View source for Biology:Caenorhabditis elegans

{{Short description|Free-living species of nematode}}
{{Speciesbox
| image = Adult Caenorhabditis elegans.jpg
| image_caption = An adult hermaphrodite ''C. elegans'' worm
| taxon = Caenorhabditis elegans
| authority = (Maupas, 1900)<ref>
{{Cite journal | last = Maupas | first = É | year = 1900 | title = Modes et formes de reproduction des nématodes | journal = Archives de Zoologie Expérimentale et Générale | volume = 8 | pages = 463–624 }}</ref>
| subdivision_ranks = Subspecies
| subdivision = 
* ''Caenorhabditis elegans'' var. ''Bergerac''<ref>{{cite journal | title = Les modalités de la reproduction et le déterminisme du sexe chez quelques nematodes libres. | vauthors = Nigon V |  journal = Ann. Sci. Nat. Zool. Biol. Anim. | date = 1949 | volume = 11 | pages = 1–132 }}</ref> (for instance strain BO)<ref>{{cite journal | vauthors = Moerman DG, Waterston RH | title = Spontaneous unstable unc-22 IV mutations in C. elegans var. Bergerac | journal = Genetics | volume = 108 | issue = 4 | pages = 859–77 | date = December 1984 | doi = 10.1093/genetics/108.4.859 | pmid = 6096205 | pmc = 1224270 }}</ref>
* ''Caenorhabditis elegans'' var. ''Bristol''<ref>{{cite journal | vauthors = Babity JM, Starr TV, Rose AM | title = Tc1 transposition and mutator activity in a Bristol strain of ''Caenorhabditis elegans'' | journal = Molecular & General Genetics | volume = 222 | issue = 1 | pages = 65–70 | date = June 1990 | pmid = 1978238 | doi = 10.1007/bf00283024 | s2cid = 11275388 }}</ref> (for instance strain N2)<ref>{{cite journal | vauthors = Harris LJ, Rose AM | title = Structural analysis of Tc1 elements in Caenorhabditis elegans var. Bristol (strain N2) | journal = Plasmid | volume = 22 | issue = 1 | pages = 10–21 | date = July 1989 | pmid = 2550981 | doi = 10.1016/0147-619x(89)90031-0 }}</ref>
}}

'''''Caenorhabditis elegans''''' ({{IPAc-en|ˌ|s|iː|n|oʊ|r|æ|b|ˈ|d|aɪ|t|ə|s|_|ˈ|ɛ|l|ə|ɡ|æ|n|s}}{{refn|{{MerriamWebsterDictionary|Caenorhabditis}}}}) is a free-living transparent [[Biology:Nematode|nematode]] about 1&nbsp;mm in length<ref>
{{cite book | last = Wood | first = WB | year = 1988 | title = The Nematode ''Caenorhabditis elegans'' | page = 1 | publisher = [[Organization:Cold Spring Harbor Laboratory Press|Cold Spring Harbor Laboratory Press]] | isbn = 978-0-87969-433-3 }}</ref> that lives in temperate soil environments. It is the [[Biology:Type species|type species]] of its genus.<ref>{{cite journal |doi=10.1111/j.1439-0469.1996.tb00827.x |title=Phylogeny of ''Rhabditis'' subgenus ''Caenorhabditis'' (Rhabditidae, Nematoda) |journal=Journal of Zoological Systematics and Evolutionary Research |volume=34 |issue=4 |pages=217–233 |year=2009 | vauthors = Sudhaus W, Kiontke K |doi-access=free }}</ref> The name is a [[Social:Hybrid word|blend]] of the Greek ''caeno-'' (recent), ''rhabditis'' (rod-like)<ref>καινός (caenos) = new, recent; ῥάβδος (rhabdos) = rod, wand.</ref> and Latin ''elegans'' (elegant). In 1900, Maupas initially named it ''[[Biology:Rhabditidae|Rhabditides]] elegans.'' Osche placed it in the [[Biology:Subgenus|subgenus]] ''Caenorhabditis'' in 1952, and in 1955, Dougherty raised ''Caenorhabditis'' to the status of [[Biology:Genus|genus]].<ref>
{{cite web
 |last=Ferris
 |first=H
 |date=30 November 2013
 |title=''Caenorhabditis elegans''
 |url=http://plpnemweb.ucdavis.edu/nemaplex/Taxadata/G900S2.htm
 |publisher=[[Organization:University of California, Davis|University of California, Davis]]
 |access-date=2013-11-19
 |url-status=dead
 |archive-url=https://web.archive.org/web/20131209003325/http://plpnemweb.ucdavis.edu/nemaplex/taxadata/G900S2.htm
 |archive-date=9 December 2013
 }}</ref>

''C. elegans'' is an unsegmented [[Biology:Pseudocoelomate|pseudocoelomate]] and lacks respiratory or circulatory systems.<ref>{{cite journal| vauthors = Wallace RL, Ricci C, Melone G | title =A cladistic analysis of pseudocoelomate (aschelminth) morphology.|journal=Invertebrate Biology| volume =115| issue =2|date=1996|pages=104–112| doi =10.2307/3227041| jstor =3227041}}</ref> Most of these nematodes are [[Biology:Hermaphrodite|hermaphrodite]]s and a few are males.<ref>{{Cite web | url = http://www.wormbook.org/chapters/www_introsexdetermination/introsexdetermination.html |title=Introduction to sex determination|website=www.wormbook.org|access-date=2017-03-15}}</ref> Males have specialised tails for mating that include spicules.

In 1963, [[Biography:Sydney Brenner|Sydney Brenner]] proposed research into ''C. elegans,'' primarily in the area of neuronal development. In 1974, he began research into the [[Biology:Molecular biology|molecular]] and [[Biology:Developmental biology|developmental biology]] of ''C. elegans'', which has since been extensively used as a model organism.<ref name="ReferenceB">{{cite journal | vauthors = Brenner S | title = The genetics of ''Caenorhabditis elegans'' | journal = Genetics | volume = 77 | issue = 1 | pages = 71–94 | date = May 1974 | doi = 10.1093/genetics/77.1.71 | pmid = 4366476 | pmc = 1213120 }}</ref> It was the first [[Biology:Multicellular organism|multicellular organism]] to have its [[Biology:Whole genome sequencing|whole genome sequenced]], and in 2019<ref name="da freakin nectome"/> it was the first organism to have its [[Connectome|connectome]] (neuronal "wiring diagram") completed.<ref>{{cite journal | vauthors = White JG, Southgate E, Thomson JN, Brenner S | title = The structure of the nervous system of the nematode ''Caenorhabditis elegans'' | journal = Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume = 314 | issue = 1165 | pages = 1–340 | date = November 1986 | pmid = 22462104 | doi = 10.1098/rstb.1986.0056 | bibcode = 1986RSPTB.314....1W | doi-access = free }}</ref><ref name="wormbook">{{cite journal | vauthors = White JG | title = Getting into the mind of a worm--a personal view | journal = WormBook | pages = 1–10 | date = June 2013 | pmid = 23801597 | pmc = 4781474 | doi = 10.1895/wormbook.1.158.1 }}</ref><ref>{{cite magazine  |last=Jabr |first=Ferris | name-list-style = vanc |date=2012-10-02 |title=The Connectome Debate: Is Mapping the Mind of a Worm Worth It? |url=https://www.scientificamerican.com/article/c-elegans-connectome/ |magazine=Scientific American |access-date=2014-01-18}}</ref>

==Anatomy==
[[File:CrawlingCelegans.gif|thumb|300px|right|Movement of wild-type]]
''C. elegans'' is [[Biology:Segmentation|unsegmented]], vermiform, and bilaterally symmetrical. It has a [[Biology:Cuticle|cuticle]] (a tough outer covering, as an [[Biology:Exoskeleton|exoskeleton]]), four main [[Biology:Epidermis (zoology)|epidermal]] cords, and a fluid-filled pseudocoelom (body cavity). It also has some of the same organ systems as larger animals. About one in a thousand individuals is male and the rest are hermaphrodites.<ref>{{cite book | vauthors = Alberts B, Johnson A, Lewis J, Raff M, Roberts K, Walter P | year = 2007 | title = Molecular Biology of the Cell | edition = 5th | page = 1321 | publisher = Garland Science | isbn = 978-0-8153-4105-5 }}</ref> The basic anatomy of ''C. elegans'' includes a mouth, [[Biology:Pharynx|pharynx]], [[Chemistry:Intestine|intestine]], gonad, and [[Biology:Collagen|collagen]]ous cuticle. Like all nematodes, they have neither a circulatory nor a respiratory system. The four bands of muscles that run the length of the body are connected to a neural system that allows the muscles to move the animal's body only as dorsal bending or ventral bending, but not left or right, except for the head, where the four muscle quadrants are wired independently from one another. When a wave of dorsal/ventral muscle contractions proceeds from the back to the front of the animal, the animal is propelled backwards. When a wave of contractions is initiated at the front and proceeds posteriorly along the body, the animal is propelled forwards. Because of this dorsal/ventral bias in body bends, any normal living, moving individual tends to lie on either its left side or its right side when observed crossing a horizontal surface. A set of ridges on the lateral sides of the body cuticle, the alae, is believed to give the animal added traction during these bending motions.

[[File:Caenorhabditis elegans hermaphrodite adult-en.svg|thumb|300px|right|Lateral (left) side of an adult-stage hermaphrodite|alt=Lateral (left) side anatomical diagram of an adult-stage hermaphrodite]]
[[File:C_elegans_tissues.svg|thumb|300px|right| Tissues of an adult ''C. elegans'']]
[[File:C_elegans_cell_and_nucleus_sizes.svg|thumb|300px|right|  Size and morphology of different ''C. elegans'' cells]]

In relation to lipid metabolism, ''C. elegans'' does not have any specialized adipose tissues, a pancreas, a [[Biology:Liver|liver]], or even blood to deliver nutrients compared to mammals. Neutral lipids are instead stored in the intestine, epidermis, and embryos. The [[Biology:Epidermis|epidermis]] corresponds to the mammalian adipocytes by being the main [[Chemistry:Triglyceride|triglyceride]] depot.<ref>{{cite journal | vauthors = Lemieux GA, Ashrafi K | title = Investigating Connections between Metabolism, Longevity, and Behavior in Caenorhabditis elegans | journal = Trends in Endocrinology and Metabolism | volume = 27 | issue = 8 | pages = 586–596 | date = August 2016 | pmid = 27289335 | pmc = 4958586 | doi = 10.1016/j.tem.2016.05.004 }}</ref>

The pharynx is a muscular food pump in the head of ''C. elegans'', which is triangular in cross-section. This grinds food and transports it directly to the intestine. A set of "valve cells" connects the pharynx to the intestine, but how this valve operates is not understood. After digestion, the contents of the intestine are released via the rectum, as is the case with all other nematodes.<ref>{{Cite web|url=http://www.wormbook.org/chapters/www_organformation/organformation.html|title=The ''C. elegans'' pharynx: a model for organogenesis|website=www.wormbook.org|access-date=2017-03-15}}</ref> No direct connection exists between the pharynx and the [[Biology:Excretion|excretory]] canal, which functions in the release of liquid urine.

Males have a single-lobed gonad, a vas deferens, and a tail specialized for mating, which incorporates spicules. Hermaphrodites have two ovaries, oviducts, and [[Biology:Spermatheca|spermatheca]], and a single [[Biology:Uterus|uterus]]. 
[[File:C elegans male.svg|thumb|300px|right|Anatomical diagram of a male ''C. elegans'']]
[[File:C. elegans with pencil for scale.webm|thumb|right|Video of ''C. elegans'' with pencil for scale]]

There are 302 neurons in ''C. elegans,'' approximately one-third of all the cells in the whole body.<ref name="pmid28889277">{{cite journal | vauthors=Soares FA, Fagundez DA, Avila DS | title=Neurodegeneration Induced by Metals in Caenorhabditis elegans | journal=Advances in Neurobiology | volume=18 | pages=55–383 | year=2017 | doi = 10.1007/978-3-319-60189-2_18 | pmid=28889277| isbn=978-3-319-60188-5 }}</ref> Neurons contain dendrites which extend from the cell to receive neurotransmitters, and a [[Biology:Process (anatomy)|process]] that extends to the nerve ring (the "brain") for a synaptic connection between neurons.<ref>Nonet, M. (2004) [https://web.archive.org/web/20150302133204/http://thalamus.wustl.edu/nonetlab/ResearchF/elegans.html About the nematode Caenorhabdtis elegans]</ref> ''C. elegans'' has motor excitatory and inhibitory neurons, known as [[Biology:Cholinergic|cholinergic]] and gabaergic neurons, which simply act as further regulation for the tiny creature. They have no influence on the nervous system besides regulating neuron impulses.<ref>{{Cite journal |doi=10.1895/wormbook.1.12.1|pmid=18050401|pmc=4781215|title=Specification of the nervous system|journal=WormBook|pages=1–19|year=2005|last1=Hobert|first1=Oliver}}</ref>

=== Gut granules ===
[[File:Nematode Caenorhabditis Elegans.jpg|thumb|Caenorhabditis Elegans under a microscope]]
Numerous gut granules are present in the intestine of ''C. elegans'', the functions of which are still not fully known, as are many other aspects of this nematode, despite the many years that it has been studied. These gut granules are found in all of the Rhabditida orders. They are very similar to lysosomes in that they feature an acidic interior and the capacity for [[Biology:Endocytosis|endocytosis]], but they are considerably larger, reinforcing the view of their being storage organelles.
A remarkable feature of the granules is that when they are observed under ultraviolet light, they react by emitting an intense blue [[Biology:Fluorescence|fluorescence]]. Another phenomenon seen is termed 'death fluorescence'. As the worms die, a dramatic burst of blue fluorescence is emitted. This death fluorescence typically takes place in an anterior to posterior wave that moves along the intestine, and is seen in both young and old worms, whether subjected to lethal injury or peacefully dying of old age.

