Shape, movement and nutrition Amoeba

the forms of pseudopodia, left: polypodial , lobose; monopodial , lobose; filose; conical; reticulose; tapering actinopods; non-tapering actinopods

amoebae move , feed using pseudopods, bulges of cytoplasm formed coordinated action of actin microfilaments pushing out plasma membrane surrounds cell. typically, amoeba moves extending pseudopod, attaching substrate , filling cytosol, releasing rear portion attachment substrate, results in organism being propelled forward.

the appearance , internal structure of pseudopods used distinguish groups of amoebae 1 another. amoebozoan species, such in genus amoeba, typically have bulbous (lobose) pseudopods, rounded @ ends , tubular in cross-section. cercozoan amoeboids, such euglypha , gromia, have slender, thread-like (filose) pseudopods. foraminifera emit fine, branching pseudopods merge 1 form net-like (reticulose) structures. groups, such radiolaria , heliozoa, have stiff, needle-like, radiating axopodia (actinopoda) supported within bundles of microtubules.

morphology of naked lobose amoeba

free-living amoebae may testate (enclosed within hard shell), or naked (a.k.a. gymnamoebae, lacking hard covering). shells of testate amoebae may composed of various substances, including calcium, silica, chitin, or agglutinations of found materials small grains of sand , frustules of diatoms.

shell of testate amoeba difflugia acuminata.

to regulate osmotic pressure, freshwater amoebae have contractile vacuole expels excess water cell. organelle necessary because freshwater has lower concentration of solutes (such salt) amoeba s own internal fluids (cytosol). because surrounding water hypotonic respect contents of cell, water transferred across amoeba s cell membrane osmosis. without contractile vacuole, cell fill excess water and, eventually, burst.

marine amoebae not possess contractile vacuole because concentration of solutes within cell in balance tonicity of surrounding water.

amoeba phagocytosis of bacteria

the food sources of amoebae vary. amoebae predatory , live consuming bacteria , other protists. detritivores , eat dead organic material.

amoebae typically ingest food phagocytosis, extending pseudopods encircle , engulf live prey or particles of scavenged material. amoeboid cells not have mouth or cytostome, , there no fixed place on cell @ phagocytosis occurs.

some amoebae feed pinocytosis, imbibing dissolved nutrients through vesicles formed within cell membrane .