Monday, August 11, 2008

Coddington mount modified

The original Coddington (1983) mount is to be found here. I have learned about the modified mount from Fernando Alvarez-Padilla, and wishes take no credit for it. I simply try to summarize the whole procedure in a way it is accessible for more people.

I have used the modified Coddington mount (henceforth MCM) to make the two images, where the sperm ducts are also visible.

Practical information about the required elements (all of these are easily accessible in many shops; however I’ll provide “a source” as well, which comes from a quick google search on the item, unless stated otherwise):


#1 Microscope slide (a source)


#2 Cover slips (a source)


#3 Vaseline (a source)


#4 Glass scribe (I bought one in a hardver store, which was cheap, and hard to use. I finally ended up in using a Bel-art glass scibe, which turned to be excellent)


#5 Scale cover glass 22mm x 60 mm (a source). Slide covers are cheap, and at the same time very hard (if not impossible) to clean. It is possible to clean the area above the specimen with a dry paintbrush, but after a while and if any liquid has been on the other surface of the cover, it is much better to trash the cover glass, then try to clean it.


#6 Methyl Salicylate also known as methyl-benzoate (see details on the label above). You can alternatively use lactic acid, Hoyer solution, clove oil, etc. for the same effect. I have experience mainly with methyl salicylate)

Note: methyl salicylate is an apolar aromatic liquid. This means with water it creates a milky liquid, with some gas generated aside. This might be sometimes useful (tracing ducts in a vulva), but since it is gas, it will show as black spot on an image. You can leave the specimens in methyl salicylate, but be aware it sometimes weaken the joints. To avoid this, use 96% alcohol bath to rinse the specimen before applying methyl salicylate (same apply after photographing the specimen). To wash down methyl salicylate use common household detergent, and only after that apply water. Rinsing the microscope slide with alcohol after this, will give you spotless drying. It is important to avoid dusting the cover glass and microscope slide. Methyl salicylate melts plastic, so use glass equipment only. Exceptions are the plastic micropipettes which could be used, but then needed to washed by either cc alcohol or a detergent.

#7 96% Alcohol

#8 Detergent

#9 Tooth pickers

#10 Glass dishes

#11 Ruler

#12 Compressed air duster (a source)

#13 Micropipettes


Make a Coddington mount step by step

Step1: Glue few (depend on the size of the palp, or other structure you want to examine, the smaller it is the fewer slips you need) cover slips on a microscope slide. I normally use nail polish.

Step2: Use your glass scribe to cut the scale cover glasses into narrow and long pieces. Use a ruler to aid your cut! Dust off the glass pieces, and store these glasses in a box where they cannot dust.

Note: you could skip this step. A full cover glass is also good, but a bit harder to manipulate afterwards. See an example below.


Step3: Apply Vaseline on the top coverslips and gently put the cover glass on top.

Step4: put methyl salicylate on the microscope slide, within the reach of the cover glass. Use enough, but not too much. Quantity depends on the height of the cover glasses.


With the Coddington mount (CM) you should be able to move and position your specimen. However for smaller items you have to use fewer covelslips and this still won’t guarantee your specimen remains in position.


The Coddington mount should look like this (green is Vaseline, yellow is Methyl-salicylate).
Modify the Coddington mount: If you apply enough Vaseline, and do not press hard the cover glass into it, the other end of the cover glass could be pressed down creating a triangle. This would create a bigger surface tension fixing conveniently your specimen. Use tooth pickers to manipulate the cover glass, and never touch it from above.

With bended pins, or careful movements of the cover glass you can position and reposition it quite easily. Single hair brushes on tooth pickers are among the best tools to achieve this. Due the variable height you can use a bigger variety of items and even at the very same time. You also could position specimen in many angle in a higher space and fixing them by moving them towards the end of the glass cover.


The difference between the CM and MCM. CM above, MCM below.


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