Worm Breeder's Gazette 7(1): 65

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Effects of Deveolpmental Blocks on Lifespan

S. Kline, T.E. Johnson

Figure 1

Klass and Hirsh (1976) observed that the time a nematode spends in 
the dauer larval stage prolongs lifespan proportionately.  Our studies 
were designed to determine if blocking development in other larval 
stages also results in an extension of life proportional to the length 
of time spent in the blocked state.  We have tried two ways of 
blocking development: use of accumulator mutants (to block development 
at various larval stages), or starvation.
A battery of temperature-sensitive accumulator mutants was picked 
from the Hirsh collection and screened for stage of block, tightness 
of block, and reversibility of the block upon return to permissive 
conditions.  Developmental stage was monitored by measuring the length 
of heat-killed worms with an ocular micrometer.  Although many tight 
mutants were found in the Hirsh collection, none appeared to be 
readily reversible.  We therefore turned to starvation blocks.
Larvae can survive long periods of starvation with relatively little 
mortality.  The mean lifespan of L1 larvae starved at the time of 
hatch by suspension in S Basal with no cholesterol or food is 11 days 
at 20 C.  Upon return to growth conditions the larvae resume normal 
growth and development.  We have found that the time spent under 
starvation conditions is added to the total lifespan of the worm (see 
Table 1).  The mean lifespans suggest a correspondence between a day 
of starvation and a day of extra life.  The standard survival 
statistic (Gehan) was incremented by steps of one day in estimating 
the best fit.
[See Figure 1]
We are continuing this study by looking at other ways of blocking 
development, as well as by extending starvation blocks to other larval 
stages.  One problem we have encountered is that starvation after 48 
hours blocks further size increase but not development.  This results 
in mature but small adults which are killed by the hatching of unlaid 
eggs within the body of the mother.

Figure 1