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Chromadorea
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Rhabditia
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Rhabditida
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Rhabditoidea
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Rhabditidae
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- 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).
- Self-fertilizing protandrous 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).
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Distribution:
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
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).
Studies on C. elegans include areas of:
Developmental
Biology
Aging
Molecular Biology
Medicine-Drugs
Human Disease Model
Behavior:
Chemotaxis
Nobel prizes in 2002
and 2006 were awarded for
studies that used C. elegans as a model system.
Bacteria; laboratory cultures are usually maintained on Escherichia
coli OP50 (a gram negative rod-shaped bacterium) maintained on defined
media: NGM (= nematode growth medium):
- Agar 17.5 g/l
- Sodium Chloride 3.0 g/l
- Peptone 2.5 g/l
- Cholesterol 0.005 g/l (added after autoclaving and cooling
to 55C)
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). The
abundance of true males can be increased by culturing the nematodes at
higher temperatures (above 25C).
- When
a hermaphroditic female is mated with several males, as many as1400 progeny
may be produced (Kimble and Ward, 1988).
Eggs may hatch within the bodies of older females. The females then die
and the juveniles consume bacteria decomposing the female body. This has
been thought to occur when the vaginal muscles are no longer strong enough to
eject the eggs and is termed
endotokia matricida due
to the resultant death of the female. In the Caenorhabditis elegans
literature, the phenomenon has been termed "bagging" . The hypothesis has
been advanced that intra-uterine hatch is a part of the C. elegans
life cycle, and complements androdioecy ( the existence of a hermaphrodite
population and a male population) and the dauer (a resistant or enduring
stage) stage to enhance progeny survival and dispersal under stress.
Consequently, per the hypothesis, matricidal hatching, has been
perpetuated in C. elegans through evolutionary time as it confers a
survival advantage when resources are scarce or conditions unfavorable (Chen &
Caswell-Chen, 2003).
- 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.
Chen J.; Caswell-Chen E.P. 2003. Why Caenorhabditis elegans adults
sacrifice their bodies to progeny. Nematology 5:641-645.
- 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.
For more information on nematodes:
Nemaplex home page.
Copyright © 1999 by Howard Ferris.
Revised: November 30, 2012.