as a tractable, long-lived model system for senescence.

represents a unique model system for the study of senescence, with the opportunity for the comparison of non-aging and induced senescence. maintains three stem cell lineages, used for continuous tissue morphogenesis and replacement. Recent work has elucidated the roles of the insulin/IGF-1 signaling target FoxO, of Myc proteins, and of PIWI proteins in stem cells. Under laboratory culture conditions, show no signs of aging even under long-term study. In contrast, can be experimentally induced to undergo reproduction-associated senescence. This provides a powerful comparative system for future studies.