Pelomyxa palustris (Binucleate form)

This species of amoeba is usually found in early spring at the bottom of the pond where it hides deep within the mud and detritus. It can also be seen in collected water after a few days when it settles down and migrates to the surface of the mud. This sample was taken from Speakmans pond in Epping Forest and it was just by accident that I happened to spot this very large amoeba. I had noticed many small round objects but did not think that they were amoebae and only after a while did they start to exhibit any sign of life. It moves very slowly through the water and spans out to about 350um but can apparently reach a span of anything up to 5000um. It engulfs anything that gets in its path from algae, sand particles and anything else that it can take on board. It also has at least two species of endosymbiotic strains of bacteria that can be found living within the cell body. Pelomyxa moves by an eruptive wave at the anterior end with the cytoplasm flowing into this monopsuedopodium. It reproduces by plasmotomy with the main cell body splitting up in to three or four smaller bodies. There were supposed to have been many different species of this organism but now many doubt that this is the case. In figure (a ) many small pseudopodia seem to start to erupt but always remain small in nature and never grow into major pseudopodia. Figure C shows a binucleate form of Pelomyxa. The photographs were taken with on a Leitz Orthoplan microscope using differential interference objectives and also the Leitz Orthomat camera. The film used was 160 tungsten.