Pelomyxa (peal-o-mix-a), a large pelobiont which developed some reputation as possibly the most primitive eukaryote. This argument was based on the fact that it does not have mitochondria, conventional dictyosomes if any, flagella are aberrant, and nuclear division was also thought to be aberrant. The arguments for a primitive status now seem to be unsound. Cytoplasm with small particles of sand. eats algae and detritus. Moves with fountain-flow motion (cytoplasm moving forward up the centre of the cell and then spilling out near the front. Posterior end crumpled, to form a uroid. Phase contrast micrograph. This picture was taken by David Patterson and Mark Farmer of material from freshwater sites in the vicinity of the University of Georgia in Athens, Georgia, USA) in April, 2001 and from collections of organisms maintained at the University. Image copyright: D. J. Patterson and Mark Farmer, image used under license to MBL (micro*scope).
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From the collection
Athens, Georgia, USA
|Description of Pelomyxa palustris: Pelomyxa palustris is usually reported as a large multinucleate amoeboid pelobiont, 100-5000 microns long, with small non-motile flagella, endosymbiotic bacteria, refringent cytoplasmic granules (sand and food particles); movement takes place usually as a monopodial progression, with a central forward flow of cytoplasm along a single axis, and the cytoplasm spills outwards at the anterior-most tip of the flagellum. The posterior uroid is involved in the capture of food which is comprised of detritus and algae. The cysts are about 100 microns in diameter. This species has been reported from freshwater and soils. This species has many inactive flagella attached to single basal bodies. Cones of microtubules arise from the bases and sides of the basal bodies; sometimes enclosing a nucleus. The nuclei may also be surrounded by endosymbiotic bacteria instead of microtubules. The axonemes of the flagella may or may not have the standard 9+2 arrangement of microtubules. |