It takes a long time for aging research by using a creature with a long life span. Nematode C. elegans, which is approximately 1 mm in length and lives its short life underground by eating bacteria, is a model organism convenient to experiment with. It has a basic system as an animal, including muscles, a digestive tube, neural system, and skin, and shows a variety of behaviors in spite of its simple neural system. At 20 degrees C, a nematode develops from a fertilized egg to the adult stage in three days. This is easy to observe due to its transparent body. The process of which cell divides into which cell and which cell dies （Note） is predetermined precisely, and the number of cells of adult nematodes is 1,031 for males and 959 for hermaphrodites.

 For several days after being an adult, a nematode actively moves around to eat and lay eggs, but from around 10 days after its birth, the movement gradually becomes slow. The transparent body gets brown granules, orderly muscles become disorderly, and dead cells get blisters. Unlike the process of becoming an adult, this aging process varies depending on individuals, organs, and cells. In their natural settings, aged nematodes die from around the 10th day, and the maximum length of life is about 25 days.

 By using this C. elegans, various research on the genetic factors of life span have been conducted. Bringing about mutations by agent and checking the average length of their lives, many mutants with several times the average and maximum length of life of the wild strain have been obtained. Under ordinary conditions, some mutants do not show much difference from the wild strain in terms of their activity and reproductive performance when they are at the young adult stage. By checking the mutated genes of these mutants, what kind of protein those genes make and where and how they work, the mutual relationship of gene groups that influence the length of life has become clearer.

 Concerning the molecules that have been identified in experiments using nematodes to make up the signal transduction mechanism to control the length of life, homologous ones exist in human beings. It was also confirmed that mutated homologues in mice extended their life expectancy. It is expected that the aging mechanism of human beings will be elucidated by promoting, in the future, research with nematodes on the mechanism to control aging, and to decide life expectancy, and by researching on commonality with higher animals including human beings.

 For the achievement of introducing C. elegans as a model organism, the Nobel Prize for Physiology and Medicine in 2002 was given to Dr. Sydney Brenner （present President, Okinawa Institute of Science and Technology）.

Note：
 The programmed cell death that is caused by a cell itself is called apotosis.