Life span of the wild and mutant nematode Caenorhabditis elegans. Effects of sex, sterilization, and temperature.

The survival of Caenorhabditis elegans was studied comparing animals of different sexes, sterilized animals, and animals grown at different temperatures as a prelude to more detailed cytological and genetic analysis of aged nematodes. Temperature-sensitive sterile mutants, animals sterilized by 5-fluorodeoxyuridine treatment, and wild-type males showed little difference in life span from that of wild-type hermaphrodites, although slight changes in P (time of beginning of the dying phase) or T1/2 (half-life of the population in the early dying phase) values were observed. At higher temperatures, P and T1/2 values markedly decreased, indicating a shortened life span. Temperature shift between 16 degrees C and 25 degrees C revealed that an increase in life span always involved low temperatures after the adult phase. High temperature treatment during the growing phase or after the adult phase caused an earlier start of the dying phase, but a downward temperature during the adult phase resulted in a great increase in the half-life of the population (T1/2). The results suggest that the life span of C. elegans is rigidly determined by somatic cells and markedly influenced by the effects of temperature on the cells during the post-mitotic state.