Many theories have been posited on the functions of the gut granules, with earlier ones being eliminated by later findings. They are thought to store zinc as one of their functions. Recent chemical analysis has identified the blue fluorescent material they contain as a glycosylated form of [[Chemistry:Anthranilic acid|anthranilic acid]] (AA). The need for the large amounts of AA the many gut granules contain is questioned. One possibility is that the AA is antibacterial and used in defense against invading pathogens. Another possibility is that the granules provide photoprotection; the bursts of AA fluorescence entail the conversion of damaging UV light to relatively harmless visible light. This is seen a possible link to the [[Chemistry:Melanin|melanin]]–containing melanosomes.<ref>
{{cite journal | vauthors = Coburn C, Gems D | title = The mysterious case of the ''C. elegans'' gut granule: death fluorescence, anthranilic acid and the kynurenine pathway | journal = Frontiers in Genetics | volume = 4 | pages = 151 | year = 2013 | pmid = 23967012 | pmc = 3735983 | doi = 10.3389/fgene.2013.00151 | doi-access = free }}</ref>

== Reproduction ==

The hermaphroditic worm is considered to be a specialized form of self-fertile female, as its [[Biology:Somatic cell|soma]] is female. The hermaphroditic germline produces male gametes first, and lays eggs through its uterus after internal fertilization. Hermaphrodites produce all their [[Biology:Sperm|sperm]] in the L4 stage (150 sperm cells per gonadal arm) and then produce only [[Biology:Oocyte|oocyte]]s. The hermaphroditic gonad acts as an ovotestis with sperm cells being stored in the same area of the gonad as the oocytes until the first oocyte pushes the sperm into the [[Biology:Spermatheca|spermatheca]] (a chamber wherein the oocytes become fertilized by the sperm).<ref>
{{cite journal | vauthors = Nayak S, Goree J, Schedl T | title = fog-2 and the evolution of self-fertile hermaphroditism in ''Caenorhabditis'' | journal = PLOS Biology | volume = 3 | issue = 1 | pages = e6 | date = January 2005 | pmid = 15630478 | pmc = 539060 | doi = 10.1371/journal.pbio.0030006 | doi-access = free }}</ref>

The male can inseminate the hermaphrodite, which will preferentially use male sperm (both types of sperm are stored in the spermatheca). 
[[File:Male Mating.gif|thumb|Once he recognizes a hermaphrodite worm, the male nematode begins tracing the hermaphrodite with his tail until he reaches the vulval region. The male then probes the region with his spicules to locate the vulva, inserts them, and releases sperm.<ref>{{cite journal | vauthors = Loer CM, Kenyon CJ | title = Serotonin-deficient mutants and male mating behavior in the nematode ''Caenorhabditis elegans'' | journal = The Journal of Neuroscience | volume = 13 | issue = 12 | pages = 5407–17 | date = December 1993 | pmid = 8254383 | pmc = 6576401 | doi=10.1523/jneurosci.13-12-05407.1993| doi-access = free }}</ref>]] The sperm of ''C. elegans'' is amoeboid, lacking flagella and acrosomes.<ref>{{cite journal | vauthors = Ma X, Zhao Y, Sun W, Shimabukuro K, Miao L | title = Transformation: how do nematode sperm become activated and crawl? | journal = Protein & Cell | volume = 3 | issue = 10 | pages = 755–61 | date = October 2012 | pmid = 22903434 | pmc = 4875351 | doi = 10.1007/s13238-012-2936-2 }}</ref> When self-inseminated, the wild-type worm lays about 300 eggs. When inseminated by a male, the number of progeny can exceed 1,000. Hermaphrodites do not typically mate with other hermaphrodites. At 20&nbsp;°C, the laboratory strain of ''C. elegans'' (N2) has an average lifespan around 2–3 weeks and a generation time of 3 to 4 days.

''C. elegans'' has five pairs of [[Biology:Autosome|autosome]]s and one pair of [[Biology:Sex chromosome|sex chromosome]]s. Sex in ''C. elegans'' is based on an [[Biology:X0 sex-determination system|X0 sex-determination system]]. Hermaphrodites of ''C. elegans'' have a matched pair of sex chromosomes (XX); the rare males have only one sex chromosome (X0).

=== Sex determination ===
''C. elegans'' are mostly hermaphroditic organisms, producing both sperms and [[Biology:Oocyte|oocyte]]s.<ref name=":7">{{cite journal | vauthors = Starostina NG, Lim JM, Schvarzstein M, Wells L, Spence AM, Kipreos ET | title = A CUL-2 ubiquitin ligase containing three FEM proteins degrades TRA-1 to regulate C. elegans sex determination | journal = Developmental Cell | volume = 13 | issue = 1 | pages = 127–39 | date = July 2007 | pmid = 17609115 | doi = 10.1016/j.devcel.2007.05.008 | pmc = 2064902 }}</ref> Males do occur in the population in a rate of approximately 1 in 200 hermaphrodites, but the two sexes are highly differentiated.<ref name="Haag_2005" /><ref name=":4">{{Cite web|title=Handbook - Male Introduction|url=https://www.wormatlas.org/male/introduction/mainframe.htm|access-date=2021-03-30|website=www.wormatlas.org}}</ref> Males differ from their hermaphroditic counterparts in that they are smaller and can be identified through the shape of their tail.<ref name=":4" /> ''C.elegans'' reproduce through a process called [[Biology:Androdioecy|androdioecy]]. This means that they can reproduce in two ways: either through self-fertilization in hermaphrodites or through hermaphrodites breeding with males. Males are produced through [[Biology:Nondisjunction|non-disjunction]] of the X chromosomes during meiosis. The worms that reproduce through self-fertilization are at risk for high linkage disequilibrium, which leads to lower genetic diversity in populations and an increase in accumulation of [[Biology:Mutation|deleterious]] alleles.<ref name=":3">{{cite journal | vauthors = Frézal L, Félix MA | title = C. elegans outside the Petri dish | journal = eLife | volume = 4 | pages = e05849 | date = March 2015 | pmid = 25822066 | doi = 10.7554/eLife.05849 | pmc = 4373675 | doi-access = free }}</ref> In ''C. elegans'', somatic sex determination is attributed to the ''[[Biology:TRA (gene)|tra-1]]'' gene.<ref name=":5">{{Cite journal|date=1999-08-06|title=The TRA-1A Sex Determination Protein of C. elegans Regulates Sexually Dimorphic Cell Deaths by Repressing the egl-1 Cell Death Activator Gene|journal=Cell|language=en|volume=98|issue=3|pages=317–327|doi=10.1016/S0092-8674(00)81961-3|issn=0092-8674|last1=Conradt|first1=Barbara|last2=Horvitz|first2=H.Robert|pmid=10458607|s2cid=14951719|doi-access=free}}</ref> The ''tra-1'' is a gene within the TRA-1 transcription factor sex determination pathway that is regulated post-transcriptionally and works by promoting female development.<ref name=":5" /> In hermaphrodites (XX), there are high levels of ''tra-1'' activity, which produces the female reproductive system and inhibits male development.<ref name=":7" /><ref name=":5" /> At a certain time in their life cycle, one day before adulthood, hermaphrodites can be identified through the addition of a vulva near their tail. In males (XO), there are low levels of ''tra-1'' activity, resulting in a male reproductive system.<ref name=":5" /> Recent research has shown that there are three other genes, ''fem-1, fem-2, and fem-3,'' that negatively regulate the TRA-1 pathway and act as the final determiner of sex in ''C. elegans''.<ref name=":7" />

==== Evolution ====
The sex determination system in ''C. elegans'' is a topic that has been of interest to scientists for years.<ref name="Haag_2005">{{cite journal | vauthors = Haag ES | title = The evolution of nematode sex determination: C. elegans as a reference point for comparative biology | journal = WormBook: The Online Review of C. Elegans Biology | volume = | issue = | pages = 1–14 | date = December 2005 | pmid = 18050417 | pmc = 4781019 | doi = 10.1895/wormbook.1.120.1 }}</ref> Since they are used as a model organism, any information discovered about the way their sex determination system might have evolved could further the same evolutionary biology research in other organisms. After almost 30 years of research, scientists have begun to put together the pieces in the evolution of such a system.<ref name="Haag_2005" /> What they have discovered is that there is a complex pathway involved that has several layers of regulation.<ref name="Haag_2005" /> The closely related organism ''Caenorhabditis briggsae'' has been studied extensively and its whole genome sequence has helped put together the missing pieces in the evolution of ''C. elegans'' sex determination.<ref name="Haag_2005" /> It has been discovered that two genes have assimilated, leading to the proteins XOL-1 and MIX-1 having an effect on sex determination in ''C. elegans'' as well.<ref name="Haag_2005" /> Mutations in the XOL-1 pathway leads to feminization in ''C. elegans .''<ref>{{cite journal | vauthors = Miller LM, Plenefisch JD, Casson LP, Meyer BJ | title = xol-1: a gene that controls the male modes of both sex determination and X chromosome dosage compensation in C. elegans | language = English | journal = Cell | volume = 55 | issue = 1 | pages = 167–83 | date = October 1988 | pmid = 3167975 | doi = 10.1016/0092-8674(88)90019-0 | s2cid = 5005906 }}</ref> The ''mix-1'' gene is known to hypoactivate the X chromosome and regulates the morphology of the male tail in ''C. elegans.''<ref>{{Cite web|title=mix-1 (gene) - WormBase : Nematode Information Resource|url=https://wormbase.org/species/c_elegans/gene/WBGene00003367#0-9f-10|access-date=2021-04-23|website=wormbase.org}}</ref> Looking at the nematode as a whole, the male and hermaphrodite sex likely evolved from parallel evolution.<ref name="Haag_2005" /> Parallel evolution is defined as similar traits evolving from an ancestor in similar conditions; simply put, the two species evolve in similar ways over time. An example of this would be [[Biology:Marsupial|marsupial]] and [[Biology:Placentalia|placental]] mammals. Scientists have also hypothesized that hermaphrodite asexual reproduction, or "selfing", could have evolved convergently by studying species similar to ''C. elegans''<ref name="Haag_2005" /> Other studies on the sex determination evolution suggest that genes involving sperm evolve at the faster rate than female genes.<ref name=":9">{{cite journal | vauthors = Cutter AD, Ward S | title = Sexual and temporal dynamics of molecular evolution in C. elegans development | journal = Molecular Biology and Evolution | volume = 22 | issue = 1 | pages = 178–88 | date = January 2005 | pmid = 15371532 | doi = 10.1093/molbev/msh267 | doi-access = free }}</ref> However, sperm genes on the X chromosome have reduced evolution rates. Sperm genes have short coding sequences, high codon bias, and disproportionate representation among orphan genes.<ref name=":9" /> These characteristics of sperm genes may be the reason for their high rates of evolution and may also suggest how sperm genes evolved out of hermaphrodite worms. Overall, scientists have a general idea of the sex determination pathway in ''C. elegans'', however, the evolution of how this pathway came to be is not yet well defined.

==Development==
[[File:C._elegans_embryo_development.tif|thumb|right|''C. elegans'' embryonic development]]

=== Embryonic development ===
The fertilized zygote undergoes rotational holoblastic [[Biology:Cleavage (embryo)|cleavage]].

