Editing Polychaete (section)

==Ecology==
[[File:Alvinella pompejana01.jpg|thumb| The [[Pompeii worm]]  lives at great depths by hydrothermal vents at temperatures up to 80 °C]]
[[File:Hesiocaeca methanicola noaa.jpg|thumb| ''[[Hesiocaeca methanicola]]'' lives at great depths on [[methane ice]]]]
[[File:Lamellibrachia luymesi1.png|thumb| The cold seep tube worm  ''[[Lamellibrachia]]'' can live over 250 years]]
[[File:Eunice aphroditois.jpg|thumb| The predatory [[Bobbit worm]]]]

Polychaetes are predominantly marine, but many species also live in freshwater, and a few in terrestrial environments.<ref>[https://www.mdpi.com/1424-2818/13/2/98 Annelids in Extreme Aquatic Environments: Diversity, Adaptations and Evolution]</ref> They are extremely variable in both form and lifestyle, and include a few taxa that swim among the [[plankton]] or above the [[abyssal plain]]. Most burrow or build tubes in the sediment, and some live as [[commensal]]s.  A few species, roughly 80 (less than 0.5% of species), are parasitic.<ref name=":0">{{Cite journal |last1=Martin |first1=Daniel |last2=Nygren |first2=Arne |last3=Cruz-Rivera |first3=Edwin |date=2017-06-01 |title=Proceraea exoryxae sp. nov. (Annelida, Syllidae, Autolytinae), the first known polychaete miner tunneling into the tunic of an ascidian |journal=PeerJ |language=en |volume=5 |pages=e3374 |doi=10.7717/peerj.3374 |pmid=28584710 |pmc=5457667 |issn=2167-8359 |doi-access=free }}</ref><ref name=":1">{{Cite book |date=1998 |chapter=SYMBIOTIC POLYCHAETES: REVIEW OF KNOWN SPECIES |chapter-url=https://www.taylorfrancis.com/chapters/edit/10.1201/b12646-22/symbiotic-polychaetes-review-known-species-martin-britayev |title=Oceanography and Marine Biology: An Annual Review |language=en |pages=225–254 |doi=10.1201/b12646-22|doi-broken-date=1 November 2024 | hdl=10261/39328| hdl-access=free|last1=Martin |first1=Daniel |last2=Britayev |first2=Temir A. |publisher=CRC Press |isbn=9780429210600 }}</ref> These include both [[ectoparasites]] and [[endoparasites]]. Ectoparasitic polychaetes feed on skin, blood, and other secretions, and some are adapted to bore through hard, usually calcerous surfaces, such as the shells of mollusks.<ref name=":1" /> These "boring" polychaetes may be parasitic, but may be opportunistic or even obligate symbionts (commensals).<ref>{{Cite journal |last1=Abe |first1=Hirokazu |last2=Hoshino |first2=Osamu |last3=Yamada |first3=Kazuyuki |last4=Ogino |first4=Tetsuya |last5=Kawaida |first5=Shun |last6=Sato-Okoshi |first6=Waka |date=2022-06-28 |title=A novel symbiotic relationship between ascidians and a new tunic-boring polychaete (Annelida: Spionidae: Polydora) |url=https://mapress.com/zt/article/view/zootaxa.5159.1.1 |journal=Zootaxa |language=en |volume=5159 |issue=1 |pages=1–22 |doi=10.11646/zootaxa.5159.1.1 |pmid=36095560 |issn=1175-5334|doi-access=free |url-access=subscription }}</ref><ref name=":1" /><ref name=":0" />

The mobile forms ([[Errantia]]) tend to have well-developed sense organs and jaws, while the stationary forms ([[Sedentaria]]) lack them, but may have specialized gills or tentacles used for respiration and deposit or filter feeding, e.g., [[fanworm]]s.
Underwater polychaetes have eversible mouthparts used to capture prey.<ref>{{cite web |url=http://www.mesa.edu.au/friends/seashores/e_complanata.html |title=Bristleworm |work=MESA}}{{self-published source|date=July 2019}}</ref>{{self-published inline|date=July 2019}} A few groups have evolved to live in terrestrial environments, like [[Namanereidinae]] with many terrestrial species, but are restricted to humid areas. Some have even evolved cutaneous invaginations for aerial gas exchange.