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.
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 spermatids.