Sperm entry into the oocyte commences formation of an anterior-posterior axis.<ref name="pmid8625834">{{cite journal | vauthors = Goldstein B, Hird SN | title = Specification of the anteroposterior axis in Caenorhabditis elegans | journal = Development | volume = 122 | issue = 5 | pages = 1467–74 | date = May 1996 | pmid = 8625834 | doi = 10.1242/dev.122.5.1467 | url = https://pubmed.ncbi.nlm.nih.gov/8625834/ }}</ref> The sperm [[Biology:Microtubule organizing center|microtubule organizing center]] directs the movement of the sperm [[Biology:Pronucleus|pronucleus]] to the future posterior pole of the embryo, while also inciting the movement of [[Biology:Cell polarity|PAR proteins]], a group of cytoplasmic determination factors, to their proper respective locations.<ref>{{cite book | title=Developmental biology| edition=11th| author=Gilbert SF| year=2016| pages=268| publisher=Sinauer| isbn=9781605354705}}</ref> As a result of the difference in PAR protein distribution, the first cell division is highly [[Biology:Asymmetric cell division|asymmetric]].<ref name="pmid7758115">{{cite journal | vauthors = Guo S, Kemphues KJ | title = par-1, a gene required for establishing polarity in ''C. elegans'' embryos, encodes a putative Ser/Thr kinase that is asymmetrically distributed | journal = Cell | volume = 81 | issue = 4 | pages = 611–20 | date = May 1995 | pmid = 7758115 | doi = 10.1016/0092-8674(95)90082-9 | doi-access = free }}</ref> ''C. elegans'' [[Biology:Embryogenesis|embryogenesis]] is among the best understood examples of asymmetric cell division.<ref name="ReferenceA">{{cite journal | vauthors = Gönczy P, Rose LS | title = Asymmetric cell division and axis formation in the embryo | journal = WormBook | pages = 1–20 | date = October 2005 | pmid = 18050411 | pmc = 4780927 | doi = 10.1895/wormbook.1.30.1 }}</ref>

All cells of the [[Biology:Germline|germline]] arise from a single primordial germ cell, called the ''P4'' cell, established early in [[Biology:Embryogenesis|embryogenesis]].<ref>Kimble J, Crittenden SL. Germline proliferation and its control. 2005 Aug 15. In: WormBook: The Online Review of C. elegans Biology [Internet]. Pasadena (CA): WormBook; 2005-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK19769/</ref><ref name="wormbase0006773">{{cite encyclopedia | title=WBbt:0006773 (anatomy term) | encyclopedia=[[Biology:WormBase|WormBase]] |edition=WS242 |id=WBbt:0006773 |date=May 14, 2014}}</ref> This primordial cell divides to generate two germline precursors that do not divide further until after hatching.<ref name="wormbase0006773"/>

==== Axis formation ====
The resulting daughter cells of the first cell division are called the AB cell (containing PAR-6 and PAR-3) and the P1 cell (containing PAR-1 and PAR-2). A second cell division produces the ABp and ABa cells from the AB cell, and the EMS and P2 cells from the P1 cell. This division establishes the dorsal-ventral axis, with the ABp cell forming the dorsal side and the EMS cell marking the ventral side.<ref>{{cite book | title=Developmental biology| edition=11th| author=Gilbert SF| year=2016| pages=272| publisher=Sinauer| isbn=9781605354705}}</ref> Through [[Biology:Wnt signaling pathway|Wnt signaling]], the P2 cell instructs the EMS cell to divide along the anterior-posterior axis.<ref name="pmid9288749">{{cite journal | vauthors = Thorpe CJ, Schlesinger A, Carter JC, Bowerman B | title = Wnt signaling polarizes an early ''C. elegans'' blastomere to distinguish endoderm from mesoderm | journal = Cell | volume = 90 | issue = 4 | pages = 695–705 | date = August 1997 | pmid = 9288749 | doi = 10.1016/s0092-8674(00)80530-9 | doi-access = free }}</ref> Through [[Biology:Notch signaling pathway|Notch signaling]], the P2 cell differentially specifies the ABp and ABa cells, which further defines the dorsal-ventral axis. The left-right axis also becomes apparent early in embryogenesis, although it is unclear exactly when specifically the axis is determined. However, most theories of the L-R axis development involve some kind of differences in cells derived from the AB cell.<ref>{{cite journal | vauthors = Pohl C, Bao Z | title = Chiral forces organize left-right patterning in ''C. elegans'' by uncoupling midline and anteroposterior axis | journal = Developmental Cell | volume = 19 | issue = 3 | pages = 402–12 | date = September 2010 | pmid = 20833362 | pmc = 2952354 | doi = 10.1016/j.devcel.2010.08.014 }} {{cite journal | pmid = 3073266 | volume=16 | title=[Quantification of sebaceous excretion in volunteers: influence of chronological age, sex and race] | year=1988 | journal=Med Cutan Ibero Lat Am | pages=439–44 | vauthors=Villares JC, Carlini EA| issue=6 }} {{cite book | title=Developmental biology| edition=11th| author=Gilbert SF| year=2016| pages=269| publisher=Sinauer| isbn=9781605354705}}</ref>

==== Gastrulation ====
Gastrulation occurs after the embryo reaches the 24-cell stage.<ref name="pmid1601187">{{cite journal | vauthors = Skiba F, Schierenberg E | title = Cell lineages, developmental timing, and spatial pattern formation in embryos of free-living soil nematodes | journal = Developmental Biology | volume = 151 | issue = 2 | pages = 597–610 | date = June 1992 | pmid = 1601187 | doi = 10.1016/0012-1606(92)90197-o | url = https://pubmed.ncbi.nlm.nih.gov/1601187 }}</ref> C. elegans are a species of [[Biology:Protostome|protostome]]s, so the blastopore eventually forms the mouth. Involution into the blastopore begins with movement of the [[Biology:Endoderm|endoderm]] cells and subsequent formation of the gut, followed by the P4 germline precursor, and finally the [[Biology:Mesoderm|mesoderm]] cells, including the cells that eventually form the pharynx. Gastrulation ends when [[Biology:Epiboly|epiboly]] of the hypoblasts closes the blastopore.<ref>{{cite book | title=Developmental biology| edition=11th| author=Gilbert SF| year=2016| pages=273| publisher=Sinauer| isbn=9781605354705}}</ref>

=== Post-embryonic development ===
[[File:C_elegans_developmental_stages.svg|thumb|300px|right|   Anatomy and scale of ''C. elegans'' developmental stages]]
[[File:C_elegans_life_cycle.svg|thumb|300px|right|   Life cycle and developmental stages of ''C. elegans'']]

Under environmental conditions favourable for [[Biology:Reproduction|reproduction]], hatched larvae develop through four larval stages - L1, L2, L3, and L4 - in just 3 days at 20&nbsp;°C. When conditions are stressed, as in food insufficiency, excessive population density or high temperature, ''C. elegans'' can enter an alternative third larval stage, L2d, called the [[Biology:Dauer larva|dauer]] stage (''Dauer'' is German for permanent). A specific dauer pheromone regulates entry into the dauer state. This pheromone is composed of similar derivatives of the 3,6-dideoxy sugar, ascarylose. Ascarosides, named after the ascarylose base, are involved in many sex-specific and social behaviors.<ref>{{Cite journal|last1=Ludewig|first1=Andreas H.|last2=Schroeder|first2=Frank C.|date=2013-01-18|title=Ascaroside signaling in C. elegans|journal=WormBook|pages=1–22|doi=10.1895/wormbook.1.155.1|issn=1551-8507|pmc=3758900|pmid=23355522}}</ref> In this way, they constitute a chemical language that ''C. elegans'' uses to modulate various phenotypes. Dauer larvae are stress-resistant; they are thin and their mouths are sealed with a characteristic dauer cuticle and cannot take in food. They can remain in this stage for a few months.<ref name="Introduction to C. Elegans">{{cite web |title=Introduction to ''C. Elegans'' |url=http://avery.rutgers.edu/WSSP/StudentScholars/project/introduction/worms.html |work=C. Elegans as a model organism |publisher=Rutgers University |url-status=dead |archive-url=https://web.archive.org/web/20020818213550/http://avery.rutgers.edu/WSSP/StudentScholars/project/introduction/worms.html |archive-date=2002-08-18 |access-date=August 15, 2014}}</ref><ref>{{Cite web|url=http://www.wormatlas.org/hermaphrodite/introduction/mainframe.htm|title = Handbook - Introduction}}</ref> The stage ends when conditions improve favour further growth of the larva, now moulting into the L4 stage, even though the gonad development is arrested at the L2 stage.<ref>{{Cite web|url=http://www.wormbook.org/chapters/www_dauer/dauer.html|title=Dauer|website=www.wormbook.org|access-date=2018-09-27}}</ref>

Each stage transition is punctuated by a molt of the worm's transparent cuticle. Transitions through these stages are controlled by genes of the heterochronic pathway, an evolutionarily conserved set of regulatory factors.<ref name="pmid20232378">{{cite journal | vauthors = Resnick TD, McCulloch KA, Rougvie AE | title = miRNAs give worms the time of their lives: small RNAs and temporal control in ''Caenorhabditis elegans'' | journal = Developmental Dynamics | volume = 239 | issue = 5 | pages = 1477–89 | date = May 2010 | pmid = 20232378 | pmc = 4698981 | doi = 10.1002/dvdy.22260 }}</ref> Many heterochronic genes code for [[Biology:MicroRNA|microRNA]]s, which repress the expression of heterochronic [[Biology:Transcription factor|transcription factor]]s and other heterochronic miRNAs.<ref name="pmid23962842">{{Cite book | vauthors = Rougvie AE, Moss EG | title = Developmental transitions in ''C. elegans'' larval stages | chapter = Developmental Transitions in C. Elegans Larval Stages | journal = Current Topics in Developmental Biology | series = Developmental Timing | volume = 105 | pages = 153–80 | year = 2013 | publisher = Academic Press | pmid = 23962842 | doi = 10.1016/B978-0-12-396968-2.00006-3 | url = https://pubmed.ncbi.nlm.nih.gov/23962842 | isbn = 9780123969682 }}</ref> miRNAs were originally discovered in ''C. elegans.''<ref name="pmid8252621">{{cite journal | vauthors = Lee RC, Feinbaum RL, Ambros V | title = The C. elegans heterochronic gene lin-4 encodes small RNAs with antisense complementarity to lin-14 | journal = Cell | volume = 75 | issue = 5 | pages = 843–54 | date = December 1993 | pmid = 8252621 | doi = 10.1016/0092-8674(93)90529-y | doi-access = free }}</ref> Important developmental events controlled by heterochronic genes include the division and eventual [[Biology:Syncytium|syncitial]] fusion of the hypodermic seam cells, and their subsequent secretion of the alae in young adults. It is believed that the heterochronic pathway represents an evolutionarily conserved predecessor to [[Biology:Circadian rhythm|circadian clocks]].<ref name="pmid15691769">{{cite journal | vauthors = Banerjee D, Kwok A, Lin SY, Slack FJ | title = Developmental timing in ''C. elegans'' is regulated by kin-20 and tim-1, homologs of core circadian clock genes | journal = Developmental Cell | volume = 8 | issue = 2 | pages = 287–95 | date = February 2005 | pmid = 15691769 | doi = 10.1016/j.devcel.2004.12.006 | doi-access = free }}</ref>

Some nematodes have a fixed, genetically determined number of cells, a phenomenon known as [[Biology:Eutely|eutely]]. The adult ''C. elegans'' hermaphrodite has 959 somatic cells and the male has 1033 cells,<ref>{{Cite journal|last1=Sulston|first1=J.E.|last2=Horvitz|first2=H.R.|date=March 1977|title=Post-embryonic cell lineages of the nematode, Caenorhabditis elegans|url=https://linkinghub.elsevier.com/retrieve/pii/0012160677901580|journal=Developmental Biology|language=en|volume=56|issue=1|pages=110–156|doi=10.1016/0012-1606(77)90158-0|pmid=838129}}</ref><ref>{{Cite journal|last1=Sulston|first1=J.E.|last2=Schierenberg|first2=E.|last3=White|first3=J.G.|last4=Thomson|first4=J.N.|date=November 1983|title=The embryonic cell lineage of the nematode Caenorhabditis elegans|url=https://linkinghub.elsevier.com/retrieve/pii/0012160683902014|journal=Developmental Biology|language=en|volume=100|issue=1|pages=64–119|doi=10.1016/0012-1606(83)90201-4|pmid=6684600}}</ref><ref name="Sammut 385–390">{{Cite journal|last1=Sammut|first1=Michele|last2=Cook|first2=Steven J.|last3=Nguyen|first3=Ken C. Q.|last4=Felton|first4=Terry|last5=Hall|first5=David H.|last6=Emmons|first6=Scott W.|last7=Poole|first7=Richard J.|last8=Barrios|first8=Arantza|date=October 2015|title=Glia-derived neurons are required for sex-specific learning in C. elegans|journal=Nature|language=en|volume=526|issue=7573|pages=385–390|doi=10.1038/nature15700|issn=0028-0836|pmc=4650210|pmid=26469050|bibcode=2015Natur.526..385S}}</ref> although it has been suggested that the number of their intestinal cells can increase by one to three in response to gut microbes experienced by mothers.<ref>{{Cite journal|last1=Ohno|first1=Hayao|last2=Bao|first2=Zhirong|date=2020-11-14|title=Small RNAs couple embryonic developmental programs to gut microbes|journal=bioRxiv|url=http://biorxiv.org/lookup/doi/10.1101/2020.11.13.381830|language=en|doi=10.1101/2020.11.13.381830|s2cid=227060212}}</ref> Much of the literature describes the cell number in males as 1031, but the discovery of a pair of left and right MCM neurons increased the number by two in 2015.<ref name="Sammut 385–390"/>  The number of cells does not change after cell division ceases at the end of the larval period, and subsequent growth is due solely to an increase in the size of individual cells.<ref>{{cite book |title=Invertebrate Zoology |edition=7th |last1=Ruppert |first1=Edward E. |last2=Fox | first2=Richard S. |last3=Barnes |first3=Robert D. | name-list-style = vanc |year=2004 |publisher=Cengage Learning |isbn=978-81-315-0104-7 |page=753 }}</ref>

