Скачать или смотреть Dissection of a cyclopoid copepod

Here's a photo album of the results: https://imgur.com/a/TeiiG1j

5th legs starts at 1:50, showing the result at 2:25 (it's the two structures hanging from the segment on the right).
For a closer look at a 5th leg dissection:    • Cyclopoid copepod 5th leg dissection  

This video shows a full dissection of a female cyclopoid copepod, starting with the 1st and 2nd anntennae (removing the ''scalp''), then cutting between the fifth and sixth thoracic segments
(somites of the fourth and fifth legs), cutting the 4th legs (other structures like the rest of the swimming legs could be cut at this step if required), and finally tearing the 5th leg somite with both 5th legs still attached.

This is done on a bino, at 80-100x (the scale shown on screen is probably incorrect).

I'm using a 15 gauge needle mounted on a handle for my left hand and a 25 gauge ''spearhead'' MVR knife for my right hand, also mounted on a handle. The knife can be replaced by sharpening one side of a pair of fine tweezers, or probably even by using a stiff needle and applying more pressure when laid flat. I switch to another 15 gauge needle for my right hand at the end just to remove the pair of 5th legs. I always use a thumb grip, with my thumbs resting on the surface for stability.

It's important to always position the animal on its dorsal side, especially for the final dissection of the 5th legs. With my right hand, I gently ''tap'' the junction between the 5th leg somite (the ''winged'' segment) and the (round) genital segment until I find a good point of entry for the needle. Make sure to aim between the pair of 5th legs to not damage them. Finding the sweet spot for entry is by far the hardest part. Too low and the genital segment will stay attached and you won't have a good view, too high and you will just rip the 5th leg somite apart and both legs will stay attached. More often the latter will happen, if it does, try to go again from under the segment (the dorsal portion) or just make a rough cut around the region with the knife.

Once I have a good point of entry, I apply pressure on my right hand and use my left hand to tear the urosome away from the 5th leg somite, leaving only the segment with both legs still attached and (hopefully) still intact and visible.

I also recommend to try to observe the 5th legs and take pictures before making the final tear, as it's very easy to damage them they are normally easy to observe with the swimming legs out of the way.

Forgot to film the final step which is to flip the 5th leg somite on the ventral side for better observation on a dissecting microscope.

One last trick: if you have to remove all 4 swimming legs, start with the 4th (just like in the video) and move it to one side of your slide. Then cut the 3rd legs in the same way, then move it to the other side of the slide. Then cut the 2nd, and move it to the same side as the 4th, then cut the 1st and place it to the same side of the 3rd, and then move on to the 5th leg dissection. This is because I find the 4th pair can be confused with the 3rd, and the 1st can sometimes be confused with the 2nd, but 1-3 and 2-4 are normally easy to tell apart.

Feel free to ask any questions about the procedure!