Editing Bryozoa (section)

== Ecology ==

=== Habitats and distribution ===
Most marine species live in tropical waters at depths less than {{convert|100|m|ft fathom|sp=us}}. However, a few have been found in deep-sea [[Oceanic trench|trenches]],<ref>{{cite book|last=Emiliani|first=C.|author-link=Cesare Emiliani|title=Planet Earth: Cosmology, Geology, & the Evolution of Life & the Environment|publisher=Cambridge University Press|year=1992|pages=[https://archive.org/details/dictionaryofphys00emil/page/488 488–490]|chapter=The Paleozoic|isbn=978-0-19-503652-7|chapter-url=https://books.google.com/books?id=MfAGpVq8gpQC&q=bryozoa%20marine%20tropical&pg=PA489|access-date=2009-08-11|url=https://archive.org/details/dictionaryofphys00emil/page/488}}</ref> especially around [[cold seep]]s, and others near the [[Geographical pole|poles]].<ref name="Jones2006AppliedPaleo">{{cite book|last=Jones|first=R.W.|title=Applied palaeontology|publisher=Cambridge University Press|year=2006|page=116|chapter=Principal fossil groups|isbn=978-0-521-84199-3|chapter-url=https://books.google.com/books?id=KJBKC4qvV8AC&q=bryozoa+marine+tropical&pg=RA5-PA116|access-date=2009-08-11|archive-date=8 March 2023|archive-url=https://web.archive.org/web/20230308183244/https://books.google.com/books?id=KJBKC4qvV8AC&q=bryozoa+marine+tropical&pg=RA5-PA116|url-status=live}}</ref><ref>{{cite journal|last1=Kuklinski|first1=P.|year=2007|title=Comparison of bryozoan assemblages from two contrasting Arctic shelf regions |journal=[[Estuarine, Coastal and Shelf Science]]|volume=73|issue=3–4|pages=835–843|doi=10.1016/j.ecss.2007.03.024|last2=Bader|first2=Beate |bibcode = 2007ECSS...73..835K }}</ref>

The great majority of bryozoans are [[Sessility (zoology)|sessile]]. Typically, sessile bryozoans live on hard substrates including rocks, sand or shells.<ref>{{cite news|last1=Brusca|first1=R|last2=Brusca|first2=G|title=Invertebrates (2nd Edition)|publisher=Sunderland, MA: Sinauer Associates}}</ref> Boring bryozoans leave unique borehole traces after dissolving [[calcium carbonate]] substrates.<ref>{{Cite journal |last1=Johnson |first1=Mildred J. |last2=Lemer |first2=Sarah |last3=Hirose |first3=Masato |last4=Decker |first4=Sebastian H. |last5=Schwaha |first5=Thomas |date=2024-12-31 |title=Ecology of endolithic bryozoans: colony development, growth rates and interactions of species in the genus Immergentia |journal=Zoological Letters |volume=10 |issue=1 |pages=23 |doi=10.1186/s40851-024-00246-9 |doi-access=free |issn=2056-306X |pmc=11686985 |pmid=39736804}}</ref> Encrusting forms are much the commonest of these in shallow seas, but erect forms become more common as the depth increases.<ref name="Jones2006AppliedPaleo" /> An example of incrustation on pebbles and cobbles is found in the diverse Pleistocene bryozoans found in northern Japan, where fossils have been found of single stones covered with more than 20 bryozoan species.{{Sfn|Taylor|2020|p=159}} Sediments with smaller particles, like sand or silt, are usually unsuitable habitat for bryozoans, but tiny colonies have been found encrusting grains of coarse sand.{{Sfn|Taylor|2020|p=164}} Some bryozoan species specialize in colonizing marine algae, seagrasses, and even mangrove roots; the genus ''Amphibiobeania'' lives on the leaves of mangrove trees and is called "amphibious" because it can survive regular exposure to air at low tide.{{Sfn|Taylor|2020|p=162–163}}

