Editing Nemertea (section)

== Ecological significance ==
[[File:Nemertea Terrestrial W Java.png|right|thumb|A terrestrial nemertean from West [[Java]]. The animal is {{convert|1.5|cm|in}} long, of which the anterior {{convert|1|cm|in}} is visible.]]
[[File:Geonemertes sp., Mindanao, Philippines - 20110515-02.jpg|right|thumb|A terrestrial ''[[Geonemertes]]'' sp. on a rotting log, from [[Mindanao]] Island, the [[Philippines]]]]
Most nemerteans are marine animals that burrow in sediments, lurk in crevices between shells, stones or the [[holdfast (biology)|holdfast]]s of [[algae]] or [[Sessility (zoology)|sessile]] animals. Some live deep in the open oceans, and have gelatinous bodies. Others build semi-permanent burrows lined with [[mucus]] or produce [[cellophane]]-like tubes. Mainly in the tropics and subtropics, about 12 species appear in freshwater,<ref name="RFB2004FormBodyProboscis" /> and about a dozen species live on land in cool, damp places, for example under rotting logs.<ref name="MooreOverhill2006" />

The terrestrial ''Argonemertes dendyi'' is a native of [[Australia]] but has been found in the [[British Isles]], in [[São Miguel Island|Sao Miguel]] in the [[Azores]], in [[Gran Canaria]], and in a [[lava tube]] at [[Kaumana]] on the [[Hawaii (island)|Island of Hawaii]]. It can build a cocoon, which allows it to avoid desiccation while being transported, and it may be able to build populations quickly in new areas as it is a [[protandrous]] [[hermaphrodite]].<ref name="HowarthMoore1983">{{cite journal|last=Howarth|first=Francis G.|author2=Janet Moore|year=1983|title=The land nemertine ''Argonemertes dendyi'' (Dakin) in Hawaii (Nemertinea: Hoplonemertinea: Prosorhochmidae)|journal=[[Pacific Science]]|volume=37|issue=2|pages=141–144|url=http://scholarspace.manoa.hawaii.edu/bitstream/10125/654/1/v37n2-141-144.pdf|access-date=2011-02-17|archive-url=https://web.archive.org/web/20181104001908/https://scholarspace.manoa.hawaii.edu/bitstream/10125/654/1/v37n2-141-144.pdf|archive-date=2018-11-04|url-status=dead}}</ref> Another terrestrial [[genus]], ''[[Geonemertes]]'', is mostly found in [[Australasian realm|Australasia]] but has species in the [[Seychelles]], widely across the [[Indo-Pacific]], in [[Tristan da Cunha]] in the South Atlantic, in [[Frankfurt]], in the [[Canary Islands]], in [[Madeira]] and in the Azores.<ref name="Gibson"/>  ''[[Geonemertes pelaensis]]'' has been implicated in the decline of native arthropod species on the [[Ogasawara Islands]], where it was [[Introduced species|introduced]] in the 1980s.<ref>{{Cite journal
| last1=Shinobe |first1=S |last2=Uchida |first2=S |last3=Mori |first3=H |last4=Okochi |first4=I |last5=Chiba |first5=S
| title = Declining soil Crustacea in a World Heritage Site caused by land nemertean
| doi = 10.1038/s41598-017-12653-4
| journal = Scientific Reports
|volume=7 |issue=1 |pages=12400 | year = 2017
| pmid = 28963523
| pmc = 5622052
|bibcode=2017NatSR...712400S }}</ref>

Most are [[carnivore]]s, feeding on [[annelid]]s, [[clam]]s and [[crustacean]]s,<ref name="RFB2004NutritionDigestive" /> and may kill annelids of about their own size. They sometimes take fish, both living and dead. Insects and [[myriapod]]s are the only known prey of the two terrestrial species of ''Argonemertes''.<ref name="McDermottRoe1985">{{cite journal|last=McDermott|first=J.|author2=Pamela Roe|year=1985|title=Food, feeding behavior and feeding ecology of nemerteans |journal=[[American Zoologist]] |volume=25|issue=1|pages=113–125|doi=10.1093/icb/25.1.113|doi-access=free}}</ref>
A few nemerteans are [[scavenger]]s,<ref name="RFB2004NutritionDigestive" /> and these generally have good distance [[chemoreception]] ("smell") and are not selective about their prey.<ref name="McDermottRoe1985" /> A few species live [[commensal]]ly inside the [[mantle (mollusc)|mantle]] cavity of molluscs and feed on micro-organisms filtered out by the host.<ref name="Waggoner">{{cite web |url=http://www.ucmp.berkeley.edu/nemertini/nemertini.html |access-date=3 Feb 2011 |title=Introduction to the Nemertini |publisher=[[University of California, Berkeley]] |date=June 13, 2001 |author1=Ben Waggoner |author2=Allen G. Collins |archive-url=https://web.archive.org/web/20101210034443/http://www.ucmp.berkeley.edu/nemertini/nemertini.html |archive-date=10 December 2010 |url-status=dead }}</ref>

Near [[San Francisco]] the nemertean ''[[Carcinonemertes errans]]'' has consumed about 55% of the total egg production of its host, the [[dungeness crab]] ''Metacarcinus magister''. ''C. errans'' is considered a significant factor in the collapse of the dungeness crab fishery.<ref name="McDermottRoe1985" /> Other coastal nemerteans have devastated [[clam]] beds.<ref name="RFB2004FormBodyProboscis" />

The few predators on nemerteans include bottom-feeding fish, some sea birds, a few invertebrates including [[horseshoe crab]]s, and other nemerteans.<ref name="RFB2004FormBodyProboscis" /> Nemerteans' skins secrete toxins that deter many predators, but some crabs may clean nemerteans with one claw before eating them.<ref name="Moore" /> The American ''[[Cerebratulus lacteus]]'' and the South African ''Polybrachiorhynchus dayi'', both called "tapeworms" in their respective localities, are sold as fish bait.<ref name="RFB2004FormBodyProboscis" />