A genetic model organism: Caenorhabditis elegans are ~1 mm long hermaphroditic, free-living nematodes. Each individual produces oocytes and sperm and can internally self-fertilize, producing large isogenic populations. Males are produced at low rate by unbalanced meiosis. C. elegans combine the practical advantage of hermaphrodite reproduction (large number of genetically identical animals and ease of maintaining strains by self fertilisation) with the experimental advantages of classical sexual reproduction (to transfer mutations, outcross, map traits, …).
Short life-cycle and easy cultivation: In the laboratory, C. elegans is cultivated in agar dishes , and feed on E. coli bacteria. It can be easily housed and cultivated in large numbers (>10,000 worms/petri dish) or can be frozen in liquid nitrogen and recovered many years later. Each individual produce ~200 eggs, that reach reproductive maturity in ~4 days and last 2 to 3 weeks. This short life cycle and large progeny greatly facilitates biological study of development and ageing.
Mutants and transgenic: As human, the genome of C. elegans encode roughly 20.000 genes. ~80% of its genes have human homologues. Millions of mutants and transgenic strains are available to the community for analysis. Great for microscopy: C. elegans is transparent to light, turning it into a perfect organism to observe development or cell biology in-vivo, using contrast or fluorescent microscopy. Each individual contain a constant 959 somatic cells, including 302 neurons. The number and position of these cells during development and in the adult is constant.
A model for neuroscience: The compact nervous system of C. elegans consist of just 302 neurons, each has a reproducible location, functions and synaptic connectivity. The complex network made of ~7000 synapses and ~800 gap junctions is entirely described at the EM resolution. Neuronal differentiation and circuit assembly are well understood.
