There are six chromosomes in C. elegans ?five pairs of autosomes (chromosomes I, II, III, IV, V) and the sex chromosome, X (this is the letter X, not the Roman numeral ten). Hermaphrodites have two X chromosomes (designated XX). Males have one X chromosome (designated XO); having only one chromosome instead of a pair is called the hemizygous state. This state can be produced by the loss of one X chromosome or by mating. Males cannot produce progeny on their own. However, they can cross-fertilize hermaphrodites. They are commonly used in C. elegans genetics for making genetic combinations.
One of the advantages of working with C. elegans is that it has a short life cycle. The life cycle is temperature-dependent. C. elegans goes through a reproductive life cycle (egg to egg-laying parent) in 5.5 days at 15℃, 3.5 days at 20℃, and 2.5 days at 25℃.
C. elegans eggs are fertilized within the adult hermaphrodite and laid a few hours afterward--at about the 40 cell stage. Eggs hatch and animals proceed through 4 larval stages, each of which ends in a molt. When animals reach adulthood, they produce about 300 progeny each. They live a total of about 2 weeks.
Note that C. elegans can adopt an alternative life form, called the dauer larval stage, if plates are too crowded or if food is scarce. Dauer larvae are thin and can move but their mouths are plugged and they cannot eat. Interestingly, dauers can remain viable for three months. They appear to be non-aging: dauer larvae can roam around for months and then reenter the L4 stage when they encounter a food source and live about 15 more days! Think about it--those worms can live nearly 10 times their normal lifespan!
C. elegans development.
C. elegans development is characterized better than any multicellular organism the complete cell lineage of the animal has been recorded. A cell lineage is a description of all the cell divisions that occur to generate a specific group of differentiated cells (in the case of C. elegans, the entire animal!). In other words, the developmental pattern of each somatic cell is known, from the zygote to the adult worm. Thus, a scientist can identify any cell at any point in development, and know the fate of that particular cell.