The generation of diploid spermatozoa is essential for the continuity of
tetraploid lineages. The
DNA content of diploid spermatozoa from allotetraploid hybrids of red crucian carp and common carp was nearly twice as great as that of haploid spermatozoa from common carp, and the durations of rapid and slow progressive motility were longer. We performed comparative proteomic analyses to measure variations in
protein composition between diploid and haploid spermatozoa. Using two-dimensional electrophoresis followed by liquid chromatography tandem mass spectrometry, 21
protein spots that changed in abundance were analyzed. As the common carp and the allotetraploid hybrids are not fully sequenced organisms, we identified
proteins by Mascot searching against the National Center for Biotechnology Information non-redundant (NR) protein database for the zebrafish (Danio rerio), and verified them against predicted homologous
proteins derived from transcriptomes of the testis. Twenty
protein spots were identified successfully, belonging to four gene ontogeny categories: cytoskeleton, energy metabolism, the
ubiquitin-
proteasome system, and other functions, indicating that these might be associated with the variation in diploid spermatozoa. This categorization of variations in
protein composition in diploid spermatozoa will provide new perspectives on male
polyploidy. Moreover, our approach indicates that transcriptome data are useful for proteomic analyses in organisms lacking full
protein sequences.