Abstract
The volumes of sperm heads were estimated from three-dimensional reconstructions of serially sectioned bundles of nearly mature spermatid nuclei. Cysts from males in which all sperm are expected to have comparable amounts of chromatin (X/Y and In(3LR)/+) show unimodal frequency distributions of nuclear volumes, whereas cysts from males in which meiotic segregation is expected to deliver unequal amounts of chromatin material to spermatid nuclei show two (XY/O and XY/Y) or more (T(2;3)/+ and C(2L);C(2R)) modes. The mean volumes of the subpopulations in these cases are related in the same proportions as the metaphase lengths of their chromosomal complements. Thus the volumes of sperm nuclei are proportional to their DNA content. Sperm head shape, on the other hand, does not appear to be very sensitive to chromosomal constitution, as heads of different size do not vary greatly in shape.—The numbers of sperm heads in the various size classes in a cyst depart from mendelian expectations; these departures are caused by the elimination, during individualization, of chromosomes contained within micronuclei that are formed in spermatids at the end of the second meiotic division. The effect of this chromosome loss is to increase the proportion of nullosomic gametes in the sperm pool.—The relative frequencies of XY-bearing and nullo-X, nullo-Y sperm in XY/O males were estimated from the volume measurements. Taking this estimate as a measure of the fertilizing population, it is possible to infer from the change in sex ratio over time following insemination, that XY-bearing sperm have an advantage of 1.5 over nullo-X, nullo-Y sperm in leaving the seminal receptacle of the female for fertilization of ova.
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Selected References
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- Novitski E., Sandler I. ARE ALL PRODUCTS OF SPERMATOGENESIS REGULARLY FUNCTIONAL? Proc Natl Acad Sci U S A. 1957 Apr 15;43(4):318–324. doi: 10.1073/pnas.43.4.318. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Olivieri G., Tanzarella C. The influence of the nucleolar organizer region on sperm utilization in Drosophila melanogaster. Mol Gen Genet. 1973 Jul 31;124(1):51–56. doi: 10.1007/BF00267163. [DOI] [PubMed] [Google Scholar]
- PEACHEY L. D. Thin sections. I. A study of section thickness and physical distortion produced during microtomy. J Biophys Biochem Cytol. 1958 May 25;4(3):233–242. doi: 10.1083/jcb.4.3.233. [DOI] [PMC free article] [PubMed] [Google Scholar]
- PEACOCK W. J. NONRANDOM SEGREGATION OF CHROMOSOMES IN DROSOPHILA MALES. Genetics. 1965 Apr;51:573–583. doi: 10.1093/genetics/51.4.573. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rasch E. M., Barr H. J., Rasch R. W. The DNA content of sperm of Drosophila melanogaster. Chromosoma. 1971;33(1):1–18. doi: 10.1007/BF00326379. [DOI] [PubMed] [Google Scholar]
- Tokuyasu K. T., Peacock W. J., Hardy R. W. Dynamics of spermiogenesis in Drosophila melanogaster. I. Individualization process. Z Zellforsch Mikrosk Anat. 1972;124(4):479–506. doi: 10.1007/BF00335253. [DOI] [PubMed] [Google Scholar]