What is C. elegans?
A quick peek at a plate of C. elegans

(About 230 KB, movie length: 4 ")

About this movie:

  • Look at the biggest worm, it is an adult worm.
  • The one next to the biggest worm is a larvaG.
  • There is a scale in the right lower corner to let you understand the relative size of the worm.
  • You can also see this adult worm’s head which is toward upper right corner.
  • You may notice, C. elegans can move both forward and backward.
  • There is an embryo to the upper left corner.
  • For a larger version of this movie, click here.

A nematode

It is a free living, non-parasitic soil nematodeG that can be found throughout the world.


It feeds on bacteria (e.g. E. coli), or anything that fits into its mouth.

A worm eating


There are two sexes, hermaphroditeG and male. More about body shape of hermaphrodite and male can be found here.

(Click the image to see an enlarge image)
Up: Hermaphrodite, Down: Male. Notice the difference between their tail.


Hermaphrodites can self-fertilize or cross with males. However, hermaphrodites cannot fertilize another hermaphrodite. Males can only cross with hermaphrodites. Crossing between a male and hermaphrodite produces more progenyG than the self-fertilization of a hermaphrodite (about 350 progeny).

Sex Determination

C. elegans has five pairs of autosomesG and one pair of sex chromosomeG. Sexual determination in C. elegans is similar to Drosophila; the ratio of sex chromosomes to autosomes determines its sex. If the 6th chromosome pair is XX, then C. elegans will be a hermaphrodite. A XO combination in the 6th chromosome pair will produce a male. XO combination in male is the spontaneous loss of X chromosome (XX -> XO). When a male crosses with a hermaphrodite, the progeny will be half males and half hermaphrodites.

Life Cycle & Life Span

Its life cycle and life span are about 3 days and 3 weeks, respectively.

Life Cycle & Life Span
(Flash movie, size: 8 KB, movie length: 9")

Life Cycle


It is transparent and the adult worm is about 1mm in size.


"Worm" is its nickname. Researchers working with worm call themselves as "worm people" and form the "worm community" of research.


1. A Worm eating (Paul Muhlrad, 02/14/2001, The Ward Lab, Retrieved 12/13/04, from http://www.mcb.arizona.edu/wardlab/gallery.html)

2. Hermaphrodite and male: Wood, W. B. (Ed.). (1988). The nematode Caenorhabditis elegans. New York, NY: Cold Spring Harbor Laboratory Press.

3. Hermaphrodite colored image: WormAtlas, access 03/30/05

4. C. elegans nothanks drawing (Hernan Espinoza, 7/17/1999, web page no longer available)



Autosome: any chromosome other than sex chromosome. (Molecular Cell Biology/Harvey Lodish [et al.] – 4th)

Chromosome: in eukaryotes, the structural unit of the genetic material consisting of a single, linear double-stranded DNA molecule and associated proteins. During mitosis, chromosomes condense into compact structures visible in the light microscope. In prokaryotes, a single circular double-stranded DNA molecule constitutes the bulk of the genetic material. (Molecular Cell Biology/Harvey Lodish [et al.] – 4th)

Hermaphrodite: hermaphrodite is the form that can make both sperm and oocytes and can self-fertilize. C. elegans has both hermaphrodites and males. The male can mate with hermaphrodites to produce cross progeny.

Larva (Larvae): The immature forms of C. elegans. Aafter hatching, C. elegans undergo a series of larval stage, called L1 – L4, before becoming adults.

Nematode: nematodes, or roundworms, are generally slender worms, circular in cross section. They are remarkably uniform in structure but vary a lot in size and way of life. Some live as parasites in other animals; some are parasites of plants and some live free in soil, marine mud and decaying organic matter.

Progeny: offspring; the immediate descendants of an organism.