Locomotion in protozoa

• Protozoa move either by gliding or by means of organelles like pseudopodia , cilia or flagella.
• Gliding movement is seen in toxoplasma, sarcocytis.

a. Pseudopodia:

• Temporary organelles formed and retracted as per need.
• Cytoplasm continually flows forward/ outwards and forms process of various shapes called pseudopodia (false feet).
• Organism moves along by the flow of its cytoplasm into pseudopodia. Solid food particles are taken in by encircling with pseudopodia. Example: Entamoeba.

b. Flagella:

• Contracting fiber, arising from a structure called basal body.
• In some species, it is attached to body of protozoan along its length. When flagellum beats, cell membrane is pulled up to form an undulating membrane.
• Sometimes, it projects beyond the protozoan body as a free flagellum.
• Slender, whip-like structure, composed of central axial rod known as axoneme, surrounded by cytoplasmic sheath. Axoneme arises from structure known as kinetoplast which consist of nucleus or chromatin mass known as kinetonucleus or parabasal body.
• Near kinetoplast, another granular substance is present known as biepheroplast or basal granule.
• Axoneme consist of nine peripheral and one central pair of microtubules ( 9+2 arrangement).
• Flagellar movements are generally helical waves that begin at base or tip, pushing fluids along flagellar axis. Resulting body movement may be fast or slow, forwards, backward, lateral or spiral, depending on length of flagella, size of and distance between waves it generates.

c. Cilia

• Fine protoplasm eye-lash like organelles originating from basal granule embedded in pellicle or ectoplasm.
• Each cilium is composed of central elastic axial filament covered with contractile sheath.
• They may be of equal length or their length may vary. They are arranged in definite patterns on body surface, which are further used for classification of cilia.
• Beside locomotion, they also aid in ingestion of food particles.
• They bend rhythmically together and propel the organism through medium in which they live.