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Caenorhabditis elegans
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Caenorhabditis elegans

C. elegans
Scientific classification

Caenorhabditis elegans (C. elegans) is a free-living nematode (a roundworm), about 1 mm in length, which lives in a temperate soil environment. Research into the molecular and developmental biology of C. elegans began in 1965 by Sydney Brenner.

C. elegans is vermiform, bilateral in symmetry, with a cuticle integument, no segmentations, with four main epidermal cords and a fluid filled pseudocoelomate cavity. Members of the species also have an organ system and a closed circulatory system. They feed on microorganisms such as Escherichia coli bacteria. C. elegans has a male and hermaphrodite sex. The basic anatomy of C. elegans includues a mouth, pharynx, intestine, gonad, and collagenous cuticle. Males have a single-lobbed gonad, vas deferens, and a tail specialized for mating. Hermaphrodites have two ovaries, oviducts, spermatheca, and a single uterus.

A basic description of the organisms’ life cycle is that C. elegans eggs are laid by the hermaphrodite. After hatching, they pass through four larval stages (L1-L4). When crowded or in the absence of food, C. elegans can enter an alternative third larval stage called dauer. Dauers are stress-resistant and do not age. Hermaphrodites produce sperm during the L4 stage, and lay eggs as adults. The male can inseminate the hermaphrodite, which will use male sperm preferentially. The average life span of the laboratory strain of C. elegans at 20 °C is about 2-3 weeks, and the generation time is only a few days.

C. elegans is used as a model organism. Specimens are cheap and easy to maintain in the laboratory. C. elegans has been especially useful for studying cellular differentiation, and was the first animal to have its genome completely sequenced. The C. elegans genome contains more than 19,000 genes and approximately 100 million base pairs. This organism is the subject of a proposal which involves cataloguing its glycome.

From a research perspective, C. elegans has the advantage of being a multicellular eukaryotic organism which is simple enough to be studied in great detail. The developmental fate of all of its 959 somatic cells has been mapped out. (There are originally 1090 cells but 131 are eliminated by apoptosis.) In addition, C. elegans is one of the simplest organisms with a nervous system. Research has explored the neural mechanisms responsible for two of C. elegans' more interesting behaviors: chemotaxis and thermotaxis. In addition, recent research at the University of Toronto has shown that the worm appears to be capable of a simple form of associative learning, with recall being dependent on the environmental context.

In 2002, the Nobel Prize for Medicine was awarded to Sydney Brenner, H. Robert Horvitz and John E. Sulston for their work on the genetics of development and programmed cell death in C. elegans. C. elegans made news when it was discovered that specimens had survived the Space Shuttle Columbia's disintegration in February, 2003.

Loss of function mutations in daf-2, the C. elegans insulin receptor gene, have been shown to double the lifespan of the worm. This gene is involved in regulating resistance to oxidative stress.


  1. Riddle, D.L., Blumenthal, T Meyer, R. J., and Priess, J.R., 1997. C Elegans II. Cold Spring Harbor Laboratory Press, New York, pp1-4, 679-683.
  2. Hope, I.A. 1999. C. elegans A practical approach. Oxford University Press, New York, pp1-6.
  3. Bird, A.F, and Bird, J. 1991. The Structure of Nematodes. Academic Press, Inc. San Diego, pp 1, 69-70, 152-153, 165, 224-225.
  4. Avery, Leon. September 19, 2003. Caenorhabditis elegans WWW Server
  5. T. C. Ferree, B. A. Marcotte and S. R. Lockery (1997), "Neural network models of chemotaxis in the nematode C. elegans", Advances in Neural Information Processing Systems 9:55-61. MIT Press. [1]

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