== Ecology ==
{{Main|Biology:Host microbe interactions in Caenorhabditis elegans}}
The different ''[[Biology:Caenorhabditis|Caenorhabditis]]'' species occupy various nutrient- and bacteria-rich environments. They feed on the bacteria that develop in decaying organic matter ([[Biology:Microbivory|microbivory]]). They possess chemosensory receptors which enable the detection of bacteria and bacterial-secreted metabolites (such as iron siderophores), so that they can migrate towards their bacterial prey.<ref>{{Cite journal |last=Hu |first=Minqi |last2=Ma |first2=Yeping |last3=Chua |first3=Song Lin |date=2024-01-16 |title=Bacterivorous nematodes decipher microbial iron siderophores as prey cue in predator–prey interactions |url=https://pnas.org/doi/10.1073/pnas.2314077121 |journal=Proceedings of the National Academy of Sciences |language=en |volume=121 |issue=3 |doi=10.1073/pnas.2314077121 |issn=0027-8424|doi-access=free |pmc=10801909 }}</ref> Soil lacks enough organic matter to support self-sustaining populations. ''C. elegans'' can survive on a diet of a variety of bacteria, but its wild ecology is largely unknown. Most laboratory strains were taken from artificial environments such as gardens and compost piles. More recently, ''C. elegans'' has been found to thrive in other kinds of organic matter, particularly rotting fruit.<ref>
{{cite journal | vauthors = Félix MA, Braendle C | title = The natural history of ''Caenorhabditis elegans'' | journal = Current Biology | volume = 20 | issue = 22 | pages = R965–9 | date = November 2010 | pmid = 21093785 | doi = 10.1016/j.cub.2010.09.050 | doi-access = free }}</ref>
''C. elegans'' can also ingest pollutants, especially tiny nanoplastics, which could enable the association with antibiotic-resistant bacteria, resulting in the dissemination of nanoplastics and antibiotic-resistant bacteria by ''C. elegans'' across the soil.<ref>{{Cite journal |last1=Chan |first1=Shepherd Yuen |last2=Liu |first2=Sylvia Yang |last3=Wu |first3=Rongben |last4=Wei |first4=Wei |last5=Fang |first5=James Kar-Hei |last6=Chua |first6=Song Lin |date=2023-06-02 |title=Simultaneous Dissemination of Nanoplastics and Antibiotic Resistance by Nematode Couriers |url=https://pubs.acs.org/doi/10.1021/acs.est.2c07129 |journal=Environmental Science & Technology |volume=57 |issue=23 |pages=8719–8727 |language=en |doi=10.1021/acs.est.2c07129 |pmid=37267481 |bibcode=2023EnST...57.8719C |s2cid=259047038 |issn=0013-936X}}</ref> <br />''C. elegans'' can also use different species of [[Biology:Yeast|yeast]], including ''[[Biology:Cryptococcus laurentii|Cryptococcus laurentii]]'' and ''[[Biology:Cryptococcus kuetzingii|C. kuetzingii]]'', as sole sources of food.<ref>{{cite journal | vauthors = Mylonakis E, Ausubel FM, Perfect JR, Heitman J, Calderwood SB | title = Killing of Caenorhabditis elegans by Cryptococcus neoformans as a model of yeast pathogenesis | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 99 | issue = 24 | pages = 15675–80 | date = November 2002 | pmid = 12438649 | pmc = 137775 | doi = 10.1073/pnas.232568599 | bibcode = 2002PNAS...9915675M | doi-access = free }}</ref> Although a [[Earth:Bacterivore|bacterivore]], ''C. elegans'' can be killed by a number of pathogenic bacteria, including human pathogens such as ''[[Medicine:Staphylococcus aureus|Staphylococcus aureus]]'',<ref>{{cite journal | vauthors = Sifri CD, Begun J, Ausubel FM, Calderwood SB | title = Caenorhabditis elegans as a model host for Staphylococcus aureus pathogenesis | journal = Infection and Immunity | volume = 71 | issue = 4 | pages = 2208–17 | date = April 2003 | pmid = 12654843 | pmc = 152095 | doi = 10.1128/IAI.71.4.2208-2217.2003 }}</ref> ''[[Biology:Pseudomonas aeruginosa|Pseudomonas aeruginosa]]'',<ref>{{cite journal | vauthors = Tan MW, Mahajan-Miklos S, Ausubel FM | title = Killing of Caenorhabditis elegans by Pseudomonas aeruginosa used to model mammalian bacterial pathogenesis | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 96 | issue = 2 | pages = 715–20 | date = January 1999 | pmid = 9892699 | pmc = 15202 | doi = 10.1073/pnas.96.2.715 | bibcode = 1999PNAS...96..715T | doi-access = free }}</ref> ''[[Biology:Salmonella enterica|Salmonella enterica]]'' or ''[[Biology:Enterococcus faecalis|Enterococcus faecalis]]''.<ref>{{cite journal | vauthors = Garsin DA, Villanueva JM, Begun J, Kim DH, Sifri CD, Calderwood SB, Ruvkun G, Ausubel FM | display-authors = 6 | title = Long-lived C. elegans daf-2 mutants are resistant to bacterial pathogens | journal = Science | volume = 300 | issue = 5627 | pages = 1921 | date = June 2003 | pmid = 12817143 | doi = 10.1126/science.1080147 | s2cid = 37703980 }}</ref> Pathogenic bacteria can also form biofilms, whose sticky exopolymer matrix could impede ''C. elegans'' motility <ref>{{Cite journal |last1=Chan |first1=Shepherd Yuen |last2=Liu |first2=Sylvia Yang |last3=Seng |first3=Zijing |last4=Chua |first4=Song Lin |date=January 2021 |title=Biofilm matrix disrupts nematode motility and predatory behavior |journal=The ISME Journal |language=en |volume=15 |issue=1 |pages=260–269 |doi=10.1038/s41396-020-00779-9 |pmid=32958848 |pmc=7852553 |bibcode=2021ISMEJ..15..260C |issn=1751-7370}}</ref> and cloaks bacterial quorum sensing chemoattractants from predator detection.<ref>{{Cite journal |last1=Li |first1=Shaoyang |last2=Liu |first2=Sylvia Yang |last3=Chan |first3=Shepherd Yuen |last4=Chua |first4=Song Lin |date=May 2022 |title=Biofilm matrix cloaks bacterial quorum sensing chemoattractants from predator detection |journal=The ISME Journal |language=en |volume=16 |issue=5 |pages=1388–1396 |doi=10.1038/s41396-022-01190-2 |pmid=35034106 |pmc=9038794 |bibcode=2022ISMEJ..16.1388L |issn=1751-7370}}</ref>

Invertebrates such as [[Biology:Millipede|millipede]]s, [[Biology:Insect|insect]]s, isopods, and gastropods can transport dauer larvae to various suitable locations. The larvae have also been seen to feed on their hosts when they die.<ref>
{{cite journal | vauthors = Kiontke K, Sudhaus W | title = Ecology of Caenorhabditis species | journal = WormBook | pages = 1–14 | date = January 2006 | pmid = 18050464 | pmc = 4780885 | doi = 10.1895/wormbook.1.37.1 }}</ref>
<br />Nematodes can survive [[Earth:Desiccation|desiccation]], and in ''C. elegans'', the mechanism for this capability has been demonstrated to be late embryogenesis abundant proteins.<ref>
{{cite journal | vauthors = Gal TZ, Glazer I, Koltai H | title = An LEA group 3 family member is involved in survival of C. elegans during exposure to stress | journal = FEBS Letters | volume = 577 | issue = 1–2 | pages = 21–6 | date = November 2004 | pmid = 15527756 | doi = 10.1016/j.febslet.2004.09.049 | s2cid = 21960486 | doi-access = free }}</ref>
<br />''C. elegans'', as other nematodes, can be eaten by predator nematodes and other omnivores, including some insects.<ref>Elaine R. Ingham [https://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/health/biology/  Soil biology primer] USDA</ref>

The [[Biology:Orsay virus|Orsay virus]] is a virus that affects ''C. elegans'', as well as the [[Biology:Caenorhabditis elegans Cer1 virus|Caenorhabditis elegans Cer1 virus]]<ref>{{Cite journal |doi=10.1101/gr.9.10.924|pmid=10523521|title=Genomic Analysis of ''Caenorhabditis elegans'' Reveals Ancient Families of Retroviral-like Elements|journal=Genome Research|volume=9|issue=10|pages=924–935|year=1999|last1=Bowen|first1=N. J.|doi-access=free}}</ref> and the [[Biology:Caenorhabditis elegans Cer13 virus|Caenorhabditis elegans Cer13 virus]].

; Interactions with fungi
Wild isolates of ''Caenorhabditis elegans'' are regularly found with infections by [[Biology:Microsporidia|Microsporidia]] fungi. One such species, ''[[Biology:Nematocida parisii|Nematocida parisii]]'', replicates in the intestines of ''C. elegans''.<ref>{{cite journal | vauthors = Cuomo CA, Desjardins CA, Bakowski MA, Goldberg J, Ma AT, Becnel JJ, Didier ES, Fan L, Heiman DI, Levin JZ, Young S, Zeng Q, Troemel ER | title = Microsporidian genome analysis reveals evolutionary strategies for obligate intracellular growth | journal = Genome Research | volume = 22 | issue = 12 | pages = 2478–88 | date = December 2012 | pmid = 22813931 | pmc = 3514677 | doi = 10.1101/gr.142802.112 }}</ref>

''[[Biology:Arthrobotrys oligospora|Arthrobotrys oligospora]]'' is the model organism for interactions between fungi and nematodes.<ref>{{Cite journal |doi=10.1080/21501203.2011.562559|title=''Arthrobotrys oligospora'': A model organism for understanding the interaction between fungi and nematodes|journal=Mycology|volume=2|issue=2|pages=59–78|year=2011|last1=Niu|first1=Xue-Mei|last2=Zhang|first2=Ke-Qin | name-list-style = vanc |doi-access=free}}</ref> It is the most common and widespread nematode capturing fungus.

== Use as a model organism ==
{{Further|Biology:History of research on Caenorhabditis elegans}}
[[File:Epigenetic-Regulation-of-Histone-H3-Serine-10-Phosphorylation-Status-by-HCF-1-Proteins-in-C.-pone.0001213.s003.ogv|thumb|Asymmetric cell divisions during early embryogenesis of wild-type ''C. elegans'']]
In 1963, [[Biography:Sydney Brenner|Sydney Brenner]] proposed using ''C. elegans'' as a model organism for the investigation primarily of neural development in animals. It is one of the simplest organisms with a [[Biology:Nervous system|nervous system]]. The neurons do not fire action potentials, and do not express any [[Biology:Voltage-gated sodium channel|voltage-gated sodium channel]]s.<ref>{{cite journal | vauthors = Clare JJ, Tate SN, Nobbs M, Romanos MA | title = Voltage-gated sodium channels as therapeutic targets | journal = Drug Discovery Today | volume = 5 | issue = 11 | pages = 506–520 | date = November 2000 | pmid = 11084387 | doi = 10.1016/S1359-6446(00)01570-1 }}</ref> In the hermaphrodite, this system comprises 302 [[Biology:Neuron|neuron]]s<ref>{{cite journal |bibcode=2007AcPPB..38.2201K |title=Dynamics of the Model of the Caenorhabditis Elegans Neural Network |journal=Acta Physica Polonica B |volume=38 |issue=6 |pages=2201 | vauthors = Kosinski RA, Zaremba M  |year=2007 }}</ref> the pattern of which has been comprehensively mapped,<ref name="da freakin nectome">
{{cite journal
 |title=Whole-animal connectomes of both ''Caenorhabditis elegans'' sexes
 |last1=Cook
 |first1=SJ
 |last2=Jarrell
 |first2=TA
 |last3=Brittin
 |first3=CA
 |last4=Wang
 |first4=Y
 |last5=Bloniarz
 |first5=AE
 |last6=Yakovlev
 |first6=MA
 |last7=Nguyen
 |first7=KCQ
 |last8=Tang
 |first8=Lt-H
 |last9=Bayer
 |first9=EA
 |last10=Duerr
 |first10=JS
 |last11=Bulow
 |first11=HE
 |last12=Hobert
 |first12=O
 |last13=Hall
 |first13=DH
 |last14=Emmons
 |first14=SW
 |journal=Nature
 |date=3 December 2019
 |volume=571
 |issue=7763
 |pages=63–71
 |publisher= US National Library of Medicine, National Institutes of Health 
 |doi=10.1038/s41586-019-1352-7
 |pmc=6889226
 |pmid=31270481
|bibcode=2019Natur.571...63C
 }}</ref> in what is known as a [[Connectome|connectome]],<ref name="Brouillette">{{cite journal |last1=Brouillette |first1=Monique |title=Mapping the brain to understand the mind |journal=Knowable Magazine {{!}} Annual Reviews |date=21 April 2022 |doi=10.1146/knowable-042122-1|doi-access=free |url=https://knowablemagazine.org/article/mind/2022/mapping-brain-understand-mind |language=en}}</ref> and shown to be a [[Small-world network|small-world network]].<ref>{{cite journal | vauthors = Watts DJ, Strogatz SH | title = Collective dynamics of 'small-world' networks | journal = Nature | volume = 393 | issue = 6684 | pages = 440–2 | date = June 1998 | pmid = 9623998 | doi = 10.1038/30918 | bibcode = 1998Natur.393..440W | s2cid = 4429113 }}</ref>