There are a variety of "free-living" bryozoans that live un-attached to a substrate. A few forms such as ''[[Cristatella]]'' can move. Lunulitiform cheilostomes are one group of free-living bryozoans with mobile colonies. They form small round colonies un-attached to any substrate; colonies of the genus Selenaria have been observed to "walk" around using setae.{{Sfn|Taylor|2020|p=112–113}} Another cheilostome family, the Cupuladriidae, convergently evolved similarly shaped colonies capable of movement. When observed in an aquarium, Selenaria maculata colonies were recorded to crawl at a speed of one meter per hour, climb over each other, move toward light, and right themselves when turned upside-down.{{Sfn|Taylor|2020|p=79}} Later study of this genus showed that neuroelectrical activity in the colonies increased in correlation with movement toward light sources. It is theorized that the capacity for movement arose as a side effect when colonies evolved longer setae for unburying themselves from sediment.{{Sfn|Taylor|2020|p=79}}
[[File:Alcyonidium (Charleston, South Carolina, 1851).jpg|alt=Watercolor of alcyonidium|thumb|1851 watercolor of ''Alcyonidium'' by Jacques Burkhardt.]]
Other free-living bryozoans are moved freely by waves, currents, or other phenomena. An [[Antarctic]] species, ''Alcyonidium pelagosphaera'', consists of floating colonies. The pelagic species is between {{cvt|5.0 and 23.0|mm}} in diameter, has the shape of a hollow sphere and consists of a single layer of autozooids. It is still not known if these colonies are pelagic their whole life or only represents a temporarily and previously undescribed juvenile stage.<ref name="Jones2006AppliedPaleo" /><ref>{{Cite journal |url=https://link.springer.com/article/10.1007/BF00349118 |title= A pelagic bryozoan from Antarctica|journal=Marine Biology |date=October 1995 |volume=123 |issue=4 |pages=757–762 |doi=10.1007/BF00349118 |access-date=28 August 2017 |archive-date=3 August 2017 |archive-url=https://web.archive.org/web/20170803131921/https://link.springer.com/article/10.1007/BF00349118 |url-status=live |last1=Peck |first1=L. S. |last2=Hayward |first2=P. J. |last3=Spencer-Jones |first3=M. E. |bibcode= 1995MarBi.123..757P|s2cid=83529565 }}</ref> Colonies of the species ''Alcyonidium disciforme'', which is disc-shaped and similarly free-living, inhabit muddy seabeds in the Arctic and can sequester sand grains they have engulfed, potentially using the sand as ballast to turn themselves right-side-up after they have been overturned. Some bryozoan species can form bryoliths, sphere-shaped free-living colonies that grow outward in all directions as they roll about on the seabed.{{Sfn|Taylor|2020|p=114}}

In 2014 it was reported that the bryozoan ''[[Fenestrulina rugula]]'' had become a dominant species in parts of Antarctica. [[Global warming]] has increased the rate of scouring by [[iceberg]]s, and this species is particularly adept at recolonizing scoured areas.<ref>{{Cite news|title='Weedy thing' thrives as Antarctic shores warm|author=Matt McGrath|newspaper=BBC News|url=https://www.bbc.co.uk/news/science-environment-27831958|date=16 June 2014|access-date=16 June 2014|archive-date=17 June 2014|archive-url=https://web.archive.org/web/20140617181747/http://www.bbc.co.uk/news/science-environment-27831958|url-status=live}}</ref>

The phylactolaemates live in all types of freshwater environment – lakes and ponds, rivers and streams, and estuaries<ref name="MassardGeimer2008FreshwaterBryoDiversity" /> – and are among the most abundant sessile freshwater animals.<ref name="WoodLore2005PhylactolaemateMolPhylo">{{cite book|last=Wood|first=T.S.|author2=Lore M.|title=Bryozoan Studies 2004: Proceedings of the 13th International Bryozoology Association|editor=Moyano, H. I. |editor2=Cancino, J.M. |editor3=Wyse-Jackson, P.N.|publisher=Taylor & Francis Group|location=London|year=2005|pages=361–367|chapter=The higher phylogeny of phylactolaemate bryozoans inferred from 18S ribosomal DNA sequences|chapter-url=http://bryotechnologies.com/pdf/18S_rDNA.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://bryotechnologies.com/pdf/18S_rDNA.pdf |archive-date=2022-10-09 |url-status=live|access-date=2009-08-24}}</ref> Some ctenostomes are exclusively freshwater while others prefer brackish water but can survive in freshwater.<ref name="MassardGeimer2008FreshwaterBryoDiversity" /> Scientists' knowledge of freshwater bryozoan populations in many parts of the world is incomplete, even in some parts of Europe. It was long thought that some freshwater species occurred worldwide, but since 2002 all of these have been split into more localized species.<ref name="MassardGeimer2008FreshwaterBryoDiversity" />

