Sample Preservation
Please follow these recommendations to ensure your samples arrive at our lab in good condition.
Using Alcohol
Alcohol is a preservative, not a fixative. It does not penetrate invertebrate tissue as well as fixatives such as formalin. Therefore, unless alcohol is used in sufficient strength and quantity, the sample will decay.
We do not use formalin because it is a carcinogen and a mutagen. Please do not use dyes such as Rose Bengal. They do not facilitate sorting of freshwater samples, and some dyes are suspected carcinogens.
Denatured Ethanol: We recommend using 90-95% denatured ethanol to preserve field samples. Select a technical rather than reagent grade of ethanol to save on cost. Unless you have a special Alcohol, Tobacco, and Firearms permit, you can only purchase denatured ethanol. “Denatured” means other alcohols and smelly ketones are blended with the ethanol to keep it from being consumed.
Isopropyl alcohol: Also known as rubbing alcohol, isopropyl alcohol can be used in a pinch. It is available at grocery, drug, and discount stores. If you decide to use isopropyl alcohol, purchase 90% rather than 70% concentration.
How to Preserve Your Samples
1
Never leave unpreserved samples exposed to direct sunlight because the invertebrates will die and decay rapidly.
2
Preserve samples within an hour of collection.
3
Preserved samples do not have to be refrigerated, but they should be stored in a cool place away from direct sunlight.
4
Be as gentle as possible when handling samples so that invertebrates are preserved intact rather than ground into pieces.
Filling the sample bottle
Sample bottles should be filled at most half full with a sample of sediment, bugs, and debris (see photo). Ensure the sample is well drained of water before transferring it to the bottle. Then, fill the bottle with 90-95% denatured ethanol or isopropyl alcohol. Invert the bottle several times to ensure the alcohol is well mixed with the sample.
For samples that contain much fine detritus or filamentous algae, which retain a lot of water, we recommend that half the alcohol be decanted off at the end of the day and replaced with fresh alcohol.
