PHYLUM: PROTOZOA Methods of Locomotion: 1. Amoeboid movement By: AAKRITI
METHODS OF LOCOMOTION IN PROTOZOANS: Basically there are four known methods by whichthe protozoans move 1. Amoeboid movement 2. Swimming movement 3. Gliding movement 4. Metabolic movement
AMOEBOID MOVEMENT: This type of locomotion is also called as pseudopodial locomotion. Here locomotion is brought about by the pseudopodia. It is the characteristic of rhizopod protozoans like Amoeba proteus and Entamoeba histolytica. Also such movement is exhibited by amoeboid cells, macrophages and phagocytic leucocytes like monocytes and neutrophils of metazoans. Various theories have been proposed to explain the amoeboid locomotion.
Sol Gel theory: It convincingly explains the mechanism involved in the formation of pseudopodia. . This theory, also known as Change in viscosity theory was advocated by Hyman. Later Pantin and Mast explained this theory. According to this theory, the cytoplasm of amoeba can be distinguished into outer ectoplasm/Plasmagel and the inner endoplasm/Plasmosol. The plasmagel which forms the outer layer of the cytoplasm is thick, less in quantity, non-granular, transparent and contractile.
. The plasmosol which forms the inner layer of the cytoplasm is more in quantity, less viscous, fluid like, more granular and opaque Due to change in the viscosity, the plasmagel and plasmosol inter-convert and consequently the pseudopodia form and disappear causing the movement of Amoeba . This inter-convertibility of plasmagel and plasmosol is physico-chemical change . Gel becomes sol by taking water and sol becomes gel by losing water
Uroid acuole Nucleus Plasmasol Hyaline cap Plasmagel Zone of solation Zone of gelation SOL GEL THEORY-AMOEBOID LOCOMOTION
Amoeboid locomotion can be explained in the following steps: Step 1: Initially Amoeba attaches itself to the solid substratum by the plasma lemma at the temporary anterior end. Step 2: Then the hyaline layer of the ectoplasm at the anterior end forms a thickened hyaline cap. It is the first stage in the formation of the pseudopodium Step 3: Behind the hyaline cap, a point of weakness in the elasticity of plasmagel is formed. Hence the inner plasmosol flows forward, forming a pseudopodium.
Step 4: The plasmosol that flows outward behind the hyaline cap changes its colloidal state from sol to gel and joins the ectoplasm Step 5: The outer region of the plasmosol, which is flowing forward undergoes gelation and produces a rigid plasmagel tube. The gelation of plasmosol extends the plasmagel tube forward Step 6: Two ends appear in Amoeba at this stage The anterior end is smooth with the rounded surface which the retractile end also called as Uroid has a wrinkled surface
Step 7: Around the region of the hyaline cap, an annular region of sol to gel transformation is formed. It is called the zone of gelation. At the uroid end a region where gel transforms into sol is called as zone of solation Step 8: Plasmagel at the uroid end changes into sol and flows forward continuously through the gelatinized tube. As the plasmosol flows forward the pseudopodium elongates further and the body of amoeba moves in that direction. The ectoplasm does not move but grows at the leading tip and is broken down at the uroid end
Step 9: The gelation at the advancing end and the solation at the trailing end occur simultaneously and at the same rate thus making the forward movement of amoeba continuous Step 10: The contraction of the plasmagel at the trailing end causes hydraulic pressure on the sol and makes the plasmosol flow forward continuously in the plasmagel tube. Step 11: As the pseudopodium advances continuously in the direction of the movement the body of amoeba also moves
Graduate in Biology Pursuing M.Sc. in Zoology Power is gained by sharing knowledge not hoarding it.