Do you ever look at an insect part and think, “Wow, I wonder what 1.5 micrometer thick slices of it would look like in series from one end to the other, stained to maximize contrast between different tissues?”. No? Well you should. You really should.
Sectioning is a fairly time consuming process, but none of the individual steps are particularly complicated. They are as follows:
- Go catch something. Make sure it’s awesome. Then kill it (with Karnovsky’s fixative). Examples of awesome things: gasteruptiid metatibiae, evaniid metatibiae, aulacid metatibiae, pelecinid metatibiae, and trigonalid metatibiae. There are probably other things. Actually, everything.
- After ~48 hours in the fixative, rinse it off with sodium cacodylate buffer. Then rinse that off with water.
- The alcohol series: the water needs to be removed from the specimen slowly in increasing concentrations of ethanol. Remove the structure you will section (how about… the metatibia of a trigonalid? This trigonalid.). Then move the sample to acetone.
- Embedding: leave the specimen in a 1:1 mixture of acetone and eponate resin overnight. Then just eponate. Then put the sample in a special mold with fresh eponate, and put it in an oven so it hardens. When you take it out, it will look like this:
- Make a glass knife. Glue a little boat to it that can hold water.
- Shape the block. The cutting surface needs to be as small as possible, or your knife won’t last long.
- Put your sample and glass knife in the microtome. Line everything up perfectly.
- Start making sections!
- Corral sections away from the blade with an eyelash tool (an eyelash glued to a stick) and scoop them up with a loop tool (a loop of wire glued to a stick). Deposit sections on a slide.
- Heat the slide so water evaporates, adhering sections to the glass.
- Stain them. Toluidine blue and safranin works nicely.
- The end product:
- Now look at all of your pretty sections!
Taking into account the annoying human behaviors of eating and sleeping, the whole process takes me about a week from specimen acquisition to section viewing. Time consuming, but well worth it.