Extraction equipment
- two beakers (preferably with screw cap lids, which allows better mixing)
- a table spoon
- a funnel
- filtered seawater (preferably from the sample location)
- MgCl2 solution (as an anesthetic, at 71g/l for normal strength sea water)
- always close your MgCl2 container properly. It is highly hygroscopic.
- large and small petri dishes
- nets (63 or 100µm mesh size)
- small pieces of paper labeled with pencil to identify the sample (placed directly into the Petri dish)
- dissecting microscopes to observe the samples
- sample analysis datasheet
General procedure
Place two table spoons of sand into a beaker, add about double the amount of water and add a similar amount of MgCl2 solution. Gently shake the beaker to mix the solution well with the sand, and leave for about 5 minutes. Stir up the sand again, washing the animals into the supernatant, and decant the liquid through a net and pour the water back onto the sand sample. The optimal net size depends in the species and sediment (small nets catch smaller worms, but also more sediment). Place the net into a Petri dish with seawater only, so that the worms can recover from the anesthetic, and check for worms under the dissecting microscope, both on top and below the net, and move them into small Petri dishes. You can repeat the washing of the same sand sample a couple of times, but don't leave it for too long, as the anesthetic will eventually damage the worms (for some papers on different extraction methods see the bottom of this page).
Bottle extraction
For vegetation samples and samples with a high sediment content, place the sample into a transparent and open beaker (we often use cut-off PET mineral water bottles), and let it stand for some days. As the oxygen gets depleted in the bottom of the sample, the worms will start to crawl up along the wall of the beaker, where they can be collected with a pasteur pipette. A strong light source and a black background help a lot (and being a bit short-sighted also helps). Eventually the samples will go bad, but one can harvest worms like this for several days. Also, it may be useful to have a rotating table to access all sides of the beaker without shaking it too much, but this is not so important. If the vegetation tends to float, you can add some stones or a metal grid to push it down.