Research has explored the neural and molecular mechanisms that control several behaviors of ''C. elegans'', including [[Physics:Chemotaxis|chemotaxis]], thermotaxis, [[Biology:Mechanotransduction|mechanotransduction]], [[Learning|learning]], [[Memory|memory]], and [[Biology:Mating|mating]] behaviour.<ref>{{cite journal | vauthors = Schafer WR | title = Deciphering the neural and molecular mechanisms of C. elegans behavior | journal = Current Biology | volume = 15 | issue = 17 | pages = R723–9 | date = September 2005 | pmid = 16139205 | doi = 10.1016/j.cub.2005.08.020 |  doi-access = free }}</ref> In 2019 the connectome of the male was published using a technique distinct from that used for the hermaphrodite. The same paper used the new technique to redo the hermaphrodite connectome, finding 1,500 new synapses.<ref>{{cite journal | vauthors = Cook SJ, Jarrell TA, Brittin CA, Wang Y, Bloniarz AE, Yakovlev MA, Nguyen KC, Tang LT, Bayer EA, Duerr JS, Bülow HE, Hobert O, Hall DH, Emmons SW | display-authors = 6 | title = Whole-animal connectomes of both Caenorhabditis elegans sexes | journal = Nature | volume = 571 | issue = 7763 | pages = 63–71 | date = July 2019 | pmid = 31270481 | pmc = 6889226 | doi = 10.1038/s41586-019-1352-7 | bibcode = 2019Natur.571...63C }}</ref>

It has been used as a model organism to study molecular mechanisms in metabolic diseases.<ref name="ReferenceC">{{cite journal | vauthors = Alcántar-Fernández J, Navarro RE, Salazar-Martínez AM, Pérez-Andrade ME, Miranda-Ríos J | title = Caenorhabditis elegans respond to high-glucose diets through a network of stress-responsive transcription factors | journal = PLOS ONE | volume = 13 | issue = 7 | pages = e0199888 | date = 2018 | pmid = 29990370 | pmc = 6039004 | doi = 10.1371/journal.pone.0199888 | bibcode = 2018PLoSO..1399888A | doi-access = free }}</ref> 
Brenner also chose it as it is easy to grow in bulk populations, and convenient for genetic analysis.<ref>{{cite web |last=Avery |first=L |title=Sydney Brenner |url=http://elegans.swmed.edu/Sydney.html |publisher=Southwestern Medical Center |url-status=dead |archive-url=https://web.archive.org/web/20110815143145/http://elegans.swmed.edu/Sydney.html |archive-date=August 15, 2011 }} [http://elegans.som.vcu.edu/Sydney.html Alt. URL] {{Webarchive|url=https://web.archive.org/web/20131208060434/http://elegans.som.vcu.edu/Sydney.html |date=2013-12-08 }}</ref> It is a multicellular [[Biology:Eukaryote|eukaryotic]] organism, yet simple enough to be studied in great detail. The transparency of ''C. elegans'' facilitates the study of [[Biology:Cellular differentiation|cellular differentiation]] and other developmental processes in the intact organism. The spicules in the male clearly distinguish males from females. [[Biology:Strain|Strains]] are cheap to breed and can be frozen. When subsequently thawed, they remain viable, allowing long-term storage.<ref name="ReferenceB"/> Maintenance is easy when compared to other multicellular model organisms. A few hundred nematodes can be kept on a single [[Organization:Agar plate|agar plate]] and suitable growth medium. Brenner described the use of a mutant of ''E. coli'' – OP50. OP50 is a [[Chemistry:Uracil|uracil]]-requiring organism and its deficiency in the plate prevents the overgrowth of bacteria which would obscure the worms.<ref>{{cite journal | last1 = Brenner | first1 = S | year = 1974 | title = The genetics of Caenorhabditis elegans. | journal = Genetics | volume = 77 | issue = 1| pages = 71–94 | doi = 10.1093/genetics/77.1.71 | pmc = 1213120 | pmid = 4366476 }}</ref> The use of OP50 does not demand any major laboratory safety measures, since it is non-pathogenic and easily grown in Luria-Bertani (LB) media overnight.<ref>{{Cite web|url=http://www.wormbook.org/chapters/www_behavior/behavior.html#sec1|title=Behavior|website=www.wormbook.org|access-date=2018-09-26}}</ref>

=== Cell lineage mapping ===
The developmental fate of every single [[Biology:Somatic cell|somatic cell]] (959 in the adult hermaphrodite; 1031 in the adult male) has been mapped.<ref>
{{cite journal | vauthors = Sulston JE, Horvitz HR | title = Post-embryonic cell lineages of the nematode, Caenorhabditis elegans | journal = Developmental Biology | volume = 56 | issue = 1 | pages = 110–56 | date = March 1977 | pmid = 838129 | doi = 10.1016/0012-1606(77)90158-0 }}</ref><ref>
{{cite journal | vauthors = Kimble J, Hirsh D | title = The postembryonic cell lineages of the hermaphrodite and male gonads in Caenorhabditis elegans | journal = Developmental Biology | volume = 70 | issue = 2 | pages = 396–417 | date = June 1979 | pmid = 478167 | doi = 10.1016/0012-1606(79)90035-6 }}</ref> These patterns of cell lineage are largely invariant between individuals, whereas in mammals, cell development is more dependent on cellular cues from the embryo.

As mentioned previously, the first cell divisions of early [[Biology:Embryogenesis|embryogenesis]] in ''C. elegans'' are among the best understood examples of [[Biology:Asymmetric cell division|asymmetric cell division]]s, and the worm is a very popular model system for studying developmental biology.<ref name="ReferenceA"/>

=== Programmed cell death ===
Programmed cell death ([[Biology:Apoptosis|apoptosis]]) eliminates many additional cells (131 in the hermaphrodite, most of which would otherwise become [[Biology:Neuron|neuron]]s); this "apoptotic predictability" has contributed to the elucidation of some [[Biology:Caretaker gene|apoptotic genes]]. Cell death-promoting genes and a single cell-death inhibitor have been identified.<ref>{{cite journal | vauthors = Peden E, Killian DJ, Xue D | title = Cell death specification in C. elegans | journal = Cell Cycle | volume = 7 | issue = 16 | pages = 2479–84 | date = August 2008 | pmid = 18719375 | pmc = 2651394 | doi = 10.4161/cc.7.16.6479 }}</ref>

=== RNA interference and gene silencing ===
[[File:C elegans stained.jpg|thumb|right|Wild-type ''C. elegans'' hermaphrodite stained with the fluorescent dye [[Chemistry:Texas Red|Texas Red]] to highlight the nuclei of all cells]]

[[Biology:RNA interference|RNA interference]] (RNAi) is a relatively straightforward method of disrupting the function of specific genes. [[Biology:Gene silencing|Silencing]] the function of a gene can sometimes allow a researcher to infer its possible function. The nematode can be soaked in, injected with,<ref>{{Cite web|url=https://www.youtube.com/watch?v=Wam-kw4xwZc| archive-url=https://ghostarchive.org/varchive/youtube/20211117/Wam-kw4xwZc| archive-date=2021-11-17 | url-status=live|title=Injection of C. elegans Gonads|last=NIDDK|first=National Institute of Diabetes and Digestive and Kidney Diseases|website=YouTube|date=March 5, 2015|access-date=March 21, 2020}}{{cbignore}}</ref> or fed with genetically [[Biology:Transformation (genetics)|transformed]] bacteria that [[Biology:Gene expression|express]] the double-stranded RNA of interest, the sequence of which complements the sequence of the gene that the researcher wishes to disable.<ref>
{{cite journal | vauthors = Kamath RS, Fraser AG, Dong Y, Poulin G, Durbin R, Gotta M, Kanapin A, Le Bot N, Moreno S, Sohrmann M, Welchman DP, Zipperlen P, Ahringer J | title = Systematic functional analysis of the Caenorhabditis elegans genome using RNAi | journal = Nature | volume = 421 | issue = 6920 | pages = 231–7 | date = January 2003 | pmid = 12529635 | doi = 10.1038/nature01278 | bibcode = 2003Natur.421..231K | hdl = 10261/63159 | s2cid = 15745225 }}</ref>
RNAi has emerged as a powerful tool in the study of functional genomics. ''C. elegans'' has been used to analyse gene functions and claim the promise of future findings in the systematic genetic interactions.<ref>{{cite journal | vauthors = Fortunato A, Fraser AG | title = Uncover genetic interactions in Caenorhabditis elegans by RNA interference | journal = Bioscience Reports | volume = 25 | issue = 5–6 | pages = 299–307 | date = 2005 | pmid = 16307378 | doi = 10.1007/s10540-005-2892-7 | s2cid = 6983519  }}</ref>

Environmental RNAi uptake is much worse in other species of worms in the genus ''Caenorhabditis''. Although injecting RNA into the body cavity of the animal induces [[Biology:Gene silencing|gene silencing]] in most species, only ''C. elegans'' and a few other distantly related nematodes can take up RNA from the bacteria they eat for RNAi.<ref>
{{cite journal | vauthors = Félix MA | title = RNA interference in nematodes and the chance that favored Sydney Brenner | journal = Journal of Biology | volume = 7 | issue = 9 | pages = 34 | date = November 2008 | pmid = 19014674 | pmc = 2776389 | doi = 10.1186/jbiol97 | doi-access = free }}</ref> This ability has been mapped down to a single gene, ''sid-2'', which, when inserted as a [[Biology:Transgene|transgene]] in other species, allows them to take up RNA for RNAi as ''C. elegans'' does.<ref>
{{cite journal | vauthors = Winston WM, Sutherlin M, Wright AJ, Feinberg EH, Hunter CP | title = Caenorhabditis elegans SID-2 is required for environmental RNA interference | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 104 | issue = 25 | pages = 10565–70 | date = June 2007 | pmid = 17563372 | pmc = 1965553 | doi = 10.1073/pnas.0611282104 | bibcode = 2007PNAS..10410565W | doi-access = free }}</ref>

=== Cell division and cell cycle ===
Research into [[Biology:Meiosis|meiosis]] has been considerably simplified since every germ cell nucleus is at the same given position as it moves down the gonad, so is at the same stage in meiosis. In an early phase of meiosis, the oocytes become extremely resistant to radiation and this resistance depends on expression of genes ''rad51'' and ''atm'' that have key roles in recombinational repair.<ref name="pmid11058122">{{cite journal | vauthors = Takanami T, Mori A, Takahashi H, Higashitani A | title = Hyper-resistance of meiotic cells to radiation due to a strong expression of a single recA-like gene in Caenorhabditis elegans | journal = Nucleic Acids Research | volume = 28 | issue = 21 | pages = 4232–6 | date = November 2000 | pmid = 11058122 | pmc = 113154 | doi = 10.1093/nar/28.21.4232 }}</ref><ref name="pmid14646232">{{cite journal | vauthors = Takanami T, Zhang Y, Aoki H, Abe T, Yoshida S, Takahashi H, Horiuchi S, Higashitani A | title = Efficient repair of DNA damage induced by heavy ion particles in meiotic prophase I nuclei of Caenorhabditis elegans | journal = Journal of Radiation Research | volume = 44 | issue = 3 | pages = 271–6 | date = September 2003 | pmid = 14646232 | doi = 10.1269/jrr.44.271 | bibcode = 2003JRadR..44..271T | doi-access = free }}</ref> Gene ''mre-11'' also plays a crucial role in recombinational repair of DNA damage during meiosis.<ref name=Chin>{{cite journal | vauthors = Chin GM, Villeneuve AM | title = C. elegans mre-11 is required for meiotic recombination and DNA repair but is dispensable for the meiotic G(2) DNA damage checkpoint | journal = Genes & Development | volume = 15 | issue = 5 | pages = 522–34 | date = March 2001 | pmid = 11238374 | pmc = 312651 | doi = 10.1101/gad.864101 }}</ref> A study of the frequency of outcrossing in natural populations showed that [[Biology:Selfing|selfing]] is the predominant mode of reproduction in ''C. elegans'', but that infrequent outcrossing events occur at a rate around 1%.<ref name="pmid16005289">{{cite journal | vauthors = Barrière A, Félix MA | title = High local genetic diversity and low outcrossing rate in Caenorhabditis elegans natural populations | journal = Current Biology | volume = 15 | issue = 13 | pages = 1176–84 | date = July 2005 | pmid = 16005289 | doi = 10.1016/j.cub.2005.06.022 | arxiv = q-bio/0508003 | bibcode = 2005q.bio.....8003B | s2cid = 2229622 }}</ref>  Meioses that result in selfing are unlikely to contribute significantly to beneficial genetic variability, but these meioses may provide the adaptive benefit of recombinational repair of DNA damages that arise, especially under stressful conditions.<ref>Bernstein H, Bernstein C (July 2010) "Evolutionary Origin of Recombination during Meiosis," BioScience 60(7), 498-505. https://doi.org/10.1525/bio.2010.60.7.5</ref>

=== Drug abuse and addiction ===
[[Chemistry:Nicotine|Nicotine]] [[Medicine:Substance dependence|dependence]] can also be studied using ''C. elegans'' because it exhibits behavioral responses to nicotine that parallel those of mammals. These responses include acute response, tolerance, withdrawal, and sensitization.<ref>{{cite journal | vauthors = Feng Z, Li W, Ward A, Piggott BJ, Larkspur ER, Sternberg PW, Xu XZ | title = A C. elegans model of nicotine-dependent behavior: regulation by TRP-family channels | journal = Cell | volume = 127 | issue = 3 | pages = 621–33 | date = November 2006 | pmid = 17081982 | pmc = 2859215 | doi = 10.1016/j.cell.2006.09.035 }}</ref>

