|Gastropod shells and bodies extracted after microwaving|
And today for something completely different. Let's start with a description of the problem:
Extracting DNA from gastropods presents particular difficulties due to the capacity of the living animal to retract into the shell, resulting in poor penetration of the ethanol into the tissues. Because the shell is essential to establish the link between sequences and traditional taxonomic identity, cracking the shell to facilitate fixation is not ideal.
This sounds very familiar to me. While working on my masters project I had to remove tissue from coiled shells of a number terrestrial gastropods and some of those specimens were quite small and delicate. Most of the time I was working with a dissecting probe which tip I had bent to be able to reach the fully retracted animal. A very tedious and not always successful method to retrieve a tiny tissue sample for DNA analysis. Over the years a variety of methods to retrieve tissue without damaging the shell have been developed but for the most part they are suffering from the same problem. Due to the fact that they all take a fair bit of time they are not useful for large scale surveys or expeditions.
In a new paper a group of French researchers present an alternative method for the easy, efficient and nondestructive tissue removal from shells. It involves the use of a regular microwave oven. The use of microwaves in molecular biology is actually not unknown and has been applied in the extraction of DNA from viruses, bacteria, soil micro-organisms, and animal tissue. The colleagues placed the living gastropods in a microwave oven in which the electromagnetic radiation very quickly heats both the animal and the water trapped inside the shell, which results in the separation of the muscles that anchor the animal to the shell. If done properly, the body can be removed intact from the shell and the shell voucher is undamaged as well. The authors conducted comparative tests to find out if microwaving the snail tissue will have any effect on DNA extraction or subsequent PCRs. They couldn't find any difference in DNA quantity or quality.
The method was then implemented on a large scale during expeditions, resulting in higher percentage of DNA extraction success. The microwaves are also effective for quickly and easily removing other molluscs from their shells, that is, bivalves and scaphopods. Workflows implementing the microwave technique show a three- to fivefold increase in productivity compared with other methods.
That seems to be worth the effort. I wish we had thought of that 12 years ago.