There is immense variety in their movements but basically all the movements in animals are of only three types. These basic types are the - amoeboid movement, ciliary movement and muscular movement.
Amoeboid movement is the “ amoeba-like movement”. It is the most basic of all type of movements and perhaps the least well understood - though some amoebae have been studied now for 200 years. The Amoeboid movement is seen in amoeba ( e.g. Amoeba proteus) and several other forms of life, like - cellular slime molds (e.g. Dictyostelium discoideum ), and even in some cells in man.
It is the crawling movement of cells – seen in human body in Kupffer cells of liver, various kinds of white blood cells like- monocytes and neutrophils, cancerous cells showing metastasis, macrophages (the cells which eat ‘ foreign bodies’) in connective tissue. It is seen in animal cells - in tissue culture and in cells of developing embryos.
It is the movement done by changing shape of an entire cell and the cell must not have a rigid cell wall. Amoeboid movement shows that individual cells can sense changes in the environment and respond to them by going towards or away from such stimuli.
Amoebae change shape by forming pseudopodia (false feet). They are false feet as they are produced at any point on body and have no fixed position. Their numbers are not fixed and they vary from zero to several dozens. Also, a given pseudopodium can be extended or contracted. Our legs / hands are at a fixed position and are always 4 in numbers ( in all normal humans). We just can’t elongate a hand or flow into it nor can shrink it till it disappears.
While several theories have been trying to explain the amoeboid movement for last several decades there is overall agreement in following points –
Amoeboid locomotion begins with protrusion of a pseudopodium from one end of a cell.
There is continuous new cell membrane formation at leading edge of the pseudopodium. There is continuous exocytosis at middle and rear portion of the cell.
The pseudopodium is attached in its leading position on a base and rest of the cell body is pulled towards the growing pseudopodium.
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