Worm Breeder's Gazette 10(2): 63

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.

Sperm Fusion

Diane C. Shakes and Samuel Ward

While analyzing a large number of videotapes of in vitro 
spermiogenesis, a rare event (never before seen) of sperm fusion was 
observed.  Spherical spermatids, which have been treated with 
triethanolamine to initiate spermiogenesis, pass through an 
intermediate stage during which they twirl and extend multiple, long, 
thin spikes before they form the single motile pseudopods of the 
mature spermatozoa.  In this particular case, two adjacent cells which 
began twirling at the same time, fused together during this 
intermediate stage.  The fused cells rounded up into a single large 
cell and then formed a double-sized spermatozoa with a single 
pseuodpod.  This spermatozoa was able to translocate across the glass 
slide and crawled outside the field of video screen.
The observation was made with spe-8 male sperm, but since these 
males are fertile, we believe that the fusion could occur in wild type 
spermatids as well.  The formation of a double-sized spermatozoa with 
a single rather than a double pseudopod suggests that the polarity of 
the spermatozoa develops during spermiogenesis rather than during the 
budding of the spermatids in meiosis.  The large, but normal-looking 
spermatozoan also demonstrated the regulative capacity to compensate 
for the difference in cell surface/volume ratio.
If the frequency of sperm fusion could be enhanced, e.g.  with PEG 
or electroporation, it could lead to a number of interesting studies.  
We could test the regulative capacity of sperm to see how large a 
spermatozoa can be formed.  Sperm fusion could also be used to test 
for cytoplasmic rescue between spe (spermatogenesis defective) mutant