26 b. Phylum Gymnamoeba: Gymnamoebas are amoeboid protists that move by forming and extending a pseudopodium , at any point on their body surfaces. The body, including cytoplasm and nucleus, then oozes into the pseudopodium. Make a vaseline mount slide of Amoeba proteus and view it under the lowest power on your compound microscope. Amoebas are bottom dwellers so take your sample from the bottom of the culture dish. Note the following cellular structures: plasma membrane ; leading pseudopodium (plural, pseudopodia), nucleus (slightly brownish, more finely granular than the cytoplasm, and disk-shaped); contractile vacuole ( s ) (intermittent in occurrence, variable in position, but always round and clear and used to rid the amoeba of water gained osmotically); and food vacuole ( s ) (if present). The cytoplasm in these protists is differentiated into two regions: the ectoplasm is nonflowing and more peripheral in position, while the endoplasm is more fluid and more central in position. Examine the tip of an advancing pseudopodium for sudden bulges of ectoplasm.
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Cytosol, Amoeboid, new pseudopodia attach