Bryozoans grow in [[cloning|clonal]] colonies. A larval Bryozoan settles on a hard substance and produces a colony asexually through budding. These colonies can grow thousands of individual zooids in a relatively short period of time. Even though colonies of zooids grow through asexual reproduction, Bryozoans are hermaphrodites and new colonies can be formed through sexual reproduction and the generation of free swimming larvae. When colonies grow too large, however, they can split in two. This is the only case where asexual reproduction results in a new colony separate from its predecessor. Most colonies are stationary. Indeed, these colonies tend to be settled on immobile substances such as sediment and coarse substances. There are some colonies of freshwater species such as ''[[Cristatella|Cristatella mucedo]]'' that are able to move slowly on a creeping foot.<ref>{{cite web |last1=Ramel |first1=Gordon |date=2020-03-05 |title=Bryozoans: The Fascinating Colonies Of Phylum Ectoprocta |url=https://www.earthlife.net/inverts/bryozoa.html |access-date=2022-05-19 |website=Earthlife |archive-date=27 March 2022 |archive-url=https://web.archive.org/web/20220327220537/https://www.earthlife.net/inverts/bryozoa.html |url-status=live }}</ref>

=== Interactions with non-human organisms ===
[[File:Membranipora membranacea.jpg|thumb|Lacelike ''[[Membranipora membranacea]]'']]
Marine species are common on [[coral reef]]s, but seldom a significant proportion of the total [[biomass]]. In temperate waters, the skeletons of dead colonies form a significant component of shell gravels, and live ones are abundant in these areas.<ref name="MargulisSchwartz1998FiveKingdomsBryozoa" /> The marine lace-like bryozoan ''[[Membranipora membranacea]]'' produces spines in response to predation by several species of [[nudibranch|sea slug]]s (nudibranchs).<ref>{{cite journal|last1=Iyengar|first1=E.V.|year=2002|title=Specificity of cues inducing defensive spines in the bryozoan Membranipora membranacea|journal=Marine Ecology Progress Series|volume=225|pages=205–218|url=http://cat.inist.fr/?aModele=afficheN&cpsidt=13449426|access-date=2009-08-18|doi=10.3354/meps225205|last2=Harvell|first2=CD|bibcode=2002MEPS..225..205I|doi-access=free|archive-date=26 January 2012|archive-url=https://web.archive.org/web/20120126225336/http://cat.inist.fr/?aModele=afficheN&cpsidt=13449426|url-status=live}}</ref> Other predators on marine bryozoans include fish, [[sea urchin]]s, [[pycnogonid]]s, [[crustacean]]s, [[mite]]s<ref>{{cite book|last=Hayward|first=P. J.|author2=Ryland, J.S.|title=Cyclostome bryozoans: keys and notes for the identification of the species|page=27|chapter=Predators|chapter-url=https://books.google.com/books?id=cAsVAAAAIAAJ&q=Bryozoa%20predator%20prey&pg=PA27|access-date=2009-08-18|isbn=978-90-04-07697-6|year=1985|publisher=Brill Archive|archive-date=8 March 2023|archive-url=https://web.archive.org/web/20230308183245/https://books.google.com/books?id=cAsVAAAAIAAJ&q=Bryozoa%20predator%20prey&pg=PA27|url-status=live}}</ref> and [[starfish]].<ref>{{cite journal|last1=Day|first1=R.W.|date=January 1981|title=Predation by ''Patiria miniata'' (Asteroidea) on bryozoans|journal=Oecologia|volume=51|issue=3|pages=300–309|doi=10.1007/BF00540898|pmid=28310012|last2=Osman|first2=R.W.|s2cid=19976956|bibcode=1981Oecol..51..300D}}</ref> In general marine [[echinoderms]] and [[molluscs]] eat masses of zooids by gouging pieces of colonies, breaking their mineralized "houses", while most [[arthropod]] predators on bryozoans eat individual zooids.<ref>{{cite book|last=McKinney|first=F.K.|author2=Taylor, P.D.|author3=Lidgard, S.|title=Predator-prey interactions in the fossil record|editor=Kelley, P.H.|editor2=Kowalewski, M.|editor3=Hansen, T.A.|publisher=Springer|year=2003|pages=239–246|chapter=Predation on Bryozoans and its Reflection in the Fossil Record|isbn=978-0-306-47489-7|chapter-url=https://books.google.com/books?id=bVlYBhq5hNYC&q=%22Predation%20on%20Bryozoans%20and%20its%20Reflection%20in%20the%20Fossil%20Record%22&pg=PA239|access-date=2009-08-18|archive-date=8 March 2023|archive-url=https://web.archive.org/web/20230308183233/https://books.google.com/books?id=bVlYBhq5hNYC&q=%22Predation%20on%20Bryozoans%20and%20its%20Reflection%20in%20the%20Fossil%20Record%22&pg=PA239|url-status=live}}</ref>

