The purpose of the study was to analyze seminal plasma composition, sperm production, and sperm motility over the course of the spawning season in the common carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss). The highest mean percent of motile sperm (carp, 98.3 ± 1.6%; rainbow trout, 92.8 ± 5.6%) and highest spermatozoon velocity (carp, 286.3 ± 7.8 μm sec-1; rainbow trout, 245.3 ± 8.3 μm sec-1) were observed in the middle phase of the spawning period, at 5 sec post-activation. Sperm volume and concentration increased in the early spawning period, then decreased significantly toward the end of the season in both species. Seminal plasma osmolality was 262-270 mOsmol kg-1from carp and 232-248 mOsmol kg-1from rainbow trout, with little variation over the spawning period. Protein concentration in carp seminal plasma was stable throughout the reproductive season, whereas the highest protein level (2.1 ± 0.3 mg mL-1) in rainbow trout was observed in the middle phase of the spawning period. Seminal plasma composition in both species was analyzed using two-dimensional polyacrylamide gel electrophoresis combined with mass spectrometry. Thirteen differentially expressed protein spots in carp seminal plasma and sixteen spots in rainbow trout seminal plasma varied over the course of the reproductive season. The unique proteins identified are involved in the regulation of spermatogenesis, sperm motility, maintenance of sperm membrane lipid stability, and antioxidant protection. These results provide a deeper understanding of the role of fish seminal plasma proteins as well as a list of novel markers of sperm quality. Mol. Reprod. Dev. 83: 968-982, 2016 © 2016 Wiley Periodicals, Inc.

Faculty of Fisheries and Protection of Waters Research Institute of Fish Culture and Hydrobiology South Bohemian Research Center of Aquaculture and Biodiversity of Hydrocenoses University of South Bohemia in České Budějovice Vodňany Czech Republic

Faculty of Science Department of Chemistry and Biochemistry University of South Bohemia in České Budějovice České Budějovice Czech Republic

Faculty of Science Department of Chemistry and Biochemistry University of South Bohemia in České Budějovice České Budějovice Czech Republic Institute of Parasitology Biology Centre of Academy of Sciences of the Czech Republic České Budějovice Czech Republic

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