WormClassroom

This movie shows a wild type C. elegans embryogenesis (from an embryo to a worm). Please observe this movie and come up with your observations and questions for discussion. Some background information on cell structures will help you observe this movie.

Questions to Get You Thinking:

• Are the two daughter cells same or different sizes?
• Does the embryo grow while its cell number increases?
• Are daughter cells always the same size or can they be different sizes?
• Does cell number increase in the rate of 2 X (1 -> 2 -> 4 -> 8 -> 16 —)?
• Why do cells divide at different time?
• Why are the daughter cells different sizes?
• How do cells know where to divide or to go?
• Do all the cells divide?
• Does the embryo grow while its cell number increases?
• Does the size (e.g.: volume) of a mother cell equal to the sum of its two daughter cells? (You might want to use measurement tools, such as ImageJ, for comparison.)

Dimensions of this embryo: 55 (µm in width) X 30 (µm in height), Magnification: 1000X

It takes approximately 14 hours for a C. elegans zygote to hatch. As you might notice in this movie, the recording time for the embryo development was only up to around 10 hours. A few hours were skipped to simplify the presentation.

Tools and Helpful Information

You might find tools such as ImageJ helpful in characterizing the embryo’s development in terms of changes in cell size and cell number etc.

ImageJ is a cross-platform on-line tool. It can be used to measure the size of the embryo. See examples and documentation.

Some information from WormBase might help you characterize C. elegans embryogenesis too. Information such as when a cell appears can be found in the “Individual Cell Report” in Wormbase. See Using WormBase to Find Cell Pedigree for more information.

As you navigate the cell pedigree, you might expect that two daughter cells from the same mother cell should appear at the same time. However, this is not necessarily the case. For example, in WormBase “C” appears at 67′ and “P3” appears at 76′. Please keep in mind that the temporal information provided is an approximate time that a cell appears.

Movie Credits

Crawling worm at the end thanks to the Bob Goldstein lab, 08/24/03, http://labs.bio.unc.edu/Goldstein/crawl.mov)