Ethanol and propylene glycol are both used to preserve mites, and each have their drawbacks (i.e., evaporation and specimen distortion). Some people add a small amount of glycerol to vials of ethanol to prevent samples from drying out over time if containers prove less than perfectly airtight. Does anyone have experience with the long-term performance of ethanol/propylene glycol mixtures as preservatives for mites, and particularly for oribatids?
Hello dear colleague,
I recommend you to read my published paper in 2016 explaining in detail a good experimental preservation method for mites and Collembola in long-term.
Good luck, Elaheh
Dear Kara Skye Gibson
You are right that different methods of keeping mites are being used now. However, we still use 70% ethanol. It allows you to preserve the material for decades. However, so that it does not evaporate, it is better to use plastic tubes with tight-fitting lids. If then it is necessary to restore the mobility of the extremities, etc. We steam them in a water bath.
Regards, Pushkin Sergey Viktorovich
Thank you for your kind advice, Elaheh Daghighi Masouleh and Pushkin Sergey Viktorovich. To clarify, I am interested in preserving microarthropods in this way both to prevent sample degradation due to potential ethanol evaporation (and thus reduction of ethanol strength), and because examining samples containing hundreds of animals is easier in a more viscous fluid (in ethanol, they sometimes drift around in the dish as evaporation occurs, making it difficult to count them).
Given the advantages of using an ethanol/propylene glycol solution for my purposes, can anyone think of a reason this might be a bad idea, provided the ethanol concentration stays above 70%? I am imagining that the propylene glycol might settle in the bottoms of the vials over time (where the microarthropods are), but since propylene glycol is itself a preservative, hopefully this would not be a problem?
Dear Kara,
The usual concentration for ethanol is 70%. The more percentage makes specimens fragile in long-term even in short-term. About propylene glycol, I should say it may not go to the bottom of vials and it helps to reduce the evaporation of ethanol.
Best, Elaheh
We used 70% ethanol for the morphology analysis. It allows the animal to keep its normal body. While 90% ethanol was used to perform the molecular analysis, it is too concentrated and shrinks the organs of the animal. I have not used propylene glycol yet.
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