[Coral-List] coral fixation and decal

[goldberg at fiu.edu]

I may as well throw my two cents in on this topic. While 
it is true that there is nothing standard when it comes to 
fixation and decalcification of corals, there is a 
considerable literature on how to decalcify vertebrate 
tissue. It would be a mistake not to consider all of that 
work, depite the differences in mineralization between 
the two systems. Take a look at  Callis et al.,  Journal of 
histotechnology 21: 49-58, 1998 for a review. If you are 
not planning on anything more than standard histology, 
you can do pretty much anything that has been 
suggested. However, if you plan on looking at cell 
structure or tissue relationships, the literature is pretty 
clear that fixation and decalcification methods do 
matter. Unbuffered formalin or strong mineral acids, for 
example, will distort the cytoplasm and cause the loss 
of proteoglycan typical of calcified material (see 
Goldberg, Tissue and Cell 33: 376-387, 2001). For my 
own general work with coral tissues I use a somewhat 
hypertonic medium compared to seawater: 2.5-3% 
glutaraldehyde + 0.15 M NaCl buffered with 0.1 M 
cacodylate to pH 7.6-7.8. For decalcification of small 
specimens I use 2% ascorbic acid (Dietrich & Fontaine, 
Stain Technology 50: 351-354, 1975) or 5%  lactic 
acid/k-lactate buffered to pH 4 for larger chunks (see 
Eggert & Germain, Histochemistry 59: 215-224, 1979).
I will be happy to provide more specifics once I know 
what you are looking for.
best wishes,
wmg

Walter M. Goldberg
Professor of Biological Sciences &
Marine Invertebrate Search Committee Chair
Florida International University
Department of Biological Sciences
University Park
Miami, FL 33199
e-mail goldberg at fiu.edu
URL   www.fiu.edu/~goldberg