Editing Bryozoa (section)

=== Feeding and excretion ===
Most species are [[filter feeder]]s that sieve small particles, mainly [[phytoplankton]] (microscopic floating plants), out of the water.<ref name="RuppertFoxBarnesBryozoa" /> The freshwater species ''[[Plumatella emarginata]]'' feeds on [[diatom]]s, [[green algae]], [[cyanobacteria]], non-[[photosynthetic]] bacteria, [[dinoflagellate]]s, [[rotifer]]s, [[protozoa]], small [[nematode]]s, and microscopic [[crustacean]]s.<ref name="CallaghanKarlson2002SummerDormancy" /> While the currents that bryozoans generate to draw food towards the mouth are well understood, the exact method of capture is still debated. All species also flick larger particles towards the mouth with a tentacle, and a few capture [[zooplankton]] (planktonic animals) by using their tentacles as cages. In addition the tentacles, whose surface area is increased by [[microvilli]] (small hairs and pleats), absorb [[organic compound]]s dissolved in the water.<ref name="RuppertFoxBarnesBryozoa" /> Unwanted particles may be flicked away by tentacles or shut out by closing the mouth.<ref name="RuppertFoxBarnesBryozoa" /> A study in 2008 showed that both encrusting and erect colonies fed more quickly and grew faster in gentle than in strong currents.<ref name="Pratt2008WhereFlowRight">{{cite journal|last=Pratt|first=M.C.|year=2008|title=Living where the flow is right: How flow affects feeding in bryozoans|journal= Integrative and Comparative Biology|volume=48|issue=6|pages=808–822|doi=10.1093/icb/icn052|pmid=21669834  |doi-access=free|url=https://scholarworks.smith.edu/context/bio_facpubs/article/1297/viewcontent/Living_where_the_flow_is_right.pdf}}</ref>

In some species the first part of the stomach forms a muscular [[gizzard]] lined with [[chitin]]ous teeth that crush armored prey such as [[diatom]]s. Wave-like [[peristalsis|peristaltic]] contractions move the food through the stomach for digestion. The final section of the stomach is lined with [[cilia]] (minute hairs) that compress undigested solids, which then pass through the [[intestine]] and out through the [[anus]].<ref name="RuppertFoxBarnesBryozoa" />

There are no [[nephridia]] ("little kidneys") or other [[excretory system|excretory]] organs in bryozoa,<ref name="Doherty2001EctoproctaInAnderson" /> and it is thought that [[ammonia]] [[molecular diffusion|diffuses]] out through the body wall and lophophore.<ref name="RuppertFoxBarnesBryozoa" /> More complex waste products are not excreted but accumulate in the [[polypide]], which degenerates after a few weeks. Some of the old polypide is recycled, but much of it remains as a large mass of dying cells containing accumulated wastes, and this is compressed into a "brown body". When the degeneration is complete, the cystid (outer part of the animal) produces a new polypide, and the brown body remains in the [[coelom]], or in the stomach of the new polypide and is expelled next time the animal [[defecate]]s.<ref name="RuppertFoxBarnesBryozoa" />