Collecting Amoebae

I get my material from all kinds of water, especially from freshwater marshes and ditches in the central area of the Netherlands. This region has very different types of water, from oligotrophic to eutrophic, peat swamps to lakes, streams to standing water. I always carry some small tubes in my pocket, in case I have an opportunity to sample something. I usually collect amoebae from the sediment of ponds and ditches.

My favorite deeper water tool to collect amoebae is a jar tied on a long thin rope or an extendable pole. I toss the jar into the water, wait for it to reach the bottom, then pull a little to move the jar and let some sediment swirl into the jar. Then I pull the jar out of the water and transfer the sample to a clean glass. I label the glass with the sample location name and date. I also take a photo of each sample on location. My camera embeds the GPS coordinates and time in the photo.

I use the jar-on-a-string method because the bottom of most ponds and lakes here is covered with a thick layer of decomposing organic matter. That’s why I usually don’t have any problems with sand grains in my samples, which can be very annoying in a wet mount. Sand can cause several problems with slides. When I collect material from water with a sandy bottom, usually covered with a thin layer of decomposing organic material, I try not to absorb the sand and, when possible, I use a large pipet.

At home, I scan the samples within 24 hours to see if they’re worth studying further. Promising samples are stored at room temperature, avoiding direct sunlight. I usually leave about two inches of water above the sediment. Depending on the nutrients and the associated microbial sequence, samples can stand for two days or months.

In the spring, pieces of soil material float due to algal activity. This material can be very rich in all kinds of amoebae, for example, large Chaos amoebae. I collect this material with a pot on a long stick.

Aquatic plants and wet mosses are squeezed by hand, causing the water to flow into a glass. These samples are then filtered to remove larger particles such as moss leaves. Dry mosses are collected in a plastic bag. At home, I put them in a large bowl and add rainwater. I stir and squeeze the moss, remove the plants, let the mixture settle, and collect the residue in a smaller glass.

I use an inverted Nikon Diaphot microscope to find and isolate large testate amoebae with shells that can easily break under a coverslip in a normal wet mount. After isolating the shell, I cover it with a slip, supported by pieces of a broken coverslip. I also use the inverted microscope to isolate amoebae for staining, mounting, and culturing.