=== Biological databases ===
As for most model organisms, scientists that work in the field curate a dedicated online database and the [[Biology:WormBase|WormBase]] is that for ''C. elegans''. The WormBase attempts to collate all published information on ''C. elegans'' and other related nematodes. Their website has advertised a reward of $4000 for the finder of a new species of closely related nematode.<ref>{{cite web |title=''Caenorhabditis'' isolation guide |url=http://wormbase.org/external/2007/nematode_isolation_guide/nematode_isolation_guide.html |publisher=[[Biology:WormBase|WormBase]] |access-date=2007-08-30 |url-status=dead |archive-url=https://web.archive.org/web/20071107102752/http://wormbase.org/external/2007/nematode_isolation_guide/nematode_isolation_guide.html |archive-date=November 7, 2007 }} [http://www.briggsae.org/misc/NemaIsolGuide/index.html Alt. URL] {{Webarchive|url=https://web.archive.org/web/20140905134803/http://briggsae.org/misc/NemaIsolGuide/index.html |date=2014-09-05 }}</ref> Such a discovery would broaden research opportunities with the worm.<ref>{{cite journal |doi=10.1126/science.317.5842.1157b |title=Slime for a Dime |journal=Science |volume=317 |issue=5842 |pages=1157b |year=2007 |last1=Dolgin |first1=E. |s2cid=85163742 }}</ref>

=== Ageing ===
''C. elegans'' has been a model organism for research into ageing; for example, the inhibition of an [[Biology:Insulin-like growth factor|insulin-like growth factor]] signaling pathway has been shown to increase adult lifespan threefold;<ref>{{cite journal | vauthors = Wolkow CA, Kimura KD, Lee MS, Ruvkun G | title = Regulation of C. elegans life-span by insulinlike signaling in the nervous system | journal = Science | volume = 290 | issue = 5489 | pages = 147–50 | date = October 2000 | pmid = 11021802 | doi = 10.1126/science.290.5489.147 | bibcode = 2000Sci...290..147W }}</ref><ref>{{cite journal | vauthors = Ewald CY, Landis JN, Porter Abate J, Murphy CT, Blackwell TK | title = Dauer-independent insulin/IGF-1-signalling implicates collagen remodelling in longevity | language = En | journal = Nature | volume = 519 | issue = 7541 | pages = 97–101 | date = March 2015 | pmid = 25517099 | pmc = 4352135 | doi = 10.1038/nature14021 | bibcode = 2015Natur.519...97E }}</ref> while glucose feeding promotes oxidative stress and reduce adult lifespan by a half.<ref name="ReferenceC"/> Similarly, induced degradation of an insulin/IGF-1 receptor late in life extended life expectancy of worms dramatically.<ref>{{Cite journal|last1=Venz|first1=Richard|last2=Pekec|first2=Tina|last3=Katic|first3=Iskra|last4=Ciosk|first4=Rafal|author5-link=Collin Y. Ewald|last5=Ewald|first5=Collin Yvès|date=2021-09-10|editor-last=Leiser|editor-first=Scott F|editor2-last=Kaeberlein|editor2-first=Matt|editor3-last=Alcedo|editor3-first=Joy|title=End-of-life targeted degradation of DAF-2 insulin/IGF-1 receptor promotes longevity free from growth-related pathologies|journal=eLife|volume=10|pages=e71335|doi=10.7554/eLife.71335|pmid=34505574|pmc=8492056|issn=2050-084X |doi-access=free }}</ref> 
Long-lived [[Biology:Mutant|mutant]]s of ''C. elegans'' were demonstrated to be resistant to [[Biology:Oxidative stress|oxidative stress]] and [[Physics:Ultraviolet|UV light]].<ref name="Hyun2008">{{Cite journal |doi=10.1093/nar/gkm1161 |pmc=2275101 |pmid=18203746|title=Longevity and resistance to stress correlate with DNA repair capacity in Caenorhabditis elegans |year=2008 |last1=Hyun |first1=Moonjung |last2=Lee |first2=Jihyun |last3=Lee |first3=Kyungjin |last4=May |first4=Alfred |last5=Bohr |first5=Vilhelm A. |last6=Ahn |first6=Byungchan |journal=Nucleic Acids Research |volume=36 |issue=4 |pages=1380–1389 }}</ref> These long-lived mutants had a higher [[Biology:DNA repair|DNA repair]] capability than wild-type ''C. elegans''.<ref name = Hyun2008/> Knockdown of the [[Biology:Nucleotide excision repair|nucleotide excision repair]] gene Xpa-1 increased sensitivity to UV and reduced the [[Biology:Longevity|life span]] of the long-lived mutants. These findings indicate that [[Biology:DNA damage theory of aging|DNA repair capability underlies longevity]].

The capacity to repair DNA damage by the process of nucleotide excision repair declines with age.<ref>{{Cite journal |doi=10.1186/gb-2007-8-5-r70 |pmc=1929140 |pmid=17472752|title=Decline of nucleotide excision repair capacity in aging Caenorhabditis elegans |year=2007 |last1=Meyer |first1=Joel N. |last2=Boyd |first2=Windy A. |last3=Azzam |first3=Gregory A. |last4=Haugen |first4=Astrid C. |last5=Freedman |first5=Jonathan H. |last6=Van Houten |first6=Bennett |journal=Genome Biology |volume=8 |issue=5 |pages=R70 |doi-access=free }}</ref>

''C. elegans'' exposed to 5mM [[Chemistry:Lithium chloride|lithium chloride]] (LiCl) showed lengthened life spans.<ref>{{cite journal | vauthors = McColl G, Killilea DW, Hubbard AE, Vantipalli MC, Melov S, Lithgow GJ | title = Pharmacogenetic analysis of lithium-induced delayed aging in Caenorhabditis elegans | journal = The Journal of Biological Chemistry | volume = 283 | issue = 1 | pages = 350–7 | date = January 2008 | pmid = 17959600 | pmc = 2739662 | doi = 10.1074/jbc.M705028200 | doi-access = free }}</ref> When exposed to 10μM LiCl, reduced mortality was observed, but not with 1μM.<ref>{{cite journal | vauthors = Zarse K, Terao T, Tian J, Iwata N, Ishii N, Ristow M | title = Low-dose lithium uptake promotes longevity in humans and metazoans | journal = European Journal of Nutrition | volume = 50 | issue = 5 | pages = 387–9 | date = August 2011 | pmid = 21301855 | pmc = 3151375 | doi = 10.1007/s00394-011-0171-x }}</ref>

''C. elegans'' has been instrumental in the identification of the functions of genes implicated in [[Medicine:Alzheimer's disease|Alzheimer's disease]], such as presenilin.<ref>{{cite journal | vauthors = Ewald CY, Li C | title = Understanding the molecular basis of Alzheimer's disease using a Caenorhabditis elegans model system | journal = Brain Structure & Function | volume = 214 | issue = 2–3 | pages = 263–83 | date = March 2010 | pmid = 20012092 | pmc = 3902020 | doi = 10.1007/s00429-009-0235-3 }}</ref> Moreover, extensive research on ''C. elegans'' has identified [[Biology:RNA-binding protein|RNA-binding protein]]s as essential factors during germline and early embryonic development.<ref>{{cite journal | vauthors = Hanazawa M, Yonetani M, Sugimoto A | title = PGL proteins self associate and bind RNPs to mediate germ granule assembly in C. elegans | journal = The Journal of Cell Biology | volume = 192 | issue = 6 | pages = 929–37 | date = March 2011 | pmid = 21402787 | pmc = 3063142 | doi = 10.1083/jcb.201010106 }}</ref>

[[Biology:Telomere|Telomere]]s, the length of which have been shown to correlate with increased lifespan and delayed onset of [[Biology:Senescence|senescence]] in a multitude of organisms, from ''C. elegans''<ref>{{Cite journal|last1=Coutts|first1=Fiona|last2=Palmos|first2=Alish B.|last3=Duarte|first3=Rodrigo R. R.|last4=de Jong|first4=Simone|last5=Lewis|first5=Cathryn M.|last6=Dima|first6=Danai|last7=Powell|first7=Timothy R.|date=March 2019|title=The polygenic nature of telomere length and the anti-ageing properties of lithium|journal=Neuropsychopharmacology|volume=44|issue=4|pages=757–765|doi=10.1038/s41386-018-0289-0|issn=1740-634X|pmc=6372618|pmid=30559463}}</ref><ref>{{Cite journal|last1=Raices|first1=Marcela|last2=Maruyama|first2=Hugo|last3=Dillin|first3=Andrew|last4=Karlseder|first4=Jan|date=September 2005|title=Uncoupling of longevity and telomere length in C. elegans|journal=PLOS Genetics|volume=1|issue=3|pages=e30|doi=10.1371/journal.pgen.0010030|issn=1553-7404|pmc=1200426|pmid=16151516 |doi-access=free }}</ref> to humans,<ref>{{Cite journal|last1=Lulkiewicz|first1=M.|last2=Bajsert|first2=J.|last3=Kopczynski|first3=P.|last4=Barczak|first4=W.|last5=Rubis|first5=B.|date=September 2020|title=Telomere length: how the length makes a difference|journal=Molecular Biology Reports|volume=47|issue=9|pages=7181–7188|doi=10.1007/s11033-020-05551-y|issn=1573-4978|pmc=7561533|pmid=32876842}}</ref> show an interesting behaviour in ''C. elegans.'' While ''C. elegans'' maintains its telomeres in a canonical way similar to other eukaryotes, in contrast ''[[Biology:Drosophila melanogaster|Drosophila melanogaster]]'' is noteworthy in its use of [[Biology:Retrotransposon|retrotransposon]]s to maintain its telomeres,<ref>{{Cite journal|last1=Pardue|first1=Mary-Lou|last2=DeBaryshe|first2=P. G.|date=2011-12-20|title=Retrotransposons that maintain chromosome ends|journal=Proceedings of the National Academy of Sciences of the United States of America|volume=108|issue=51|pages=20317–20324|doi=10.1073/pnas.1100278108|issn=1091-6490|pmc=3251079|pmid=21821789|doi-access=free}}</ref> during [[Biology:Gene knockout|knock-out]] of the [[Biology:Telomerase reverse transcriptase|catalytic subunit of the telomerase (''trt-1'')]] ''C. elegans'' can gain the ability of alternative telomere lengthening (ALT). ''C. elegans'' was the first eukaryote to gain ALT functionality after knock-out of the canonical [[Biology:Telomerase|telomerase]] pathway.<ref>{{Cite journal|last1=Meier|first1=Bettina|last2=Clejan|first2=Iuval|last3=Liu|first3=Yan|last4=Lowden|first4=Mia|last5=Gartner|first5=Anton|last6=Hodgkin|first6=Jonathan|last7=Ahmed|first7=Shawn|date=February 2006|title=trt-1 is the Caenorhabditis elegans catalytic subunit of telomerase|journal=PLOS Genetics|volume=2|issue=2|pages=e18|doi=10.1371/journal.pgen.0020018|issn=1553-7404|pmc=1361356|pmid=16477310 |doi-access=free }}</ref> ALT is also observed in about 10-15% of all clinical cancers.<ref>{{Cite journal|last1=Cesare|first1=Anthony J.|last2=Reddel|first2=Roger R.|date=May 2010|title=Alternative lengthening of telomeres: models, mechanisms and implications|url=https://pubmed.ncbi.nlm.nih.gov/20351727|journal=Nature Reviews. Genetics|volume=11|issue=5|pages=319–330|doi=10.1038/nrg2763|issn=1471-0064|pmid=20351727|s2cid=19224032}}</ref> Thus ''C. elegans'' is a prime candidate for ALT research.<ref>{{Cite journal|last1=Ijomone|first1=Omamuyovwi M.|last2=Miah|first2=Mahfuzur R.|last3=Peres|first3=Tanara V.|last4=Nwoha|first4=Polycarp U.|last5=Aschner|first5=Michael|date=December 2016|title=Null allele mutants of trt-1, the catalytic subunit of telomerase in Caenorhabditis elegans, are less sensitive to Mn-induced toxicity and DAergic degeneration|url=https://pubmed.ncbi.nlm.nih.gov/27593554|journal=Neurotoxicology|volume=57|pages=54–60|doi=10.1016/j.neuro.2016.08.016|issn=1872-9711|pmid=27593554}}</ref><ref>{{Cite journal|last1=Shtessel|first1=Ludmila|last2=Lowden|first2=Mia Rochelle|last3=Cheng|first3=Chen|last4=Simon|first4=Matt|last5=Wang|first5=Kyle|last6=Ahmed|first6=Shawn|date=February 2013|title=Caenorhabditis elegans POT-1 and POT-2 repress telomere maintenance pathways|journal=G3: Genes, Genomes, Genetics|volume=3|issue=2|pages=305–313|doi=10.1534/g3.112.004440|issn=2160-1836|pmc=3564990|pmid=23390606}}</ref><ref>{{Cite journal|last1=Kwon|first1=Mi-Sun|last2=Min|first2=Jaewon|last3=Jeon|first3=Hee-Yeon|last4=Hwang|first4=Kwangwoo|last5=Kim|first5=Chuna|last6=Lee|first6=Junho|last7=Joung|first7=Je-Gun|last8=Park|first8=Woong-Yang|last9=Lee|first9=Hyunsook|date=October 2016|title=Paradoxical delay of senescence upon depletion of BRCA2 in telomerase-deficient worms|journal=FEBS Open Bio|volume=6|issue=10|pages=1016–1024|doi=10.1002/2211-5463.12109|issn=2211-5463|pmc=5055038|pmid=27761361}}</ref> Bayat et al. showed the paradoxical shortening of telomeres during ''[[Biology:Telomerase reverse transcriptase|trt-1]]'' over-expression which lead to near [[Biology:Sterility (physiology)|sterility]] while the worms even exhibited a slight increase in lifespan, despite shortened telomeres.<ref>{{Cite journal|last1=Bayat|first1=Melih|last2=Tanny|first2=Robyn E.|last3=Wang|first3=Ye|last4=Herden|first4=Carla|last5=Daniel|first5=Jens|last6=Andersen|first6=Erik C.|last7=Liebau|first7=Eva|last8=Waschk|first8=Daniel E. J.|date=2020-03-30|title=Effects of telomerase overexpression in the model organism Caenorhabditis elegans|url=https://pubmed.ncbi.nlm.nih.gov/31954861|journal=Gene|volume=732|pages=144367|doi=10.1016/j.gene.2020.144367|issn=1879-0038|pmid=31954861|s2cid=210829489}}</ref>

