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.
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] Table Legend: 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.