Caenorhabditis elegans

09/28/2008

Secernentea

  Rhabditia

    Rhabditida

      Rhabditoidea

        Rhabditidae

        Caenorhabditis elegans (Maupas, 1900) Dougherty, 1955

Caenorhabditis elegans was initially described and named Rhabditis elegans by Maupas (1900) who collected it from rich humus soil in Algeria (north Africa) (Fatt, 1961); it was subsequently placed in the subgenus Caenorhabditis by Osche (1952) and then raised to generic status by Dougherty (1955).

The name is a blend of Greek and Latin (Caeno, recent; rhabditis, rod-like; elegans, elegant).

C. elegans as a Model System:

Much of the recognition for the selection and development of C. elegans as a model system in genetics and developmental biology can be attributed to Ellsworth C. Dougherty.  In 1964, while working in the Department of Nutritional Sciences at UC Berkeley and interested in axenic culture of nematodes, Dougherty introduced the idea of using C. elegans to Sydney Brenner and provided him with a culture of the nematode.

Two strains of C. elegans have historical importance. One strain, Bergerac, was collected in 1955 from the garden soil near Bergerac, France, by Victor Nigon of the Universite de Lyon (Nigon 1949; Fatt, 1961), and the other strain, Bristol, was isolated by L.N. Staniland (National Agricultural Advisory Service, London) from mushroom compost near Bristol, England (Nicholas et al. 1959).

Study of development and reproduction of C. elegans was possible because the strains were morphologically identical but physiologically different (Fatt, 1961). The Bergerac strain of C. elegans could not be cultured at temperatures above 18C; at that temperature it became infertile.  The Bristol strain can be cultured at temperatures up to 25C, though males will not copulate below 20C (Fatt and Dougherty, 1963; Nicholas, 1975). In several reported cases, rhabditid nematodes seem to be adversely affected by higher temperatures.  For example, embryogenesis fails at temperatures of 25C and higher in Rhabditis cucumeris isolated from soil in the Central Valley of California (Venette and Ferris, 1997).

Figure from Ankeny, 2001

Developmental Biology

Aging

Molecular Biology

Medicine-Drugs

Human Disease Model

Behavior:

    Chemotaxis

Reproductive Strategies:

• In some members of the family Rhabditidae a sequential hermaphroditism occurs. The gonad first produces sperms which are stored in a spermatheca. The gonad then produces oocytes which become fertilized eggs as they pass through the spermatheca.
• The process has been studied in most detail in Caenorhabditis elegans. In that species, about 150 sperm are produced in each arm of the gonad and stored in each spermatheca. The number of sperm produced apparently limits the number of offspring produced by the nematode to around 300 (Gems and Riddle, 1996).
• True males also occur in a population , but are rare (around 1:1000). When a hermaphroditic female is mated with several males, as many as1400 progeny may be produced (Kimble and Ward, 1988).

Sydney Brenner obtained his culture of the Bristol strain of C. elegans from Dougherty (Brenner, 1974). Virtually all C. elegans genetics has been done with the Bristol strain, more specifically with the N2 line that Sydney Brenner derived from the Bristol culture he obtained from Ellsworth Dougherty. 

Interestingly, until the mid 1970s, people working in developmental biology frequently confused C. briggsae and C. elegans and many of the cultures being used were mis-identified.  In the mid 1970s, graduate student Paul Friedman working with Ed Platzer at UC Riverside developed diagnostic biochemical criteria for separating the two species and resolved the confusion (Friedman et al, 1977).  

Morphology and Anatomy:

• Self-fertilizing hermaphrodites predominate in a population.
• Stoma long and tubular, cuticle lined, constricted inward at the posterior end in three bulges, each with two widely-spaced teeth.
• Hermaphrodite tail elongate, conical, with paired postanal phasmids.
• Hermaphrodite is digonic with vulva at about 51% of body length.  Length 1250-1400 µm. width 70-90 µm.
• Male slender with bursa supported by three groups of three rays on each side; paired spicules are not fused at tips. Length 825-890 µm. width 45-50 µm.

