ice worm

{{Short description|Genus of annelid worms}}

{{for|methane ice worms|Hesiocaeca methanicola}}

{{for|US military project|Project Iceworm}}

{{Automatic taxobox

| image = Mesenchytraeus solifugus anterior.png

| image_caption = Mesenchytraeus solifugus

| taxon = Mesenchytraeus

| authority = Eisen, 1878{{cite web |url=http://www.inhs.uiuc.edu/~mjwetzel/EnchytraeidaeNA.html |title=The aphanoneuran and clitellate Annelida occurring in the United States and Canada: families Enchytraeidae and Propappidae |author1=Kathryn A. Coates |author2=Jan M. Locke |author3=Brenda M. Healy |author4=Mark J. Wetzel |publisher=University of Illinois at Urbana-Champaign |accessdate=January 22, 2010 |date=August 26, 2008}}

| type_species =Mesenchytraeus primaevus

| type_species_authority = Eisen, 1878

| subdivision_ranks = Species

| subdivision = See text

}}

Ice worms (also written as ice-worms or iceworms, or also called glacial or glacier worms) are enchytraeid annelids of the genus Mesenchytraeus. The majority of the species in the genus are abundant in gravel beds or the banks of riverine habitats,{{cite book|author=Paula L. Hartzell & Daniel H. Shain|editor =Daniel H. Shain|title =Annelids in Modern Biology|chapter =Glacier Ice Worms|publisher =Wiley-Blackwell|year =2009|page=305|isbn =9780470455197|chapter-url =https://books.google.com/books?id=9HTIa_JMS1UC&pg=PA305}}{{cite journal|author=Brenda Healy & Steve Fend |year=2002|title=The occurrence of Mesenchytraeus (Enchytraeidae: Oligochaeta) in riffle habitats of north-west Subnautica below zero rivers, with description of a new species|journal=Journal of Natural History|volume=36|issue=1|pages=15–23|doi=10.1080/713833842|s2cid=84290342}} but the best-known members of the genus are found in glacial ice. They include the only annelid worms known to spend their entire lives in glacial ice,{{cite journal|doi=10.1002/1097-4687(200012)246:3<192::AID-JMOR3>3.0.CO;2-B|title=Morphologic characterization of the ice worm Mesenchytraeus solifugus|year=2000|last1=Shain|first1=Daniel H.|last2=Carter|first2=Melissa R.|last3=Murray|first3=Kurt P.|last4=Maleski|first4=Karen A.|last5=Smith|first5=Nancy R.|last6=McBride|first6=Taresha R.|last7=Michalewicz|first7=Lisa A.|last8=Saidel|first8=William M.|journal=Journal of Morphology|volume=246|issue=3|pages=192–7|pmid=11077431 |s2cid=30143253 }} and some of the few metazoans to complete their entire life cycle at conditions below {{convert|0|C|F}}.{{cite journal|author=A.H. Farrell, K.A.Hohenstein, & D.H. Shain|year=2004|title=Molecular adaptation in the ice worm, Mesenchytraeus solifugus: divergence of energetic-associated genes.|journal=Journal of Molecular Evolution|volume=59|issue=5|pages=666–673|doi= 10.1007/s00239-004-2658-z|pmid=15693622|bibcode=2004JMolE..59..666F|s2cid=22139929}}

They were discovered in a wide range of environments, which include level snowfields, steep avalanche cones, crevasse walls, glacial rivers and pools, and hard glacier ice. These organisms are unique in that they can simply move between tightly packed ice crystals. They utilize setae, which are small bristles found on the outside of their bodies, to grip the ice and pull themselves along.

File:Ice Worm against Fingernail.jpg

The genus contains 77 species, including the North American glacier ice worm (Mesenchytraeus solifugus) and the Yosemite snow worm (Mesenchytraeus gelidus).{{cite journal|author=Rüdiger M. Schmelz & Rut Collado|year=2012|title=An updated checklist of currently accepted species of Enchytraeidae (Oligochaeta, Annelida)|journal=VTI Agriculture and Forestry Research |volume=357|pages=67–87|url=https://www.researchgate.net/publication/275099637}}{{cite journal|author=Rüdiger M. Schmelz & Rut Collado|year=2015|title=Checklist of taxa of Enchytraeidae (Oligochaeta): an update|journal=Soil Organisms|volume=87|issue=2|pages=149–152|url=http://www.senckenberg.de/files/content/forschung/publikationen/soilorganisms/volume_87_2/7_87-2-08.pdf|access-date=2017-01-23|archive-url=https://web.archive.org/web/20161220045625/http://www.senckenberg.de/files/content/forschung/publikationen/soilorganisms/volume_87_2/7_87-2-08.pdf|archive-date=2016-12-20|url-status=dead}}{{cite journal|author=Qi Shen, Jing Chen, & Zhicai Xie|year=2012|title=Mesenchytraeus monodiverticulus sp. nov. (Annelida: Cliterllata: Enchytraeidae) from Changbai Mountain, with a key to Mesenchytraeus with enlarged chaetae|journal=Proceedings of the Biological Society of Washington|volume=125|issue=3|pages=215–227|doi=10.2988/12-08.1|s2cid=84234028}}

Ice worms eat snow algae and bacteria.{{cite web |title=Ice Worms (Mesenchytraeus solifugus) and Their Habitats on North Cascade Glaciers-North Cascade Glacier Climate Project |url=http://www.nichols.edu/departments/glacier/iceworm.htm |website=North Cascade Glacier Climate Project |access-date=17 July 2021 |date=November 6, 2008|archive-url=https://web.archive.org/web/20090209012557/http://www.nichols.edu/departments/glacier/iceworm.htm |archive-date=2009-02-09 }} They live at zero degrees Celsius (32 degrees Fahrenheit), but if temperatures dip even slightly below that, according to a Washington State University researcher, the worms die.{{cite news |last1=Greenfieldboyce |first1=Nell |title=It's Summer, And That Means The Mysterious Return Of Glacier Ice Worms |url=https://www.npr.org/2021/07/13/1011376403/its-summer-and-that-means-the-mysterious-return-of-glacier-ice-worms |access-date=17 July 2021 |work=NPR |date=July 13, 2021}}