Locomotor organelles found in Protozoa:
| Pseudopodia | Temporary structures formed by streaming flow of cytoplasm (false feet) Lobopodia Lobe like Pseudopodia with broad and rounded ends composed of both ectoplasm and endoplasm Move by pressure flow mechanism e.g. Amoeba Filopodia Filamentous pseudopodia tapering from base to pointed tip composed of Ectoplasm only May branch and form simple networks e.g. Euglypha Reticulopodia Filamentous (rhizopodia or myxopodia) Filaments are branched and interconnected extensively 2 way flow of cytoplasm e.g. Foraminiferans Axopodia Almost straight, radiating from surface of the body Each axopodia contains a central axial rod, covered by granular and adhesive cytoplasm. 2 way flow of cytoplasm e.g. Heliozoans |
| Flagella | Locomotion organelles of flagellate Protozoa: Euglena, Trypanosoma Thread like projections on the cell surface Contains an elongated stiff axial filament, enclosed by an outer sheath Axoneme: 9 longitudinal paired fibres, surrounding 2 central longitudinal fibres Each of the Peripheral fibres bears a double row of short arms Axoneme arises from a basal granule. |
| Cilia | Resemble Flagella in their basic structure Highly vibrate small ectoplasmic processes 9 + 2 paired longitudinal fibres arrangement, 1 fibril in the peripheral pairs bears short arms Central fibres are enclosed within a delicate sheath Each cilium arises from a basal body Spoke like radial lamellae between central and outer fibrils |
| Contractile structures | Contractile structures in Pellicle or Myoplasm are called Myonemes. Euglena: Ridges and grooves Larger ciliates: contractile myofibrils Trypanosoma: Microtubules |
Methods of Locomotion:
| Amoeboid | Formation of Pseudopodia by streaming flow of cytoplasm Locomotion by Pseudopodia is possible only over a surface Sol Gel Theory (Mast and Pantin, 1925) of Amoeboid movement and formation of Pseudopodia: Contraction of ectoplasmic tube (plasma gel) at the posterior part of the body causes the endoplasm (plasma sol) to flow into the expanding pseudopodium. Involves continuous solation at the posterior end, and gelation at the anterior end. |
| Flagellar | Flagella need liquid medium for locomotion Some or all axonemal fibres are involved in movement Adjacent doublets slide past each other, causing the entire flagellum or cilium to bend Cross bridges are formed and energy utilised for the process is supplied by ATP Paddle Stroke: Sideways lash with the flagellum held out rigidly Relaxed recovery stroke in which flagellum, strongly curved is brought forward Animal moves forward, gyrates and rotates on its longitudinal axis Undulating Motion: Wave like undulations Tip to base: move forward Base to tip: move backward Spiral undulations facilitate rotation Conical Gyration: Spiral turning of flagellum like a screw exerts propelling action, pulling the animal forward through water with a spiral rotation |
| Ciliary | Most ciliates appear to move in a spiral path, rotating on their axis as they go. Basal bodies of all cilia are inter-linked by kinetodesmata, ensuring coordination Large ciliates are the swiftest Most likely based on contraction of peripheral fibres Movement mostly occurs during the backward effective stroke rather than the forward recovery stroke. |
| Metabolic | Typical of certain flagellates and most sporozoans at certain stages of their life cycles Gliding, wriggling or peristaltic movement Contractile myonemes present in pellicular walls are responsible or this kind of movement. |