In freshwater, bryozoans are among the most important [[filter feeder]]s, along with [[sponge]]s and [[mussel]]s.<ref>{{cite journal|last=Wood|first=T.S.|date=October 2006|title=Freshwater Bryozoans of Thailand (Ectoprocta and Entoprocta)|journal=The Natural History Journal of Chulalongkorn University|volume=6|issue=2|pages=83–119|url=http://www.wright.edu/~tim.wood/documents/2006_ThaiBryos_000.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.wright.edu/~tim.wood/documents/2006_ThaiBryos_000.pdf |archive-date=2022-10-09 |url-status=live|access-date=2009-08-24}}</ref> Freshwater bryozoans are attacked by many predators, including snails, insects, and fish.<ref name="CallaghanKarlson2002SummerDormancy">{{cite journal|last1=Callaghan|first1=T.P.|date=June 2002|title=Summer dormancy as a refuge from mortality in the freshwater bryozoan ''Plumatella emarginata''|journal=Oecologia|volume=132|issue=1|pages=51–59|doi=10.1007/s00442-002-0946-0|pmid=28547286|last2=R.|first2=Karlson|s2cid=19925846|bibcode=2002Oecol.132...51C}}</ref>

In [[Thailand]] the [[introduced species]] ''[[Pomacea canaliculata]]'' (golden apple snail), which is generally a destructive [[herbivore]], has wiped out phylactolaemate populations wherever it has appeared. ''P. canaliculata'' also preys on a common freshwater gymnolaemate, but with less devastating effect. Indigenous snails do not feed on bryozoans.<ref name="predation_golden">{{cite journal|last=Wood|first=T.S.|date=May 2006|title=Heavy Predation on Freshwater Bryozoans by the Golden Apple Snail, ''Pomacea canaliculata''|journal=Natural History Journal of Chulalongkorn University|volume=6|issue=1|pages=31–36|url=http://www2.biology.sc.chula.ac.th/web%20of%20NHJCU%20PDF/6-1,31-36.pdf|access-date=2009-08-18|archive-url=https://web.archive.org/web/20111006013213/http://www2.biology.sc.chula.ac.th/web%20of%20NHJCU%20PDF/6-1,31-36.pdf|archive-date=6 October 2011|url-status=dead}}</ref>

Several species of the [[hydroid (zoology)|hydroid]] family [[Zancleidae]] have symbiotic relationships with bryozoans, some of which are beneficial to the hydroids while others are [[parasite|parasitic]]. Modifications appear in the shapes of some these hydroids, for example smaller tentacles or encrustation of the roots by bryozoans.<ref>{{cite journal|last=Puce|first=S.|year=2007|title=Symbiotic relationships between hydroids and bryozoans|journal=International Symbiosis Society Congress Number 5|volume=44|issue=1–3|pages=137–143|url=http://cat.inist.fr/?aModele=afficheN&cpsidt=18888422|access-date=2009-08-18|archive-date=26 January 2012|archive-url=https://web.archive.org/web/20120126215431/http://cat.inist.fr/?aModele=afficheN&cpsidt=18888422|url-status=live}}</ref> The bryozoan ''[[Alcyonidium nodosum]]'' protects the [[whelk]] ''[[Burnupena papyracea]]'' against predation by the powerful and voracious [[rock lobster]] ''[[Jasus lalandii]]''. While whelk shells encrusted by the bryozoans are stronger than those without this reinforcement, chemical defenses produced by the bryozoans are probably the more significant deterrent.<ref>{{cite journal|last1=Gray|first1=C.A.|date=December 2005 |title=A symbiotic shell-encrusting bryozoan provides subtidal whelks with chemical defence against rock lobsters|journal=African Journal of Marine Science|volume=27|issue=3|pages=549–556| doi = 10.2989/18142320509504115|last2=McQuaid|first2=CD|last3=Davies-Coleman|first3=MT |bibcode=2005AfJMS..27..549G |s2cid=84531235}}</ref>

