Pseudopodia

Pseudopodia, from Greek pseudo meaning false and pod meaning foot, are temporary cytoplasmic projections used by certain eukaryotic cells for locomotion and feeding. They are not fixed organelles but dynamic extensions of the cell membrane and cytoplasm that alter shape as the cell interacts with its environment.

Most commonly associated with amoeboid protists such as Amoeba species, pseudopodia enable amoeboid movement by cytoplasmic streaming: actin-rich cytoplasm flows toward the leading edge, extending a protrusion that anchors to the substrate and pulls the cell body forward. In many cells, pseudopodia cooperate with adhesion sites and contraction of the cell cortex to drive movement; in immune cells such as macrophages and neutrophils, pseudopodia enable navigation through tissues and engulfment of particles.

Forms of pseudopodia vary. Broad, rounded lobopodia push the cell over surfaces; slender filopodia are finger-like extensions; some protists produce net-like reticulopodia, or stiff axopodia supported by microtubules. The extension mechanism relies on actin polymerization at the protrusion tip, regulated by signaling pathways including Rho family GTPases, and is coupled to membrane trafficking and endocytosis.

Pseudopodia play a key role in phagocytosis: engulfing bacteria, algae, or other particles by surrounding them within a phagosome. They are also used to capture prey or debris in environments where cilia or flagella are absent. In certain parasitic amoebae, pseudopodial activity is central to tissue invasion and feeding strategies.