pseudopode

Pseudópode, or pseudopod, is a temporary cytoplasmic projection of a cell. It arises from the actin cytoskeleton and is used for locomotion and feeding in many amoeboid cells and several protists. Pseudopodia are dynamic and rapidly extend, shorten, or retract as the cell moves or captures prey. They are distinct from fixed surface protrusions such as cilia or flagella and from non-protrusive changes in cell shape.

Formation and mechanics: Extension begins with local actin polymerization at the plasma membrane, pushing the membrane outward and drawing cytoplasm into a protruding lobe. Adhesion to the substrate provides traction. Retraction involves cytoskeletal contraction and the drawing of the trailing cytoplasm toward the cell body. Through pseudopodia, cells can engulf food particles by phagocytosis or trap prey in nets.

Types include lobopodia (broad, blunt projections typical of many amoebae), filopodia (slender, threadlike extensions), reticulopodia (net-like nets seen in some foraminiferans), and axopodia (long, stiff projections supported by microtubules in heliozoans). The particular morphology reflects cytoskeletal organization and ecological needs.

Pseudopodia are also involved in immune responses, for example in macrophages that extend pseudopodia to phagocytose pathogens. They are commonly studied in protist biology and cell motility to understand the mechanics of amoeboid movement and phagocytosis. In laboratory conditions, model organisms such as Amoeba species and Dictyostelium discoideum are used to study pseudopod dynamics.