Editing Echiura (section)

==Distribution and habitat==
[[Image:Ochetostoma erythrogrammon sujiyumusi.jpg|thumb|''[[Ochetostoma erythrogrammon]]'']]
Echiurans are exclusively marine and the majority of species live in the Atlantic Ocean. They are mostly [[infaunal]], occupying burrows in the seabed, either in the lower [[intertidal zone]] or the shallow [[Neritic zone|subtidal]] (e.g. the genera ''[[Echiurus]]'', ''[[Urechis]]'', and ''[[Ikeda (annelid)|Ikeda]]'').<ref name=Walls/> Others live in holes in coral heads, and in rock crevices. Some are found in deep waters including at [[Abyssal zone|abyssal]] depths; in fact more than half the 70 species in [[Bonelliidae]] live below {{convert|3000|m|ft|-3|abbr=on}}.<ref name=Ruppert>{{cite book |title=Invertebrate Zoology, 7th edition |last1=Ruppert |first1=Edward E. |last2=Fox |first2=Richard, S. |last3=Barnes |first3=Robert D. |year=2004 |publisher=Cengage Learning |isbn=978-81-315-0104-7 |pages=490–495 }}</ref> They often congregate in sediments with high concentrations of organic matter. One species, ''[[Lissomyema mellita]]'', which lives off the southeastern coast of the US, inhabits the tests (exoskeleton) of dead [[sand dollar]]s. When the worm is very small, it enters the test and later becomes too large to leave.<ref>{{cite journal |author=Conn, H.W. |year=1886 |title=Life history of ''Thalassema mellita'' |journal=Stud. Biol. Lab. Johns Hopkins Univ.|pages=1884–1887 }}</ref>

In the 1970s, the spoon worm ''[[Listriolobus pelodes]]'' was found on the [[continental shelf]] off [[Los Angeles]] in numbers of up to 1,500 per square metre (11 square feet) near [[sewage]] outlets.<ref name=Stull/> The burrowing and feeding activities of these worms churned up and aerated the sediment and promoted a balanced [[ecosystem]] with a more diverse [[fauna]] than would otherwise have existed in this heavily [[Pollution|polluted]] area.<ref name=Stull>{{cite journal |author1=Stull, Janet K. |author2=Haydock, C.Irwin |author3=Montagne, David E. |year=1986 |title=Effects of ''Listriolobus pelodes'' (Echiura) on coastal shelf benthic communities and sediments modified by a major California wastewater discharge |journal=[[Estuarine, Coastal and Shelf Science]] |volume=22 |issue=1 |pages=1–17 |doi=10.1016/0272-7714(86)90020-X |bibcode=1986ECSS...22....1S }}</ref>