=== Sleep ===
''C. elegans'' is notable in animal sleep studies as the most primitive organism to display sleep-like states. In ''C. elegans'', a lethargus phase occurs shortly before each [[Biology:Ecdysis|moult]].<ref>{{cite journal | vauthors = Iwanir S, Tramm N, Nagy S, Wright C, Ish D, Biron D | title = The microarchitecture of C. elegans behavior during lethargus: homeostatic bout dynamics, a typical body posture, and regulation by a central neuron | journal = Sleep | volume = 36 | issue = 3 | pages = 385–95 | date = March 2013 | pmid = 23449971 | pmc = 3571756 | doi = 10.5665/Sleep.2456 }}</ref> ''C. elegans'' has also been demonstrated to sleep after exposure to physical stress, including heat shock, UV radiation, and bacterial toxins.<ref>{{cite journal | vauthors = Hill AJ, Mansfield R, Lopez JM, Raizen DM, Van Buskirk C | title = Cellular stress induces a protective sleep-like state in C. elegans | journal = Current Biology | volume = 24 | issue = 20 | pages = 2399–405 | date = October 2014 | pmid = 25264259 | pmc = 4254280 | doi = 10.1016/j.cub.2014.08.040 }}</ref>

=== Sensory biology ===
While the worm has no eyes, it has been found to be sensitive to light due to a third type of light-sensitive animal [[Biology:Photoreceptor protein|photoreceptor protein]], [[Biology:LITE-1|LITE-1]], which is 10 to 100 times more efficient at absorbing light than the other two types of photopigments (opsins and cryptochromes) found in the animal kingdom.<ref>[https://www.livescience.com/56913-new-photoreceptor-found-in-worms.html Teensy, Eyeless Worms Have Completely New Light-Detecting Cells]</ref>

''C. elegans'' is remarkably adept at tolerating acceleration. It can withstand 400,000 [[Physics:G-force|g]]'s, according to geneticists at the University of São Paulo in Brazil. In an experiment, 96% of them were still alive without adverse effects after an hour in an ultracentrifuge.<ref>Scientific American, August 2018, page 14</ref>

=== Spaceflight research ===
''C. elegans'' made news when specimens were discovered to have survived the [[Engineering:Space Shuttle Columbia disaster|Space Shuttle ''Columbia'' disaster]] in February 2003.<ref>
{{cite news
 |date=1 May 2003
 |title=Worms survived Columbia disaster
 |url=http://news.bbc.co.uk/1/hi/sci/tech/2992123.stm
 |work=BBC News
 |access-date=2008-07-11
}}</ref> Later, in January 2009, live samples of ''C. elegans'' from the [[Organization:University of Nottingham|University of Nottingham]] were announced to be spending two weeks on the [[Astronomy:International Space Station|International Space Station]] that October, in a [[Astronomy:Space research|space research]] project to explore the effects of zero gravity on muscle development and physiology. The research was primarily about genetic basis of [[Medicine:Muscle atrophy|muscle atrophy]], which relates to [[Engineering:Spaceflight|spaceflight]] or being bed-ridden, geriatric, or diabetic.<ref>
{{cite news
 |date=17 January 2009
 |title=University sends worms into space
 |url=http://news.bbc.co.uk/1/hi/england/nottinghamshire/7835020.stm
 |work=BBC News
 |access-date=2009-07-09
}}</ref> Descendants of the worms aboard Columbia in 2003 were launched into space on [[Engineering:Space Shuttle Endeavour|''Endeavour'']] for the [[Engineering:STS-134|STS-134]] mission.<ref>{{cite news
 |last1=Klotz
 |first1=I
 |date=16 May 2011
 |title=Legacy Space Worms Flying on Shuttle
 |url=http://news.discovery.com/space/legacy-space-worms-flying-on-shuttle-110516.html
 |work=Discovery News
 |access-date=2011-05-17
 |archive-date=2012-06-16
 |archive-url=https://web.archive.org/web/20120616014937/http://news.discovery.com/space/legacy-space-worms-flying-on-shuttle-110516.html
 |url-status=dead
 }}</ref> Additional experiments on muscle dystrophy during spaceflight were carried on board the ISS starting in 2018.<ref>{{Cite journal |last1=Soni |first1=Purushottam |last2=Anupom |first2=Taslim |last3=Lesanpezeshki |first3=Leila |last4=Rahman |first4=Mizanur |last5=Hewitt |first5=Jennifer E. |last6=Vellone |first6=Matthew |last7=Stodieck |first7=Louis |last8=Blawzdziewicz |first8=Jerzy |last9=Szewczyk |first9=Nathaniel J. |last10=Vanapalli |first10=Siva A. |date=2022-11-07 |title=Microfluidics-integrated spaceflight hardware for measuring muscle strength of Caenorhabditis elegans on the International Space Station |journal=npj Microgravity |volume=8 |issue=1 |pages=50 |doi=10.1038/s41526-022-00241-4 |issn=2373-8065 |pmc=9640571 |pmid=36344513|bibcode=2022npjMG...8...50S }}</ref> It was shown that the genes affecting muscles attachment were expressed less in space. However, it has yet to be seen if this affects muscle strength.

== Genetics ==
=== Genome ===
{{Infobox genome <!-- a.k.a GenomeInfo for short -->
| image = Karyotype of Caenorhabditis elegans.png
| caption = [[Biology:Karyotype|Karyotype]] of ''C. elegans''<br />{{hidden|explanation of colors|Mitotic chromosomes of ''C. elegans''. DNA (red)/ [[Biology:Kinetochore|Kinetochore]]s (green). Holocentric organisms, including ''C. elegans'', assemble diffuse kinetochores along the entire poleward face of each sister chromatid.}}
| taxId = 41 
| ploidy = diploid 
| chromosomes = 5 pairs of autosomes (I, II, III, IV and V) + 1 or 2 sex chromosomes (X<ref>{{cite journal | vauthors = Strome S, Kelly WG, Ercan S, Lieb JD | title = Regulation of the X chromosomes in ''Caenorhabditis elegans'' | journal = Cold Spring Harbor Perspectives in Biology | volume = 6 | issue = 3 | pages = a018366 | date = March 2014 | pmid = 24591522 | pmc = 3942922 | doi = 10.1101/cshperspect.a018366 }}</ref>)
| size = 101.169 Mb (haploid)
| year = 1998
| organelle = mitochondrion 
| organelle-size = 0,01 Mb
| organelle-year = <!-- year of sequencing of organelle -->
}}
[[File:CelegansGoldsteinLabUNC.jpg|thumb|right|''C. elegans'' hermaphrodite]]
''C. elegans'' was the first multicellular organism to have its [[Biology:Whole genome sequencing|whole genome sequenced]]. The sequence was published in 1998,<ref>
{{cite journal |author=The ''C. elegans'' Sequencing Consortium | title = Genome sequence of the nematode ''C. elegans'': a platform for investigating biology | journal = Science | volume = 282 | issue = 5396 | pages = 2012–8 | date = December 1998 | pmid = 9851916 | doi = 10.1126/science.282.5396.2012 | bibcode = 1998Sci...282.2012. }}</ref> although some small gaps were present; the last gap was finished by October 2002. In the run up to the whole genome the ''C. elegans'' Sequencing Consortium/''C. elegans'' Genome Project released several partial scans including Wilson et al. 1994.<ref name="Sadler-1998">{{cite journal | last=Sadler | first=J. Evan | title=Biochemistry and genetics of von Willebrand factor | journal=[[Chemistry:Annual Review of Biochemistry|Annual Review of Biochemistry]] | publisher=Annual Reviews | volume=67 | issue=1 | year=1998 | issn=0066-4154 | doi=10.1146/annurev.biochem.67.1.395 | pages=395–424| pmid=9759493 | doi-access=free }}</ref><ref name="Hahn-2002">{{cite journal | last=Hahn | first=Mark E. | title=Aryl hydrocarbon receptors: diversity and evolution | journal=Chemico-Biological Interactions | publisher=[[Company:Elsevier|Elsevier]] | volume=141 | issue=1–2 | year=2002 | issn=0009-2797 | doi=10.1016/s0009-2797(02)00070-4 | pages=131–160| pmid=12213389 }}</ref><ref name="Bustelo-2000">{{cite journal | last=Bustelo | first=Xosé R. | title=Regulatory and Signaling Properties of the Vav Family | journal=[[Biology:Molecular and Cellular Biology|Molecular and Cellular Biology]] | publisher=[[Organization:American Society for Microbiology|American Society for Microbiology]] | volume=20 | issue=5 | year=2000 | issn=0270-7306 | doi=10.1128/mcb.20.5.1461-1477.2000 | pages=1461–1477| pmid=10669724 | pmc=85310 }}</ref>

====Size and gene content====
The ''C. elegans'' genome is about 100 million [[Biology:Base pair|base pair]]s long and consists of six pairs of chromosomes in hermaphrodites or five pairs of autosomes with XO chromosome in male ''C. elegans'' and a mitochondrial genome. Its [[Biology:Gene density|gene density]] is about one gene per five kilo-base pairs. [[Biology:Intron|Intron]]s make up 26% and [[Biology:Intergenic region|intergenic region]]s 47% of the genome. Many genes are arranged in clusters and how many of these are [[Biology:Operon|operon]]s is unclear.<ref>{{cite journal | vauthors = Blumenthal T, Evans D, Link CD, Guffanti A, Lawson D, Thierry-Mieg J, Thierry-Mieg D, Chiu WL, Duke K, Kiraly M, Kim SK | title = A global analysis of ''Caenorhabditis elegans'' operons | journal = Nature | volume = 417 | issue = 6891 | pages = 851–4 | date = June 2002 | pmid = 12075352 | doi = 10.1038/nature00831 | bibcode = 2002Natur.417..851B | s2cid = 4351788 }}</ref> ''C. elegans'' and other nematodes are among the few eukaryotes currently known to have operons; these include trypanosomes, [[Biology:Flatworm|flatworm]]s (notably the trematode ''[[Biology:Schistosoma mansoni|Schistosoma mansoni]]''), and a primitive [[Biology:Chordate|chordate]] [[Biology:Tunicate|tunicate]] ''[[Biology:Oikopleura dioica|Oikopleura dioica]]''. Many more organisms are likely to be shown to have these operons.<ref>{{cite journal | vauthors = Blumenthal T | title = Operons in eukaryotes | journal = Briefings in Functional Genomics & Proteomics | volume = 3 | issue = 3 | pages = 199–211 | date = November 2004 | pmid = 15642184 | doi = 10.1093/bfgp/3.3.199 | doi-access = free }}</ref>

The genome contains an estimated 20,470 [[Biology:Protein|protein]]-coding [[Biology:Gene|gene]]s.<ref>{{cite web
 |date=10 August 2011
 |title=WS227 Release Letter
 |url=http://www.wormbase.org/wiki/index.php/WS227
 |publisher=[[Biology:WormBase|WormBase]]
 |access-date=2013-11-19
 |archive-url=https://archive.today/2013.11.28-221823/http://www.wormbase.org/wiki/index.php/WS227
 |archive-date=28 November 2013
 |url-status=dead
 }}</ref> About 35% of ''C. elegans'' genes have human [[Biology:Homology|homologs]]. Remarkably, human genes have been shown repeatedly to replace their ''C. elegans'' homologs when introduced into ''C. elegans''. Conversely, many ''C. elegans'' genes can function similarly to mammalian genes.<ref name="Introduction to C. Elegans" />

The number of known RNA genes in the genome has increased greatly due to the 2006 discovery of a new class called ''[[Biology:21U-RNA|21U-RNA]]'' genes,<ref>{{cite journal | vauthors = Ruby JG, Jan C, Player C, Axtell MJ, Lee W, Nusbaum C, Ge H, Bartel DP | title = Large-scale sequencing reveals 21U-RNAs and additional microRNAs and endogenous siRNAs in ''C. elegans'' | journal = Cell | volume = 127 | issue = 6 | pages = 1193–207 | date = December 2006 | pmid = 17174894 | doi = 10.1016/j.cell.2006.10.040 | doi-access = free }}</ref> and the genome is now believed to contain more than 16,000 RNA genes, up from as few as 1,300 in 2005.<ref>{{cite journal | vauthors = Stricklin SL, Griffiths-Jones S, Eddy SR | title = ''C. elegans'' noncoding RNA genes | journal = WormBook | pages = 1–7 | date = June 2005 | pmid = 18023116 | pmc = 4781554 | doi = 10.1895/wormbook.1.1.1 }}</ref>

Scientific curators continue to appraise the set of known genes; new gene models continue to be added and incorrect ones modified or removed.

