[
1987]
Since the last review in this series [Johnson, 1985], many papers have appeared dealing directly with the aging process in both Caenorhabditis elegans and Turbatrix aceti. We will review this work and also briefly review other areas of C. elegans research that may impact on the study of aging. C. elegans has become a major biological model; four "News" articles in Science [Lewin, 1984a,b; Marx, 1984a,b] and inclusion as one of three developmental genetics models in a recent text [Wilkins, 1986] indicate its importance. Recent work has verified earlier results and has advanced progress toward new goals, such as routine molecular cloning. The aging studies reviewed here, together with new findings from other areas of C. elegans research, lay the groundwork for rapid advances in our understanding of aging in nematodes. Several areas of research in C. elegans have been reviewed recently: the genetic approach to understanding the cell lineage [Sternberg and Horvitz, 1984] and a brief summary of cell lineage mutants [Hedgecock, 1985]. The specification of neuronal development and neural connectivity has been a continuing theme in C. elegans research and reviews of these areas have also appeared [Chalfie, 1984; White, 1985]. A major genetic advance is the development of reliable, if not routine, mosaic analysis [Herman, 1984; Herman and Kari, 1985], which is useful for the genetic analysis of tissue-limited gene expression. Hodgkin [1985] reviews studies on a series of mutants involved in the specification of sex. These include her mutations that cause XO worms (normally males) to develop as hermaphrodites and tra mutations that change XX hermaphrodites into phenotypic males. The work on the structure and development of nematode muscle has been summarized by Waterston and Francis [1985]. A comprehensive review of aging research, containing useful reference material on potential biomarkers, has appeared [Johnson and Simpson, 1985], as well as a review including
[
1990]
Caenorhabditis elegans is a short-lived species that has been widely used in the genetic dissection of development. This species is becoming important in the genetic analysis of aging because strains with mean life spans more than 70% longer than wild type have been identified both through the use of recombinant inbred lines and by the induction of single-gene mutants. Its unique hermaphroditic mode of reproduction leads to a lack of inbreeding depression and simplifies genetic analyses of quantitative traits such as length of life or behavior. Aging in this organism is composed of at least three independent processes: that specifying length of life, that specifying reproductive senescence, and that specifying senescence of the general motor system. These data suggest that aging is not a unitary process but that many different processes or independent components may be involved in various aspects of aging. Most importantly, an apparent single-gene mutation has been mapped to the middle of linkage group II; this mutation lengthens mean and maximum life span 60-110% and also decreases fertility about five-fold.