How do choanocytes create water currents inside sponges?

Choanocytes, also known as collar cells, create water currents within sponges through the continuous, rhythmic movement of their flagella.12

Each choanocyte features a flagellum surrounded by a collar of cytoplasm. As these flagella beat, they push water into the choanocyte chambers, generating internal pressure that extends into the excurrent canals. This movement draws water into the sponge through pores (ostia) and moves it along the system of incurrent canals.123

This water-current system is essential for the sponge's survival, as it facilitates filter feeding by allowing the collar to capture food particles such as bacteria and organic debris. The flow is further regulated by the contraction and expansion of pores and the oscula, ensuring that water is expelled with enough force to prevent contamination of the incoming water supply.32