C. elegans is one of the simplest multicellular organisms, and is the first to have its 100 Mbp genome entirely sequenced. The C. elegans life cycle is fairly short, three days, and the worm only lives two to three weeks. It develops through four larval stages, embryogenesis, gonadogenesis, spermatogenesis and oogenesis. Cells differentiate to form complex tissue and organ systems. A nervous system is developed with a 'brain' (a circumpharyngeal nerve ring), enabling rudimentary learning. It is transparent and each of the 959 somatic cells is visible through a microscope. Roughly 300 cells are neurons, consisting of sense organs in the head, mediating taste, smell, temperature and touch responses. There are 81 muscle cells aiding transport movement by four longitudinal bands of muscle. Dorsal-ventral waves generate through the body by relaxation and flexing of sub-dorsally and sub-ventrally paired muscles, and the animal is thrust through the soil.
There are two sexes among C. elegans: a self-fertilizing hermaphrodite and a male, though males are rarely found in populations. It reproduces sexually, producing sperm and eggs and the reproductive system is responsible for most of the volume of C. elegans. The worm has a digestive, excretory and neuromuscular system and is very easy to culture, leading to its application in many genetic and biological studies.
C. elegans as a model organism:
- short life cycle of 3 days
- self-fertilizing hermaphrodite - easy to produce homozygous mutant stocks
- shares biological characteristics central to biological problems
- handled easily (as a microorganism grown on agar plates)
- all somatic cells of its body are visible with a microscope
