Worm Breeder's Gazette 1(1): 9

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.

The Efficiency of Sperm Utilization in the Hermaphrodite

S. Ward, J.S. Carrel

Figure 1

Since observing that two of Jim Lewis's alleles of chemotaxis 
defective gene 1 (che 2) were sterile at 25  due to sperm dysfunction, 
much of the effort in our laboratory has been to determine the reason 
for this sterility.  In order to do this, it has been necessary to 
study normal spermatogenesis and fertilization.  One question that we 
have asked is what fraction of sperm in a wild-type hermaphrodite 
normally fertilize eggs?
The experiment to answer this question was simply to follow a 
synchronized population of wild-type hermaphrodites determining the 
number of sperm remaining in each animal by using the Feulgen stain 
and determining the number of zygotes produced by counting progeny and 
fertilized eggs.  Several time points were taken to be sure that sperm 
were indeed only synthesized during L4 and early adult as observed by 
Hirsh, Oppenheim, and Klass (1976) and others.  The results of this 
experiment are summarized in the table below.
[See Figure 1]
The population was initiated by collecting animals hatched during a 
one-hour period.  The sperm per worm was determined in Feulgen stained 
whole mounts by counting the small, densely staining, hollow looking 
nuclei characteristic of stained sperm.  The sperm decrease is 
decrease in sperm from the maximum number.  Zygotes per worm is the 
sum of progeny laid plus fertile eggs in the worms when fixed.  
Zygotes/sperm measures the efficiency of sperm utilization; the error 
shown is twice the standard error of the mean propagated from the 
errors in measured numbers.  Oocytes per worm is the sum of the 
unfertilized eggs laid and those found in the gonad when fixed.  The 
total sperm and progeny yield in this experiment were slightly lower 
than the 280/worm that we normally observe.
It is apparent from Table 1 that the efficiency of sperm utilization 
is nearly 1.  That is, every sperm normally fertilized an egg.  Not 
every oocyte is fertilized because the worm produces about 100 more 
oocytes than sperm.  That sperm are not synthesized after early 
adulthood was confirmed by the complete absence of the densely 
staining 'meiotic precursor' cell nuclei that mark the maturation of 
sperm from meiotic pachytene to spermatids in hermaphrodites and males.

These results were slightly surprising because it can be readily 
observed with Nomarski optics on live worms or on Feulgen stained 
preparations that sperm are carried out of the spermatatheca by the 
oocytes passing through.  If all these sperm subsequently participate 
in fertilization, they must be able to fertilize oocytes outside of 
the spermatatheca or they must be able to swim back to the 
spermatatheca.  We favor the latter hypothesis and are testing it for 
both hermaphrodite and male sperm.

Figure 1