In this week's tutorial, the development of C. elegans will be examined. As you read the following text, you will come across a number of Web links. These links will provide information that outlines various aspects of worm development for which you will be responsible. There are also four movies to examine.
The nematode worm Caenorhabditis elegans has taken the world of developmental biology by storm over the past few years. The advantages for the study of development are legendary: transparent embryo and adult, ease of doing genetic analyses and a complete lineage map of every single cell in the body of the adult. It will also be the first multicellular organism to have its genome completely sequenced.
C. elegans is a free-living organism, which normally lives in the soil, where it feeds mainly on bacteria. In the laboratory, it is grown on agar plates or in liquid culture, with E. coli as the food source. These small (~1 mm long and 80 micrometers in diameter) worms have a life cycle lasting 3.5 days. If a single adult hermaphrodite is placed on a plate, up to 500,000 worms can be produced in just over a week (Hope, 1994). C. elegans has two sexes: a male and a self-fertilizing hermaphrodite.
We shall begin our study of C. elegans development by becoming acquainted with the worm itself. Notice that all organ systems are easily seen through the body wall. The worm is shown with the anterior end at the top. The body is comprised of a tube (the gut, comprised of a muscular pharynx and an intestine) within a tube (the cuticle, hypodermis, muscle and nerve cells). The space between them is the pseudocoelom, which contains the gonad. The image shown here is a hermaphrodite. The gonad of the hermaphrodite is bi-lobed; each lobe connects to a single mid-ventral vulva via an oviduct, spermatheca and a common uterus. The gonad of the male is single-lobed. It is located in a mid-ventral location. Sperm travel from the gonad, seminal vesicle and vas deferens, exiting through the cloaca.
We shall next study still micrographs and movies of early development. An overview of worm development has been prepared by Dr. Susan Strome. There are four movies to help in the visualization of the development of C. elegans, they can be accessed from the hard drive if you are in the Mac Lab.
For many years, C. elegans investigators were convinced that development was directed entirely by the parceling of morphogenic determinants during cleavage. However, we now know that embryonic induction plays a significant role in determination of cell fate. You should now examine the lineage map of founder cells. Return to the overview of worm development and trace the formation of the MS cell. Now do the same thing using the movie of early development (return to movie #4).
For more C.elegans movies, see the webpage maintained by Bob Goldstein's lab.
Hope, I. 1994. Caenorhabditis elegans, the nematode worm. In J. Bard (ed.), Embryos. Color Atlas of Development, Mosby-Year Book Europe, London, pp. 55-75.
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Leon Browder & Laurie Iten (Ed.) Dynamic Development
Last revised Wednesday, July 29, 1998