ZooGene Sample Preservation Protocol

Unsorted zooplankton samples can be preserved in 95% ethyl alcohol for later molecular genetic analysis. Samples intended for use in the molecular characterization of a particular species (i.e., molecular systematics) should contain 10 - 20 adult individuals (ideally including both males and females) of the targeted species. Samples intended to allow examination of geographic variation within a species (i.e., population genetics) should include 30 - 50 individuals (ideally adult females) per sample.

In most cases, the sender should confirm the identification of the desired species. The selected individuals should be removed from the sample and place in a small glass vial (5 - 20 ml) with a plastic top that prevents evaporation. Please include a label inside the vial, writing in pencil.

Please follow the sample preservation protocol below.

ALCOHOL PRESERVATION of samples for molecular analysis

  1. Samples collected with minimum damage to plankton are preferred (i.e., short tows, rapidly preserved). Suitable net mesh sizes can vary between 100 um to 333 um for copepods, 550 um for euphausiids. Samples need not be quantitative; non-quantitative aliquots or splits of samples are also fine.

    Because of the rapid rate of DNA destruction, zooplankton samples should be preserved IMMEDIATELY following collection, while the individuals appear lively, transparent, and healthy. Individuals that appear moribund or dead should not be preserved for molecular analysis.

  2. Drain samples of excess seawater (over nitex mesh of same size or smaller than the net used for collection).

  3. Place sample in round-sided, flat-bottomed glass jar (i.e., avoid jars with corners where putrefaction can occur and opaque jars where that sample cannot be easily observed). Add 95% ethyl alcohol; there must be 3 to 4 times more alcohol than plankton volume - especially for larger individuals, such as euphausiids. We recommend removing fish, gelatinous plankton, and other large non-essential organisms from the samples to be preserved in alcohol.

    NOTE: DENATURED ALCOHOL CANNOT BE USED FOR SAMPLE PRESERVATION FOR MOLECULAR ANALYSIS. 100% ETHYL ALCOHOL SHOULD ALSO NOT BE USED FOR PRESERVATION FOR MOLECULAR ANALYSIS: it frequently retains traces of the benzene, or other solvent, used to displace the remaining water from the alcohol.

  4. Place a label inside the jar or vial, writing in pencil. Unprinted labels are preferred since the ink may dissolve in the alcohol. Use small labels made from acid-free paper. (We have discovered that some labels change the sample pH significantly, especially in small volumes).

  5. After 24 hours, drain off the alcohol (using Nitex or mesh of the same size as the collection net or smaller) and replace with fresh alcohol. Check periodically for evaporation and putrefaction. Continue changing the alcohol daily until the liquid remains clear (pigment leaching is OK, but flocculent matter is not).


The samples can be mailed in small packages via airmail. The vials should be wrapped in parafilm or other material to prevent leakage. Placing vials in styrofoam molds for support is ideal; they should be well wrapped to prevent breakage. We usually label the contents as "scientific samples" and claim "no commercial value" for customs purposes. Samples may be sent collect or cash-on-delivery (COD) to Ann Bucklin at the University of New Hampshire.

Last modified: July 5, 2000