Worm Breeder's Gazette 14(1): 97 (October 1, 1995)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

What is the wild type life span of C. elegans?

David Gems and Don Riddle

Division of Biological Sciences, University of Missouri, Columbia, MO 65211

In order to characterize the determinants of life span in C. elegans  an
accurate estimate of wild type life span is required as a baseline.
However, estimates of the life span of N2 hermaphrodites under ostensibly
identical conditions (monoxenic plate culture, 20 C) is highly variable,
varying from 11.4 to 19.9 days (50% survival or mean life span)(1). Recent
reports have given estimates of N2 hermaphrodite mean life span (same
conditions) ranging from 11.8 days (2) to 20 days (3). In order to
establish whether this reflects strain differences or environmental
variation we measured the life spans of six N2  lines from different
locations under identical conditions. These were the male and
hermaphrodite stocks distributed by the CGC (here denoted CGCM an CGCH,
respectively); the Riddle lab male and hermaphrodite stocks which should
be identical to their CGC equivalents (denoted DRM and DRH); JW, an N2
strain obtained by Don Riddle from the LMB, Cambridge in the mid-1970s;
and BA, the Ward lab N2, which originated from the LMB in the mid-1970s.

 In two or more trails using 50-60 animals each we observed the following
strain variation in mean life span, measured from L4): CGCM,  17.3+0.3
(SEM) days; DRM, 17.4+0.6: CGCH, 16.0+0.3; DRH,  15.5+0.4 days; JW,
12.7+0.4 days; and BA, 14.0+0.7 days (see figure). Thus, CGC and DR male
strains are distinct from CGC and DR hermaphrodite  strains with respect
to hermaphrodite life span. A similar pattern of variation was seen in
male life spans, although the life spans of CGCM/DRM and CGCH/DRH males
were not distinguishable.

Which is the real wild type life span? Clearly , the established
convention that N2 is wild type by definition, cannot answer this
question. However, F1 progeny from crosses between JW and BA had a life
span (50% survival) of 14.5+0.6 days, compared to 11.7+0.8 and 12.0+0.3
days for JW and BA, respectively (two trials). This suggests that JW and
BA are mutant and that complementation is occurring in the F1 progeny
resulting in a longer life span relative to the parental strains.

This study underscores the importance of using the same strain of N2 as a
starting point in aging studies, and as the genetic background in
comparing mutations which affect life span.

(1) Johnson and Simpson, CRC Handbook on the Biology of Aging 481-495,
(2) Van Voorhies, Nature 360 456-458, 1992.
(3) Kenyon et al, Nature 366 461-464, 1993.