Editing Caenorhabditis elegans (section)

==Anatomy==
[[File:CrawlingCelegans.gif|thumb|300px|right|Movement of wild-type]]
''C.{{nbsp}}elegans'' is [[segmentation (biology)|unsegmented]], [[wikt:vermiform|vermiform]], and [[symmetry (biology)#Bilateral symmetry|bilaterally symmetrical]]. It has a [[cuticle]] (a strong outer covering, as an [[exoskeleton]]), four main [[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.{{nbsp}}elegans'' includes a mouth, [[pharynx]], [[intestine]], [[gonad]], and [[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.{{nbsp}}elegans'']]
[[File:C_elegans_cell_and_nucleus_sizes.svg|thumb|300px|right|  Size and morphology of different ''C.{{nbsp}}elegans'' cells]]

In relation to lipid metabolism, ''C.{{nbsp}}elegans'' does not have any specialized adipose tissues, a [[pancreas]], a [[liver]], or even blood to deliver nutrients compared to mammals. Neutral lipids are instead stored in the intestine, epidermis, and embryos. The [[epidermis]] corresponds to the mammalian adipocytes by being the main [[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.{{nbsp}}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 [[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 [[spicule (nematode)|spicules]]. Hermaphrodites have two [[ovaries]], [[oviducts]], and [[spermatheca]], and a single [[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.{{nbsp}}elegans,'' approximately one-third of all the somatic cells in the whole body.<ref name="pmid28889277">{{cite book | vauthors=Soares FA, Fagundez DA, Avila DS | chapter=Neurodegeneration Induced by Metals in Caenorhabditis elegans | series=Advances in Neurobiology | title=Neurotoxicity of Metals | 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> Many neurons contain dendrites which extend from the cell to receive neurotransmitters or other signals, and a [[Process (anatomy)|process]] that extends to the nerve ring (the "brain") for a synaptic connection with other 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.{{nbsp}}elegans'' has excitatory [[cholinergic]] and inhibitory [[GABAergic]] motor neurons which connect with body wall muscles to regulate movement. In addition, these neurons and other neurons such as interneurons use a variety of neurotransmitters to control behaviors.<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 (cropped).jpg|thumb|''C. elegans'' under a microscope]]
Numerous gut granules are present in the intestine of ''C.{{nbsp}}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 [[endocytosis]], but they are considerably larger, reinforcing the view of their being storage organelles.
A particular feature of the granules is that when they are observed under [[ultraviolet light]], they react by emitting an intense blue [[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 [[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 as a possible link to the [[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>