[[File:Bryolith (Banc d'Arguin, Mauritania).jpg|thumb|Mauritanian bryolith formed by circumrotatory growth of the bryozoan species ''[[Acanthodesia commensale]]'']]
In the [[Banc d'Arguin]] offshore [[Mauritania]] the species ''[[Acanthodesia commensale]]'', which is generally growing attached to gravel and hard-substrate, has formed a [[symbiosis|facultative symbiotic relationship]] with [[hermit crabs]] of the species ''Pseudopagurus cf. granulimanus'' resulting in egg-size structures known as bryoliths.<ref>{{cite journal|last1=Klicpera|first1=André|last2=Taylor|first2=Paul D.|last3=Westphal|first3=Hildegard|s2cid=15841444|title=Bryoliths constructed by bryozoans in symbiotic associations with hermit crabs in a tropical heterozoan carbonate system, Golfe d'Arguin, Mauritania|journal=Marine Biodiversity|date=30 July 2013|volume=43|issue=4|pages=429–444|doi=10.1007/s12526-013-0173-4|bibcode=2013MarBd..43..429K |url=https://doi.pangaea.de/10.1594/PANGAEA.836168|access-date=19 August 2019|archive-date=11 January 2020|archive-url=https://web.archive.org/web/20200111231258/https://doi.pangaea.de/10.1594/PANGAEA.836168|url-status=live}}</ref> Nucleating on an empty gastropod shell, the bryozoan colonies form multilamellar skeletal crusts that produce spherical encrustations and extend the living chamber of the hermit crab through helicospiral tubular growth.

Some phylactolaemate species are intermediate hosts for a group of [[myxozoa]] that have also been found to cause [[proliferative kidney disease]], which is often fatal in [[salmonid]] fish,<ref name="AndersonCanningOkamura2004BryozoanHostsForPKX">{{cite journal|last1=Anderson|first1=C.|year=1999|title=Molecular data implicate bryozoans as hosts for PKX (Phylum Myxozoa) and identify a clade of bryozoan parasites within the Myxozoa|journal=Parasitology|volume=119|issue=6|pages=555–561|url=http://cat.inist.fr/?aModele=afficheN&cpsidt=1203412|access-date=2009-08-18|doi=10.1017/S003118209900520X|pmid=10633916|last2=Canning|first2=E.U.|last3=Okamura|first3=B.|s2cid=2851575|archive-date=26 January 2012|archive-url=https://web.archive.org/web/20120126223846/http://cat.inist.fr/?aModele=afficheN&cpsidt=1203412|url-status=live}}</ref> and has severely reduced wild fish populations in Europe and North America.<ref name="MassardGeimer2008FreshwaterBryoDiversity" />

''[[Membranipora membranacea]]'', whose colonies feed and grow exceptionally fast in a wide range of current speeds, was first noticed in the [[Gulf of Maine]] in 1987 and quickly became the most abundant organism living on [[kelp]]s.<ref name="Pratt2008WhereFlowRight" /> This [[invasive species|invasion]] reduced the kelp population by breaking their fronds,<ref name="RuppertFoxBarnesBryozoa" /> so that its place as the dominant "vegetation" in some areas was taken by another invader, the large [[alga]] ''[[Codium fragile]] tomentosoides''.<ref name="Pratt2008WhereFlowRight" /> These changes reduced the area of habitat available for local fish and invertebrates. ''M. membranacea'' has also invaded the northwest coast of the US.<ref name="RuppertFoxBarnesBryozoa" /> A few freshwater species have been also found thousands of kilometers from their native ranges. Some may have been transported naturally as statoblasts. Others more probably were spread by humans, for example on imported water plants or as stowaways on ships.<ref name="WoodOkamura1999Asajirella" />

