Editing Bryozoa (section)

==== Feeding zooids ====
{{Annotated image | align=right | caption=A generalized autozooid<ref name="RuppertFoxBarnesBryozoa" />
| image=Ectoproct generalized 01.png
| width=280 | height=400 | image-width=156 | image-left=52
|annotations=
{{Annotation|30|108|[[Pharynx]]}}
{{Annotation|30|128|Invert}}
{{Annotation|15|160|Retractor muscle}}
{{Annotation|30|205|[[Ovary]]}}
{{Annotation|15|243|Protective covering}}
{{Annotation|200|20|Lophophore's tentacles}}
{{Annotation|180|98|[[Ganglion]]}}
{{Annotation|180|118|[[Anus]]}}
{{Annotation|195|188|[[Coelom]] (body cavity)}}
{{Annotation|195|228|Stomach }}
{{Annotation|195|262|[[Testis]] }}
{{Annotation|195|280|Funiculus }}
{{Annotation|15|330|{{legend2|border=solid 1px silver|yellow|{{=}} [[Digestive tract]]}}}}
{{Annotation|160|330|{{legend2|border=solid 1px silver|lime|{{=}} [[Gonad]]s}}}}
{{Annotation|15|370|{{legend2|border=solid 1px silver|#a500a5|{{=}} Retractor muscle}}}}
{{Annotation|160|370|{{legend2|border=solid 1px silver|#808000|{{=}} Outer covering}}}}
}}
The most common type of zooid is the feeding autozooid, in which the polypide bears a "crown" of hollow tentacles called a [[lophophore]], which captures food particles from the water.<ref name="Doherty2001EctoproctaInAnderson" /> In all colonies a large percentage of zooids are autozooids, and some consist entirely of autozooids, some of which also engage in reproduction.<ref name="McKinneyJackson">{{cite book|last=McKinney|first=F.K.|author2=Jackson, J.B.C.|title=Bryozoan evolution|publisher=University of Chicago Press|year=1991|pages=1–13|chapter=Bryozoans as modular machines|isbn=978-0-226-56047-2|chapter-url=https://books.google.com/books?id=TMnsG36wHoIC&q=Avicularia+bryozoa&pg=PA7|access-date=2009-07-29|archive-date=8 March 2023|archive-url=https://web.archive.org/web/20230308183241/https://books.google.com/books?id=TMnsG36wHoIC&q=Avicularia+bryozoa&pg=PA7|url-status=live}}</ref>

The basic shape of the "crown" is a full circle. Among the [[Phylactolaemata|freshwater bryozoans]] ([[Phylactolaemata]]) the crown appears U-shaped, but this impression is created by a deep dent in the rim of the crown, which has no gap in the fringe of tentacles.<ref name="RuppertFoxBarnesBryozoa" /> The sides of the tentacles bear fine hairs called [[cilia]], whose beating drives a water current from the tips of the tentacles to their bases, where it exits. Food particles that collide with the tentacles are trapped by [[mucus]], and further cilia on the inner surfaces of the tentacles move the particles towards the mouth in the center.<ref name="RuppertFoxBarnesLophophorataGen"/> The method used by ectoprocts is called "upstream collecting", as food particles are captured before they pass through the field of cilia that creates the feeding current. This method is also used by [[phoronid]]s, [[brachiopod]]s and [[pterobranch]]s.<ref>{{cite journal|last1=Riisgård|first1=H.U.|year=2000|title=Downstream collecting in ciliary suspension feeders: the catch-up principle|journal=Marine Ecology Progress Series|volume=207|pages=33–51|url=https://www.int-res.com/articles/meps/207/m207p033.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.int-res.com/articles/meps/207/m207p033.pdf |archive-date=2022-10-09 |url-status=live|access-date=12 September 2009|doi=10.3354/meps207033|last2=Nielsen|first2=C|last3=Larsen|first3=PS|bibcode=2000MEPS..207...33R|doi-access=free}}</ref>