Sources: Fatt (1961), Nigon, 1949.

References

Andrássy, I. 1983. A taxonomic review of the suborder Rhabditina (Nematoda: Secernentia). ORSTOM, Paris.

Ankeney, R.A. 2001. The natural history of C. elegans research. Nature Reviews Genetics 2: 474-478.
Brenner, S. 1974.  The genetics of Caenorhabditis elegans. Genetics 77:71-94.

Brown, A. 2003. In the Beginning Was the Worm.  Simon & Schuster, London. 244p.
Dougherty, E.C. 1960. Cultivation of aschelminthes, especially rhabditid nematodes. Pp 297-318 in Sasser and Jenkins (eds) Nematology: fundamentals and recent advances.  UNC Press, Chapel Hill.

Dougherty, E.C. and H.G. Calhoun. 1948. Possible significance of free-living nematodes in genetic research. Nature 161:29.

Dougherty, E.C. and V. Nigon. 1949. A new species of the free-living nematode genus Rhabditis of interest in comparative physiology and genetics. J. Parasitol. 35: 11.
Dougherty, E.C.,  E.L. Hansen, W.L. Nicholas, J.A. Mollett, and E.A. Yarwood. 1959. Axenic cultivation of Caenorhabditis briggsae (Nematoda: Rhabditidae) with unsupplemented and supplemented chemically defined media. Ann. N.Y. Acad. Sci. 77: 176-217.

Fatt, H.V. 1961. Genetic control of maturation and reproduction in the nematode Caenorhabditis elegans. MA Thesis, University of California, Berkeley. 49p.

Fatt, H.V. and E.C. Dougherty. 1963. Genetic control of differential heat tolerance in two strains of the nematode, Caenorhabditis elegans. Science 141:266-267.

Friedman, P.A., E.G. Platzer, and J.E. Eby. 1977. Species differentiation in C. briggsae and C. elegans. J. Nematol. 9: 197-203.
Gems, D. and D. L. Riddle. 1996. Longevity of Caenorhabditis elegans reduced by mating but not gamete production. Nature 379:723-725.

Gochnauer, M.B. and E. McCoy. 1954. Responses of a soil nematode, R. briggsae, to antibiotics. J. Exp. Zool. 125:377-406.

Kimble, J. and S. Ward. 1988. Germ-line development and fertilization. In: W. B. Wood et al. The Nematode Caenorhabditis elegans. Cold Spring Harbor Laboratory Press.

Maupas, E. 1900. Modes et formes de reproduction des Nématodes. Arch, Zool. Exp, et Gén., (3e série), 8:463-624.

Nicholas, W.L., E.C. Dougherty, and E.L. Hansen. 1959. Axenic cultivation of C. briggsae (Nematoda: Rhabditidae) with chemically undefined supplements; comparative studies with related nematodes. Ann. N.Y. Acad. Sci. 77: 218-236.
Nigon, V. 1949. Les modalités de la reproduction et le déterminisme du sexe chez quelques nematodes libres. Ann. Sci. Nat. Zool. Biol. Anim. 11: 1-132.

Nigon, V. and E.C. Dougherty. 1949. Reproductive patterns and attempts at reciprocal crossing of Rhabditis elegans Maupas, 1900 and Rhabditis briggsae Dougherty and Nigon, 1949 (Nematoda: Rhabditidae). J. Exp Zool, 112:488-503.

Nigon, V. and E.C. Dougherty. 1950. A dwarf mutant of a nematode. A morphological mutant of Rhabditis briggsae, a free-living soil nematode. J. Heredity 41:103-109.
Riddle, D.L., T. Blumenthal, B.J. Meyer and J.R. Priess. 1997. C. elegans II. Cold Springs Harbor Press.

Venette, R. C. and H. Ferris. 1997. Thermal constraints to population growth of bacterial-feeding nematodes. Soil Biology and Biochemistry 29:63-74.

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