=== Interaction with humans ===
[[Fish farms]] and hatcheries have lost stock to [[proliferative kidney disease]], which is caused by one or more [[myxozoan]]s that use bryozoans as alternate hosts.<ref name="AndersonCanningOkamura2004BryozoanHostsForPKX" />

Some fishermen in the [[North Sea]] have had to find other work because of a form of [[eczema]] (a skin disease) known as "[[Dogger Bank itch]]",<ref name="Jones2006AppliedPaleo" /> caused by contact with bryozoans that have stuck to nets and lobster pots.<ref>{{cite journal|last=Clin|first=B.|title=Professional photosensitive eczema of fishermen by contact with bryozoans: disabling occupational dermatosis|journal=International Maritime Health|volume=59|issue=1–4|pages=1–4|url=http://www.imh.mug.edu.pl/attachment/attachment/4761/2008t4.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.imh.mug.edu.pl/attachment/attachment/4761/2008t4.pdf |archive-date=2022-10-09 |url-status=live|access-date=2009-08-18|pmid=19227737|year=2008}}</ref>

Marine bryozoans are often responsible for [[biofouling]] on ships' hulls, on docks and marinas, and on offshore structures. They are among the first colonizers of new or recently cleaned structures.<ref name="MargulisSchwartz1998FiveKingdomsBryozoa">{{cite book|last=Margulis|first=L.|author-link=Lynn Margulis|author2=Schwartz K.V.|title=Five kingdoms: an illustrated guide to the phyla of life on earth|publisher=Elsevier|year=1998|page=[https://archive.org/details/fivekingdomsillu00marg_0/page/335 335]|chapter=Bryozoa|isbn=978-0-7167-3027-9|chapter-url=https://books.google.com/books?id=9IWaqAOGyt4C&q=bryozoa+ectoprocta+fouling|access-date=2009-08-20|url=https://archive.org/details/fivekingdomsillu00marg_0/page/335}}</ref> Freshwater species are occasional nuisances in water pipes, drinking water purification equipment, sewage treatment facilities, and the cooling pipes of power stations.<ref name="MassardGeimer2008FreshwaterBryoDiversity" /><ref>{{cite journal|last1=Wood|first1=T.S.|date=February 1999|title=Biofouling of wastewater treatment plants by the freshwater bryozoan, ''Plumatella vaihiriae''|journal=Water Research|volume=33|issue=3|pages=609–614|doi=10.1016/S0043-1354(98)00274-7|last2=Marsh|first2=Terrence G}}</ref>

