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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 4742

Andrzej Grebecki; Locomotion of Saccamoeba limax. Arch.Protistenk 134:347-365, 1987

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The unidirectional locomotion of Saccamoeba limax is composed of a succession of pseudopodial cycles. Each new pseudopodium arises on the tip of its predecessor, as a new front with a hyaline cap. After the period of expansion, the old frontal edge is retracted backwards simultaneously with the initiation and expansion of a new front from one discrete site on the surface of the old one. This cycle is accompanied by establishing a new attachment to the substratum and its later detachment. Apparently monopodial Saccamoebae become typically polypodial when the attachment is lacking or restricted to the rear body end. All the ectoplasmic material is steadily retracted toward the attachment sites which were stable at the moment of observation. It produces the fountain movement in front to attachment zone and tail retraction behind it. The fountain is very well expressed by the movements of cytoplasmic inclusions and of the outer cell contour. The tail retraction is never interrupted and much more steady than the progression of the front. Oscillations of the frontal velocity exceed in amplitude and precede in time the same oscillations in the withdrawing tail. The fronts respond negatively to the contracting stimulation by light and positively to the relaxing influence of shade. It is highly probable that the generalized cortical contraction theory of amoeboid movement applies to S. limax. According to this concept the contractility of the whole cell periphery generates a steady motive power, while a relative relaxation in the front controls the rate and direction of the endoplasmic flow and cell locomotion.