structural:summarization
Filter feeders

Filter feeders are organisms that obtain their food by filtering their, generally aquatic, environment. Many of the protozoa are filter feeders using a range of adaptations including rigid spikes of protoplasm held in the water flow as in the suctoria to various arrangements of beating cillia to direct particles to the mouth including organisms such as Vorticella which have a complex ring of cilia which create a vortex in the flow drafting particles into the oral cavity. Similar feeding techniques are used by the Rotifera and the Ectoprocta. Many aquatic arthropods are filter feeders. Some use rhythmical beating of abdominal limbs to create a water current to the mouth whilst the hairs on the legs trap any particle. Others such as some caddis flies spin fine webs in the water flow to trap particles.