One step at a time
Thinking about doing molecular work for my research is incredibly daunting. The more I learn in classes and seminars about how to collect and analyze DNA the more terrified I become that it will totally consume my life, and that won’t be able to handle it. But I am learning to slow down my wild imagination and take things one step at a time.
Step one – collect some specimens for DNA!
Even this is not as easy as it sounds. I know how to catch moths and pin them… but what are the best ways to preserve them and preserve their DNA? DNA will start to break down if left out in the open. Extracting DNA from dried, pinned museum specimens has spotty success depending on how old they are. It is best if specimens are kept in ethanol (95% or 100%) and in a freezer (-20C to -80C preferable). Unfortunately, moths aren’t kept that way. They are pinned, spread, and left to try in glass-topped drawers.
How they are killed also can determine the DNA yield – cyanide is the preferred killing chemical, as opposed to ethyl acetate. That is not something typically written on labels, so if you are working with someone elses specimens, you have to hope you get lucky. Ethyl acetate is much more common as it is safer and cheaper.
An easy solution would be to take a whole moth and throw it into a vial of ethanol, and keep it in a freezer. However I still want to use my moths for morphological analysis (looking at wing patterns and body structures) so that wouldn’t work well for me. You can imagine that ethanol is not kind to delicate moth scales.
My solution is to remove three legs from the right side (just to be consistent) of my moths. That means carefully sterilizing my equipment between each use to ensure there is no contamination by stray scales or other body parts as I transfer the legs to their vials of alcohol. I am using little temporary tubes for now, and will move them to glass vials with proper labels soon. Luckily, legs are not as important for the analysis of moth specimens, so I am hoping some collections will let me take samples from their museum specimens to supplement my research.
Here you can see my first set of leg specimens, alongside the pinned moths. These are all individuals I raised from eggs last summer.
And what about the caterpillars I have kept in ethanol? Those could be useful too, however in many cases it is more difficult to accurately assign an ID to a caterpillar, and it is more difficult to remove a tissue sample for DNA without destroying the specimen. I will probably use some of them, especially in cases of cryptic species complexes.
Now I am anxiously waiting to see which moth will emerge from its pupa next… I still have a few dozen left.