The lophophore and mouth are mounted on a flexible tube called the "invert", which can be turned inside-out and withdrawn into the polypide,<ref name="RuppertFoxBarnesBryozoa" /> rather like the finger of a rubber glove; in this position the lophophore lies inside the invert and is folded like the spokes of an umbrella. The invert is withdrawn, sometimes within 60{{nbsp}}[[millisecond]]s, by a pair of retractor muscles that are anchored at the far end of the cystid. Sensors at the tips of the tentacles may check for signs of danger before the invert and lophophore are fully extended. Extension is driven by an increase in internal fluid pressure, which species with flexible exoskeletons produce by contracting circular muscles that lie just inside the body wall,<ref name="RuppertFoxBarnesBryozoa" /> while species with a membranous sac use circular muscles to squeeze this.<ref name="Nielsen2001InEncOfLifeSci" /> Some species with rigid exoskeletons have a flexible membrane that replaces part of the exoskeleton, and transverse muscles anchored on the far side of the exoskeleton increase the fluid pressure by pulling the membrane inwards.<ref name="RuppertFoxBarnesBryozoa" /> In others there is no gap in the protective skeleton, and the transverse muscles pull on a flexible sac which is connected to the water outside by a small pore; the expansion of the sac increases the pressure inside the body and pushes the invert and lophophore out.<ref name="RuppertFoxBarnesBryozoa" /> In some species the retracted invert and lophophore are protected by an operculum ("lid"), which is closed by muscles and opened by fluid pressure. In one [[class (biology)|class]], a hollow lobe called the "epistome" overhangs the mouth.<ref name="RuppertFoxBarnesBryozoa" />

The gut is U-shaped, running from the mouth, in the center of the lophophore, down into the animal's interior and then back to the [[anus]], which is located on the invert, outside and usually below the lophophore.<ref name="RuppertFoxBarnesBryozoa" /> A network of strands of [[mesothelium]] called "funiculi" ("little ropes")<ref name="RanHouDictFuniculus">{{cite book|title=Random House Dictionary|publisher=Random House|chapter=funiculus|chapter-url=http://dictionary.reference.com/browse/funiculus|access-date=2009-08-02|archive-date=13 May 2010|archive-url=https://web.archive.org/web/20100513073724/http://dictionary.reference.com/browse/funiculus|url-status=live}}</ref> connects the mesothelium covering the gut with that lining the body wall. The wall of each strand is made of mesothelium, and surrounds a space filled with fluid, thought to be blood.<ref name="RuppertFoxBarnesBryozoa" /> A colony's zooids are connected, enabling autozooids to share food with each other and with any non-feeding heterozooids.<ref name="RuppertFoxBarnesBryozoa" /> The method of connection varies between the different classes of bryozoans, ranging from quite large gaps in the body walls to small pores through which nutrients are passed by funiculi.<ref name="RuppertFoxBarnesBryozoa" /><ref name="Nielsen2001InEncOfLifeSci" />

There is a nerve ring round the pharynx (throat) and a [[ganglion]] that serves as a brain to one side of this. Nerves run from the ring and ganglion to the tentacles and to the rest of the body.<ref name="RuppertFoxBarnesBryozoa" /> Bryozoans have no specialized sense organs, but [[cilia]] on the tentacles act as sensors. Members of the [[genus]] ''[[Bugula]]'' [[phototropism|grow towards the sun]], and therefore must be able to detect light.<ref name="RuppertFoxBarnesBryozoa" /> In colonies of some species, signals are transmitted between zooids through nerves that pass through pores in the body walls, and coordinate activities such as feeding and the retraction of lophophores.<ref name="RuppertFoxBarnesBryozoa" />

The solitary individuals of ''Monobryozoon'' are autozooids with pear-shaped bodies. The wider ends have up to 15 short, muscular projections by which the animals anchor themselves to sand or gravel<ref>{{cite book|last=Hayward|first=P.J.|title=Ctenostome Bryozoans|publisher=Linnean Society of London|year=1985|series=Synopses of the British fauna|pages=106–107|chapter=Systematic part|isbn=978-90-04-07583-2|chapter-url=https://books.google.com/books?id=HgwVAAAAIAAJ&q=monobryozoon&pg=PA106|access-date=2009-08-02|archive-date=8 March 2023|archive-url=https://web.archive.org/web/20230308183239/https://books.google.com/books?id=HgwVAAAAIAAJ&q=monobryozoon&pg=PA106|url-status=live}}</ref> and pull themselves through the sediments.<ref>{{cite book|last=Giere|first=O.|title=Meiobenthology|publisher=Springer-Verlag|year=2009|edition=2nd|page=227|chapter=Tentaculata|isbn=978-3-540-68657-6|chapter-url=https://books.google.com/books?id=an9ncYOxkUoC&q=monobryozoon&pg=PA227|access-date=2009-08-02|archive-date=8 March 2023|archive-url=https://web.archive.org/web/20230308183241/https://books.google.com/books?id=an9ncYOxkUoC&q=monobryozoon&pg=PA227|url-status=live}}</ref>