Wednesday, 22 September 2010

Microscope mounting media

Currently for work, I'm starting to explore and become familiar with the Springtails (Collembola). They are fascinating little creatures, but are a bit hard to identify with any degree of certainty without mounting them on a microscope slide.

There are a number of different techniques of mounting specimens on a microscope slide. None are the best for all situations though. For quick, temporary mounts, liquids such as Glycerol and Lactic acid can be suitable. For longer-lasting mounts, more complex mixtures usually involving various hazardous substances are used. The Smithsonian Copepod Page and a guide to insect collection curation both give an excellent overview of the longer-term options available for slide mounting specimens, as well as recipes for the various fluids and mixtures. Additionally, the Natural History Museum has a page giving a summary of the results of a mailing list discussion on the subject.

It seems though that the general consensus is that the resin Canada Balsam is THE medium for long-term (i.e. greater than 20 years) mounting of specimens. Despite concerns about requiring Xylene in its preparation, the long time required to make the slides, and concerns that its refractive index is sometimes too high for some specimens, it remains the time-tested solution for microscope mounting of specimens that need to go the distance. A paper describing its use is available in the New Zealand Entomologist.


Palma RL. 1978. Slide-mounting of lice: a detailed description of the Canada balsam technique. New Zealand Entomologist 6(4):432-436

Walker AK, Crosby TK. 1988. The preparation and curation of insects. DSIR Information Series 163. DSIR; Wellington.


Samuel Brown said...

Another good description of the Canada Balsam technique is given by the NHM's Chalcidoid database. It is contrasted with Hoyer's medium, the procedure of which is described also.

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