Nora:
   One of my friends found several Cumberlandia monodonta (spectaclecase
mussel), of the Family Margaritiferidae, Order Unionoida  (slightly more
primative than unionids),  frozen in blocks of ice at the edge of the
Mississippi River in Illinois.  He figured they were dead and took them home
to salvage the shells.  To his surprise, the mussels started sticking their
foot out after the ice melted.  I have no idea of how this can occur, and
offhand have never seen anything about this in the literature.  So apparently
some unionids and margaritiferids are hardier, or more adaptable to extreme
conditions than we usually think.  What exactly did you find frozen?
Marian E Havlik
Malacological Consultants
1603 Mississippi Street
La Crosse, Wisconsin 54601-4969 USA
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Phone/Fax: 608.782.7958