Why do adult animal sponges lack obvious movement?

Adult sponges lack obvious movement primarily because they do not possess a nervous system or musculature. Unlike many other animals, sponges are primitive, sessile organisms that remain attached to surfaces throughout their adult lives.1

While they do not exhibit conspicuous movement of body parts, sponges are highly functional as animals. They rely on a specialized water-current system consisting of canals and chambers to circulate water, which allows them to filter food and oxygen from their environment. This system is powered by specialized flagellated cells called choanocytes, which generate the necessary currents.234

It is important to note that sponges are only sessile as adults; during their larval stage, they are mobile and swim through the water before eventually settling on a suitable surface to undergo metamorphosis into their adult form.4