The reference ''C. elegans'' genome sequence continues to change as new evidence reveals errors in the original sequencing. Most changes are minor, adding or removing only a few base pairs of DNA. For example, the WS202 release of WormBase (April 2009) added two base pairs to the genome sequence.<ref name="WS202">{{cite web
 |date=29 May 2009
 |title=WS202 Release Letter
 |url=http://www.wormbase.org/wiki/index.php/WS202
 |archive-url=https://archive.today/2013.12.01-022934/http://www.wormbase.org/wiki/index.php/WS202
 |url-status=dead
 |archive-date=December 1, 2013
 |publisher=[[Biology:WormBase|WormBase]]
 |access-date=2013-11-19
 }}</ref> Sometimes, more extensive changes are made as noted in the WS197 release of December 2008, which added a region of over 4,300 bp to the sequence.<ref name="WS197">{{cite web
 |date=27 November 2008
 |title=WS197 Release Letter
 |url=http://www.wormbase.org/wiki/index.php/WS197
 |publisher=[[Biology:WormBase|WormBase]]
 |access-date=2013-11-19
 |archive-url=https://web.archive.org/web/20191017232138/https://wiki.wormbase.org/index.php/WS197
 |archive-date=17 October 2019
 |url-status=dead
 }}</ref><ref name="GenomeChanges">{{cite web
 |date=15 June 2011
 |title=Genome sequence changes
 |url=http://www.wormbase.org/wiki/index.php/Genome_sequence_changes
 |access-date=2011-08-13
 |publisher=[[Biology:WormBase|WormBase]]
 |archive-url=https://web.archive.org/web/20191017232140/https://wiki.wormbase.org/index.php/Genome_sequence_changes
 |archive-date=17 October 2019
 |url-status=dead
 }}</ref>

The ''C. elegans'' Genome Project's Wilson et al. 1994 found CelVav<ref name="Bustelo-2000" /> and a von Willebrand factor A domain<ref name="Sadler-1998" /> and with Wilson et al. 1998 provides the first credible evidence for an [[Biology:Aryl hydrocarbon receptor|aryl hydrocarbon receptor]] (AHR) homolog outside of vertebrates.<ref name="Hahn-2002" /> 2

====Related genomes====
In 2003, the genome sequence of the related nematode ''C. briggsae'' was also determined, allowing researchers to study the [[Biology:Comparative genomics|comparative genomics]] of these two organisms.<ref>{{cite journal | vauthors = Stein LD, Bao Z, Blasiar D, Blumenthal T, Brent MR, Chen N, Chinwalla A, Clarke L, Clee C, Coghlan A, Coulson A, D'Eustachio P, Fitch DH, Fulton LA, Fulton RE, Griffiths-Jones S, Harris TW, Hillier LW, Kamath R, Kuwabara PE, Mardis ER, Marra MA, Miner TL, Minx P, Mullikin JC, Plumb RW, Rogers J, Schein JE, Sohrmann M, Spieth J, Stajich JE, Wei C, Willey D, Wilson RK, Durbin R, Waterston RH | title = The genome sequence of ''Caenorhabditis briggsae'': a platform for comparative genomics | journal = PLOS Biology | volume = 1 | issue = 2 | pages = E45 | date = November 2003 | pmid = 14624247 | pmc = 261899 | doi = 10.1371/journal.pbio.0000045 | doi-access = free }}</ref> The genome sequences of more nematodes from the same [[Biology:Genus|genus]] e.g., ''C. remanei'',<ref>{{cite web |url=http://genome.wustl.edu/genome.cgi?GENOME=Caenorhabditis%20remanei |author=Genome Sequencing Center |title=''Caenorhabditis remanei'': Background |access-date=2008-07-11 |publisher=[[Organization:Washington University School of Medicine|Washington University School of Medicine]] |archive-url=https://web.archive.org/web/20080616091639/http://genome.wustl.edu/genome.cgi?GENOME=Caenorhabditis+remanei  |archive-date=2008-06-16}}</ref> ''C. japonica''<ref>{{cite web |url=http://genome.wustl.edu/genome.cgi?GENOME=Caenorhabditis%20japonica |author=Genome Sequencing Center |title=''Caenorhabditis japonica'': Background |access-date=2008-07-11 |publisher=[[Organization:Washington University School of Medicine|Washington University School of Medicine]] |archive-url=https://web.archive.org/web/20080626053444/http://genome.wustl.edu/genome.cgi?GENOME=Caenorhabditis+japonica  |archive-date=2008-06-26}}</ref> and ''C. brenneri'' (named after Brenner), have also been studied using the [[Biology:Shotgun sequencing|shotgun sequencing]] technique.<ref>{{cite journal | vauthors = Staden R | title = A strategy of DNA sequencing employing computer programs | journal = Nucleic Acids Research | volume = 6 | issue = 7 | pages = 2601–10 | date = June 1979 | pmid = 461197 | pmc = 327874 | doi = 10.1093/nar/6.7.2601 }}</ref> These sequences have now been completed.<ref>{{cite web|url=http://genome.ucsc.edu |title=UCSC genome browser |access-date=8 July 2014}}</ref><ref>{{cite journal | vauthors = Kuhn RM, Karolchik D, Zweig AS, Wang T, Smith KE, Rosenbloom KR, Rhead B, Raney BJ, Pohl A, Pheasant M, Meyer L, Hsu F, Hinrichs AS, Harte RA, Giardine B, Fujita P, Diekhans M, Dreszer T, Clawson H, Barber GP, Haussler D, Kent WJ | title = The UCSC Genome Browser Database: update 2009 | journal = Nucleic Acids Research | volume = 37 | issue = Database issue | pages = D755–61 | date = January 2009 | pmid = 18996895 | pmc = 2686463 | doi = 10.1093/nar/gkn875 }}</ref>

=== Other genetic studies ===
[[File:C. elegans.jpg|right|thumb|''C. elegans'' adult with GFP coding sequence inserted into a histone-encoding gene by ''Cas9''-triggered homologous recombination]]
As of 2014, ''C. elegans'' is the most basal species in the 'Elegans' group (10 species) of the 'Elegans' supergroup (17 species) in phylogenetic studies. It forms a branch of its own distinct to any other species of the group.<ref name="FélixPLoSOne2014">{{cite journal | vauthors = Félix MA, Braendle C, Cutter AD | title = A streamlined system for species diagnosis in Caenorhabditis (Nematoda: Rhabditidae) with name designations for 15 distinct biological species | journal = PLOS ONE | volume = 9 | issue = 4 | pages = e94723 | year = 2014 | pmid = 24727800 | pmc = 3984244 | doi = 10.1371/journal.pone.0094723 | bibcode = 2014PLoSO...994723F | doi-access = free }}</ref>

[[Biology:Tc1 transposon|Tc1 transposon]] is a DNA transposon active in ''C. elegans''.

== Scientific community ==
In 2002, the Nobel Prize in Physiology or Medicine was awarded to [[Biography:Sydney Brenner|Sydney Brenner]], [[Biography:H. Robert Horvitz|H. Robert Horvitz]], and [[Biography:John Sulston|John Sulston]] for their work on the genetics of organ development and [[Biology:Apoptosis|programmed cell death]] in ''C. elegans''. The 2006 Nobel Prize in Physiology or Medicine was awarded to [[Biography:Andrew Fire|Andrew Fire]] and Craig C. Mello for their discovery of [[Biology:RNA interference|RNA interference]] in ''C. elegans''.<ref>
{{cite journal | vauthors = Fire A, Xu S, Montgomery MK, Kostas SA, Driver SE, Mello CC | title = Potent and specific genetic interference by double-stranded RNA in Caenorhabditis elegans | journal = Nature | volume = 391 | issue = 6669 | pages = 806–11 | date = February 1998 | pmid = 9486653 | doi = 10.1038/35888 | bibcode = 1998Natur.391..806F | s2cid = 4355692 }}</ref> In 2008, [[Biography:Martin Chalfie|Martin Chalfie]] shared a Nobel Prize in Chemistry for his work on [[Biology:Green fluorescent protein|green fluorescent protein]]; some of the research involved the use of ''C. elegans''.

Many scientists who research ''C. elegans ''closely connect to Sydney Brenner, with whom almost all research in this field began in the 1970s; they have worked as either a postdoctoral or a postgraduate researcher in Brenner's lab or in the lab of someone who previously worked with Brenner. Most who worked in his lab later established their own worm research labs, thereby creating a fairly well-documented "lineage" of ''C. elegans'' scientists, which was recorded into the [[Biology:WormBase|WormBase]] database in some detail at the 2003 International Worm Meeting.<ref name="Harris">{{cite journal | vauthors = Harris TW, Antoshechkin I, Bieri T, Blasiar D, Chan J, Chen WJ, De La Cruz N, Davis P, Duesbury M, Fang R, Fernandes J, Han M, Kishore R, Lee R, Müller HM, Nakamura C, Ozersky P, Petcherski A, Rangarajan A, Rogers A, Schindelman G, Schwarz EM, Tuli MA, Van Auken K, Wang D, Wang X, Williams G, Yook K, Durbin R, Stein LD, Spieth J, Sternberg PW | display-authors = 6 | title = WormBase: a comprehensive resource for nematode research | journal = Nucleic Acids Research | volume = 38 | issue = Database issue | pages = D463-7 | date = January 2010 | pmid = 19910365 | pmc = 2808986 | doi = 10.1093/nar/gkp952 }}</ref>

== See also ==
* Animal testing on invertebrates
* [[Physics:Bioluminescence|Bioluminescence]]
* Eileen Southgate
* [[Biology:Intronerator|Intronerator]]
* [[OpenWorm]]
*[[Biology:WormBook|WormBook]]

{{clear}}

== References ==
{{Reflist|32em}}

== Further reading ==
{{Refbegin}}
* {{cite book | vauthors = Bird J, Bird AC | title = The structure of nematodes | publisher = [[Company:Academic Press|Academic Press]] | year = 1991 | isbn = 978-0-12-099651-3 | pages = 1, 69–70, 152–153, 165, 224–225 }}
* {{cite book |last1=Hope |first1=IA |title=''C. elegans'': a practical approach |publisher=[[Organization:Oxford University Press|Oxford University Press]] |year=1999 |pages=1–6 |isbn=978-0-19-963738-6}}
* {{cite book | vauthors = Riddle DL, Blumenthal T, Meyer RJ, Priess JR |year=1997 |url=https://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=ce2 |title=''C. elegans'' II |publisher=[[Organization:Cold Spring Harbor Laboratory Press|Cold Spring Harbor Laboratory Press]] |pages=1–4, 679–683 |pmid=21413221 |isbn=978-0-87969-532-3}}
{{Refend}}

== External links ==
{{Commons and category}}
* Brenner S (2002) Nature's Gift to Science. In. http://nobelprize.org/nobel_prizes/medicine/laureates/2002/brenner-lecture.pdf (also Horvitz and Sulston lectures)
* [https://web.archive.org/web/20170420234209/http://www.wormbase.org/ WormBase] – an extensive online database covering the biology and genomics of ''C. elegans'' and other nematodes
* [http://www.wormatlas.org WormAtlas] – online database on all aspects of ''C. elegans'' anatomy with detailed explanations and high-quality images
* [http://www.wormbook.org WormBook] – online review of ''C. elegans'' biology
* [https://www.ncbi.nlm.nih.gov/IEB/Research/Acembly/index.html?worm AceView WormGenes] – another genome database for ''C. elegans'', maintained at the NCBI
* [https://www.ncbi.nlm.nih.gov/books/bv.fcgi?call=bv.View..ShowTOC&rid=ce2.TOC ''C. elegans'' II] – a free online textbook.
* [http://www.wormweb.org/neuralnet WormWeb Neural Network] – an online tool for visualizing and navigating the connectome of ''C. elegans''
* [http://labs.bio.unc.edu/Goldstein/movies.html ''C. elegans'' movies] – a visual introduction to ''C. elegans''
* {{UCSC genomes|ce11}}
* [https://gd.eppo.int/taxon/CAEOEL ''Caenorhabditis elegans'' at eppo.int] (EPPO code CAEOEL)
*{{ Cite journal  |  title=Using C. elegans to study anesthesia | year=2022| doi=10.6084/m9.figshare.20963590.v1| url=https://visualiseyourthesis.figshare.com/articles/presentation/Neural_Correlates_of_Behavioural_Changes_During_Propofol_General_Anaesthesia_in_Caenorhabditis_Elegans/20963590| last1=Cylinder| first1=Drew}}

{{Model Organisms}}
{{Taxonbar|from=Q91703}}

[[Category:Animal models]]

{{Sourceattribution|Caenorhabditis elegans}}