 Although adult sponges are fundamentally sessile animals, some marine and freshwater species can move across the sea bed at speeds of 1 – 4 mm (0.039 – 0.157 in) per day, as a result of amoeba-like movements of pinacocytes and other cells. A few species can contract their whole bodies, and many can close their oscula and ostia. Juveniles drift or swim freely, while adults are stationary.
