WormClassroom

C. elegans is a free-living, non-parasitic soil nematode that can be found throughout the world. It is transparent and about 1mm in size. “Worm” is its nickname. Researchers working with C. elegans call themselves “worm people” and form the “worm community” of research.

A Quick Peek at a Plate of C. elegans

• Look at the biggest worm, it is an adult worm.
• The one next to the biggest worm is a larva.
• 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.
• There is also a larger version of this movie.

Feed

C. elegans feeds on bacteria (such as E. coli) or anything else that fits in its mouth. Video of a worm eating.

Sexes

There are two sexes, hermaphrodite and male. 1 2

Hermaphrodite

Hermaphrodite (color diagram)

Male

Sex Determination

C. elegans has five pairs of autosomes and one pair of sex chromosome. 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.

Fertilization

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 progeny than the self-fertilization of a hermaphrodite (about 350 progeny). 3

Life Cycle & Life Span

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

C. elegans life cycle: Click for more information

• 1. Hermaphrodite and male diagrams: Wood, W. B. (Ed.). (1988). The nematode Caenorhabditis elegans. New York, NY: Cold Spring Harbor Laboratory Press.
• 2. Hermaphrodite colored image: WormAtlas
• 3. C. elegans nothanks drawing: Hernan Espinoza, 7/17/1999