Fluid Collections
Contents
Statement of Purpose
These links and documents contain information about best practices for fluid collections relevant to natural history collections.
Introduction
Fluid-preserved specimens may be plants, animals, or minerals (or any part) that are preserved in a liquid storage medium. Most fluid-preserved specimens are invertebrates, reptiles, amphibians, or fish. The most common fluid preservative is alcohol. The purpose of the fluid preservative solution is to stabilize the specimen and prevent it from deteriorating. The preservative solution and the storage container create a protective microenvironment around the specimen. If placed in a good, stable storage environment and maintained well, fluid-preserved specimens should last for hundreds of years. Fluid preservation has the advantage of preserving the entire organism, including all tissues and gut contents. Fluid-preserved specimens can be dissected for anatomical studies. Some specimens can be removed from the preservative and prepared as dry mounts or skeletons. The disadvantage of fluid-preserved specimens is that the preservative chemically alters the tissues of the specimen, most obviously, by causing changes in coloration. Also, most preservatives cause physical changes to tissues, such as shrinkage.
Importance of stable environment for long-term preservation
Unstable storage environment accelerates deterioration
-Warmer temperatures speed up deterioration processes
-An increase of 10°C doubles chemical reactions
-Extraction of lipids and proteins goes faster
-Cooler temperatures condense lipids and promote paraformaldehyde formation
-Fluctuations in the temperature and humidity of the storage environment stress specimens, containers and their seals. Relative humidity is temperature dependant, and even short exposures to relative humidity over 65% can trigger a mold outbreak.
Temperature based expansion of ethanol
- At 20 deg C, ethanol has a coefficient of expansion 40x glass, however water has a coefficient of expansion 8x glass. An increase in temperature causes fluid levels in a jar of ethanol to rise and can result on stress to the lid and seal. Ideally, leave 10% headspace in containers of alcohol-based preservatives.
Contributors
Source Material
Text sourced from Baseline Standards for Fluid Collections, workshop by Dirk Neumann & Julian Carter https://pfc2018.sciencesconf.org/data/program/Workshop_baseline_standards_fluid_collections_part2_Carter.pdf
Links
Consensus Documents
Community Standards
Review Documents
References
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