A group of chemicals called [[bryostatin]]s can be extracted from the marine bryozoan ''[[Bugula neritina]]''. In 2001 pharmaceutical company [[GPC Biotech]] licensed bryostatin 1 from [[Arizona State University]] for commercial development as a treatment for cancer. GPC Biotech canceled development in 2003, saying that bryostatin 1 showed little effectiveness and some toxic side effects.<ref>{{cite web|url=http://www.marinebiotech.org/bryostatin.html|archive-url=https://web.archive.org/web/20070509175548/http://www.marinebiotech.org/bryostatin.html|url-status=dead|archive-date=9 May 2007|title=Bryostatin 1|date=19 June 2006|access-date=2009-08-20}}</ref> In January 2008 a [[clinical trial]] was submitted to the United States [[National Institutes of Health]] to measure the safety and effectiveness of Bryostatin 1 in the treatment of [[Alzheimer's disease]]. However, no participants had been recruited by the end of December 2008, when the study was scheduled for completion.<ref>{{cite web|url=http://clinicaltrials.gov/ct2/show/results/NCT00606164|title=Safety, Efficacy, Pharmacokinetics, and Pharmacodynamics Study of bryostatin 1 in Patients With Alzheimer's Disease|date=19 August 2009|publisher=National Institutes of Health|access-date=2009-08-20|archive-date=13 June 2011|archive-url=https://web.archive.org/web/20110613200451/http://clinicaltrials.gov/ct2/show/results/NCT00606164|url-status=live}}</ref> More recent work shows it has positive effects on cognition in patients with Alzheimer's disease with few side effects.<ref>{{cite journal | pmc=5438479 | year=2017 | last1=Nelson | first1=T. J. | last2=Sun | first2=M. K. | last3=Lim | first3=C. | last4=Sen | first4=A. | last5=Khan | first5=T. | last6=Chirila | first6=F. V. | last7=Alkon | first7=D. L. | title=Bryostatin Effects on Cognitive Function and PKCɛ in Alzheimer's Disease Phase IIA and Expanded Access Trials | journal=Journal of Alzheimer's Disease | volume=58 | issue=2 | pages=521–535 | doi=10.3233/JAD-170161 |doi-access=free | pmid=28482641 }}</ref> About {{convert|1000|kg|lb}} of bryozoans must be processed to extract {{convert|1|g|oz|frac=32}} of bryostatin, As a result, synthetic equivalents have been developed that are simpler to produce and apparently at least as effective.<ref>{{cite journal|last1=Wender|first1=P.A.|date=20 November 2002|title=The Practical Synthesis of a Novel and Highly Potent Analogue of Bryostatin|journal=Journal of the American Chemical Society|volume=124|issue=46|pages=13648–13649|doi=10.1021/ja027509+|pmid=12431074|last2=Baryza|first2=JL|last3=Bennett|first3=CE|last4=Bi|first4=FC|last5=Brenner|first5=SE
|last6=Clarke|first6=MO|last7=Horan|first7=JC|last8=Kan|first8=C|last9=Lacôte|first9=E|bibcode=2002JAChS.12413648W | display-authors = 8}}</ref>
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== Anatomy ==
[[File:Costazia costazi.jpg|thumb|''[[Costazia costazi]]'', a [[coralline]] bryozoan]]
Bryozoan skeletons grow in a variety of shapes and patterns: mound-shaped, lacy fans, branching twigs, and even corkscrew-shaped. Their [[skeleton]]s have numerous tiny openings, each of which is the home of a minute animal called a '''zooid'''. They also have a [[body cavity|coelomate]] body with a looped alimentary canal or gut, opening at the mouth and terminating at the [[anus]]. They feed with a specialized, [[cilia]]ted structure called a [[lophophore]], which is a crown of [[tentacle]]s surrounding the mouth. Their diet consists of small microorganisms, including [[diatom]]s and other unicellular [[algae]]. In turn, bryozoans are preyed on by grazing organisms such as [[sea urchin]]s and fish. Bryozoans do not have any defined respiratory, or circulatory systems due to their small size. However, they do have a simple nervous system and a hydrostatic skeletal system. Several studies have been undertaken on the crystallography of bryozoan skeletons, revealing a complex fabric suite of oriented [[calcite]] or [[aragonite]] crystallites within an organic matrix – see for example Hall ''et al.'' (2002).

[[File:Lophophores bryozoan.jpg|thumb|right240px|bryozoan lophophores]]
The tentacles of the bryozoans are ciliated, and the beating of the [[cilia]] creates a powerful current of water which drives water together with entrained food particles (mainly phytoplankton) towards the mouth. The gut is U-shaped, and consists of a [[pharynx]] which passes into the [[esophagus]], followed by the [[stomach]], which has three parts: the [[cardia]], the [[caecum]], and the [[pylorus]]. The pylorus leads to an intestine and a short [[rectum]] terminating at the anus, which opens outside the [[lophophore]]. In some groups, notably some ctenostomes, a specialized [[gizzard]] may be formed from the proximal part of the cardia. Gut and lophophore are the principal components of the [[polypide]]. Cyclical degeneration and regeneration of the polypide is characteristic of marine bryozoans. After the final polypide degeneration, the skeletal aperture of the feeding zooid may become sealed by the secretion of a terminal [[Septum (marine biology)|diaphragm]]. In many bryozoans only the zooids within a few generations of the growing edge are in an actively feeding state; older, more proximal zooids (e.g. in the interiors of bushy colonies) are usually dormant.

[[File:Freshwater Bryozoan234.JPG|thumb|left|Freshwater bryozoan]]
Because of their small size, bryozoans have no need of a blood system. Gaseous exchange occurs across the entire surface of the body, but particularly through the tentacles of the lophophore.

