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Collecting, Preserving, Identifying, and Recording Tardigrades
By Kenneth Nickell

Collection: The preservation and study of microinvertebrates, specifically specimens of the phylum Tardigrada, has been stifled by the lack of an adequate and attainable microscope slide mounting medium. In the past, Hoyer's medium has been used to fix specimens and make slides. However, it is difficult to obtain some of the ingredients in this solution e.g. chloral hydrate. It is especially difficult for individuals and high schools to purchase these chemical compounds. In order to get high school students involved in studying these microinvertebrates, a safer and easier method was needed.
  1. Members of the Phylum Tardigrada may be found among several different kinds of habitat. Mosses, leaf litter, and lichens are the most common places to investigate. Simply collect these kinds of material, dry them and then store in paper bags until it is convenient to begin dissecting the samples.

  2. Searching for specimens among lichens and other substrates is accomplished by soaking the material in distilled water contained in glass containers approximately 2 inches in depth by 4 inches in diameter (pic 1).

  3. After allowing samples to soak for 8 to 24 hours the glass containers can be examined with an observation scope (pic 2). It may be necessary to remove larger substrate pieces so the bottom of the container can be observed unobstructed.

  4. Most of the specimens will settle to the bottom of the jar and can be removed with a small eye dropper while viewing through the 30 or 40 power observation scope (pic 3).

  5. Tardigrades often attach themselves to micro flora and become difficult to persuade from the bottom of the jar. If that happens, carefully dislodge the critter with an Irwin loop or small sharp dissecting tool.

[Previously published method using micro-pipette or Irwin Loop]
Pic 1: Lichen in glass container
Pic 2: Observation Scope
Pic 3: Eyedropper extraction

Preservation (Optional):
The first step in preserving microinvertebrates is asphyxiating the organism without shrinking, distorting, or otherwise altering the overall morphology. After pulling the specimen and a tiny quantity of distilled water into the dropper place the contents of the dropper into a glass container of FAA solution. The organisms should immediately die, relax, and extend body parts well. FAA solution is a mixture of formalin, isopropyl alcohol, glacial acetic acid, and water. It can be purchased from Wards Natural Science, Rochester, NY. Leave the specimen in the solution overnight. Specimens can be left in the solution for longer periods of time without damage. Glass containers that can be placed under an observation scope are essential in order to find the specimen so it can be moved from subsequent solution to solution. To reduce evaporation, small glass plates can be used to cover the containers. Observations can be made through the glass covers and the covers also reduce exposure to the unpleasant vapors....

     + View the entire Preservation Methodology

Identification and Reporting:
Pic 4: Sample view of tardigrade from observation scope. Tardigrade present. After tradigrades have been extracted from the substrate, use a 40 power (or better) microscrope to make visual identifications. The following resources will help to better identify genera and species.

  1. Use the PathFinder Science key to identify the genus of the animal.
  2. A few texts are available for assisting with species identification, including:
  1. Record the substrate type (tree lichen, moss, etc.) you are collecting your tardigrades from, such as tree lichen, rock lichen, moss, water, etc.
  2. Collect the latitude and longitude for each sample and record in the table below [Available Options for lat/long].
  3. Record the Tardigrade Genus and species if available.
  4. The students schould upload the recorded data through the Data Submission Area. This could include one or more digital photos of the tardigrade.

    The table below may be helpful for recording data prior to submitting it at PathFinder Science.
    School Name and Number
    Sample Date
    Identifying Sample number
    Substrate sample collected from
    Tardigrade Genus
    Tradigrade Species if possible

Additional help:
A Quicktime video introducing tardigrades and basic sampling techniques is available. The technique better reflects the first sampling protocal used at KanCRN/PathFinder Science (1997-2002). This is a large file so anticipate a long download time.

  1999, KanCRN Collaborative Research Network