Preservation for Histology: 4% paraformaldehyde (PFA) and 70% ethanol
For many morphological features, especially those observed with histological techniques, it is useful to fix specimens in 4% PFA, followed by storage in 70% ethanol. However, specimens processed in this manner yield little to no successful DNA extraction, PCR, and sequencing.
The following procedure works well to prepare specimens for histological sections used in confocal microscopy and FISH staining.
A) Prepare fixative by first filter-sterilizing seawater; then add PFA for a final concentration of 4%.
B) Incubate specimen in 4% PFA overnight.
C) Transfer specimen to 70% ethanol.
D) Store at 5°C or -20°C.