What is C. elegans ?

An adult hermaphrodite C. elegans worm
Image © Wikipedia

The roundworms and threadworms, a phylum of smooth-skinned, unsegmented worms with a long cylindrical body shape tapered at the ends; includes free-living and parasitic forms both aquatic and terrestrial. (Academic Press Dictionary of Science and Technology). C. elegans is a non-hazardous, non-infectious, non-pathogenic, non-parasitic organism. It is small, growing to about 1 mm in length, and lives in the soil—especially rotting vegetation—in many parts of the world, where it survives by feeding on microbes such as bacteria. It is of no economic importance to man.

C. elegans neurons share many features with human neurons. Like human neurons, C. elegans neurons are composed of a cell body that contains the cell nucleus and the majority of the cellular organelles; dendrites, which are highly branched and receive signals from other neurons or sensory structures; axons, which transmit signals to other neurons or effector cells; and an axon hillock, the point at which the cell body and axon meet that serves as the point for generation of action potentials. One major difference between C. elegans neurons and human neurons is that C. elegans neurons are never wrapped in myelin. While many of the neurons in humans, particularly in the brain, are not wrapped in myelin, most of the neurons in the human peripheral nervous system are myelinated to preserve action potential intensity over long distances and to speed up signal transmission by serving as an insulator. C. elegans neurons do not transmit signals across large distances, since C. elegans grow to be only about 1 mm long, and thus do not have a need for myelin. The neuronal system is the most complex organ system in the C. elegans, making up just under one third (302 of 959) of the cells of an adult hermaphrodite. The C. elegans neuronal system is made of two independent nervous systems; the pharyngeal and the somatic nervous systems. The pharynx is a tube-like muscle pump that concentrates food, grinds it, and transports it to the intestine. The pharyngeal nervous system is made up of 20 neurons responsible for the coordination of pharyngeal (feeding) activities and interacts with the somatic nervous system through just two interneurons. The remaining 282 neurons in C. elegans make up the more complex somatic nervous system that is in charge of coordinating all other c. elegans function.