Factors Affecting Lifespan In Freeliving S Ratti And C Elegans

The lifespan of the free-living adult female S. ratti is really very short; in fact it is the shortest-lived nematode reported. One possibility is that this very short lifespan is not the result of aging in the usual sense. For example, mortality might result from failure to feed, or a gross anatomical defect not seen in other nematodes. To address these issues, we compared aging in free-living S. ratti with that in C. elegans in two ways. First, we tested the effect of factors known to affect aging in C. elegans and in S. ratti free-living adults. Second, we asked whether the age-associated changes in C. elegans behavior, morphology and appearance are also seen in S. ratti. Overall, our findings strongly support the view that the short lifespan in S. ratti free-living adults is the result of typical nematode aging, but which is happening at an unusually swift pace.

In C. elegans, lifespan is reduced by various factors, including the E. coli food source (Gems and Riddle, 2000; Garigan et al., 2002), higher temperature (Klass, 1977), mating between the sexes (Gems and Riddle, 1996) and attempted mating between males (Gems and Riddle, 2000). In S. ratti, lifespan (Figure 20.3A) and lifetime fecundity (Figure 20.3B) were reduced by higher temperatures, as in C. elegans (Klass, 1977).

However, mating did not affect lifespan in S. ratti in the same way as it does in C. elegans. Thus, mating (manipulated by adjusting the male:female ratio from 0 to 4.0) had no effect on S. ratti free-living female lifespan,

Temperature (°C) Temperature (°C)

Figure 20.3. (A) Effects of temperature on mean (o, - - - -) and maximum (x, -) lifespan of virgin free-living females. S. ratti adults die within 24 hours at 37°C. (B) Effect of temperature on mean per capita lifetime fecundity of S. rattifemales, mated on day one only

(o, - - - -) or mated throughout life (x, -). (C) The mean (±1 SE) daily per capita fecundity of the parasitic females (•) and of the free-living females (■) (mean ±1 SE; adapted from Gardner et al., 2004) over time, which is shown on a log scale.

Figure 20.3. (A) Effects of temperature on mean (o, - - - -) and maximum (x, -) lifespan of virgin free-living females. S. ratti adults die within 24 hours at 37°C. (B) Effect of temperature on mean per capita lifetime fecundity of S. rattifemales, mated on day one only

(o, - - - -) or mated throughout life (x, -). (C) The mean (±1 SE) daily per capita fecundity of the parasitic females (•) and of the free-living females (■) (mean ±1 SE; adapted from Gardner et al., 2004) over time, which is shown on a log scale.

whereas in males it actually increased lifespan. Thus lifespan in S. ratti and C. elegans is affected in the same way by some factors (temperature, food source in data not shown, proliferating bacteria) but in different ways by others (mating).

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