Bryozoans can reproduce both sexually and asexually. All bryozoans, as far as is known, are [[hermaphroditic]] (meaning they are both male and female). [[Asexual reproduction]] occurs by budding off new zooids as the colony grows, and is the main way by which a colony expands in size. If a piece of a bryozoan colony breaks off, the piece can continue to grow and will form a new colony. A colony formed this way is composed entirely of [[Cloning|clones]] (genetically identical individuals) of the first animal, which is called the '''ancestrula'''.

One species of bryozoan, ''Bugula neritina'', is of current interest as a source of [[cytotoxicity|cytotoxic]] chemicals, [[bryostatin]]s, under clinical investigation as anti-cancer agents.

== Fossils ==
[[File:07PaleoFTb15.JPG|thumb|Twig-like bryozoan fossils, Upper [[Ordovician]], near Brookville, Indiana.]]
[[File:Prasopora.JPG|thumb|''Prasopora'', a trepostome bryozoan from the [[Ordovician]] of Iowa.]]
[[File:BrownBodies.jpg|thumb|A section through ''Prasopora'' showing "brown bodies" in many of the zooecia; [[Ordovician]] of Iowa.]]
[[File:OilShaleFossilsEstonia.jpg|thumb|Bryozoans in an Ordovician [[oil shale]], northern [[Estonia]].]]
[[File:Bryozoa Hallopora1.jpg|thumb|Detail of [[Hallopora]] fossil specimen on display at [[National Museum of Natural History|Smithsonian]], Washington, DC]]
[[Fossil]] bryozoans are found in rocks beginning in the [[Early Ordovician]] as part of the [[Ordovician radiation]]. They were often major components of Ordovician seabed communities and, like modern-day bryozoans, played an important role in [[sediment]] stabilization and binding, as well as providing sources of food for other [[benthic]] organisms. During the [[Mississippian]] (354 to 323 million years ago) bryozoans were so common that their broken skeletons form entire [[limestone]] beds. Bryozoan fossil record comprises more than 1,000 described species. It is plausible that the Bryozoa existed in the [[Cambrian]] but were soft-bodied or not preserved for some other reason; perhaps they evolved from a [[phoronid]]-like ancestor at about this time.

Bryozoans are important members of sclerobiont (organisms which dwell on hard substrates such as shells and rocks) communities in the fossil record and in the Recent. For a review of sclerobiont evolution, history and ecology, see Taylor & Wilson (2003).

Most fossil bryozoans have mineralized skeletons. The skeletons of individual zooids vary from tubular to box-shaped and contain a terminal aperture from which the [[lophophore]] is protruded to feed. No pores are present in the great majority of Ordovician bryozoans, but skeletal evidence shows that [[epithelia]] were continuous from one zooid to the next.

With regard to the bryozoan groups lacking mineralized skeletons, the [[statoblasts]] of freshwater [[phylactolaemates]] have been recorded as far back as the [[Permian]], and the [[ctenostome]] fossils date from the [[Triassic]].

One of the most important events during bryozoan evolution was the acquisition of a calcareous skeleton and the related change in the mechanism of tentacle protrusion. The rigidity of the outer body walls allowed a greater degree of zooid contiguity and the evolution of massive, multiserial colony forms.

== Classification ==
The bryozoans were formerly considered to contain two subgroups: the ''ectoprocta'' and the ''[[entoprocta]]'', based on the similar bodyplans and mode of life of these two groups. (Some researchers also included the [[Cycliophora]], which are thought to be closely related to the entoprocta.) However, the ectoprocta are ''coelomate'' (possessing a [[body cavity]]) and their embryos undergo [[radial cleavage]], while the entoprocta are ''acoelemate'' and undergo [[spiral cleavage]]. Molecular studies are ambiguous about the exact position of the entoprocta, but do not support a close relationship with the ectoprocta. For these reasons, the entoprocta are now considered a phylum of their own.<ref>{{cite book|author = James W. Valentine|title = On the origins of phyla |year = 2004|publisher = University of Chicago Press}}</ref> The removal of the 150 species of entoprocta leaves ''bryozoa'' synonymous with ''ectoprocta''; some authors have adopted the latter name for the group, but the majority continue to use the former.

The closest relations of the bryozoans appear to be the [[brachiopod]]s. The sister group to this clade is still unclear but this seems most likely to be the [[phoronid]]s.
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