
I have been advised by a leading expert in ice-age molluscs in the UK where
I live that the best preservation method is to use gum tragacanth as it is
water-soluble and can easily be removed at a later date. He has had great
success with this. But as I have a number of shells, I would also like to
know of any alternatives that I could try so that I am not relying on one
method.
I know this has been discussed before (particularly in April 2002 under the
subject of "oiling shells"), and from what I have read, parafin seems to be
the best bet for preserving periostracum, though I do not really want to
introduce any foreign substance if it is not completely necessary,
particularly in case they were to be subsequently used for research or as
museum exhibits. If I use parafin, would the shells need to be completely
dry first? I doubt if the periostracum would survive complete drying.
The shells have somehow been preserved buried in clay for thousands of
years, and possibly more recently in brackish water, and I am wondering if
there is some way of replicating this natural method of preservation for at
least a short period of time. Would keeping the shells immersed in saline
solution (in glass or plastic tubes so they could still be seen) preserve
the periostracum?
Sarah Longrigg
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