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¹ University of the Ryukyus, Sesoko Station, Tropical Biosphere Research Center, Okinawa 905-0227, Japan
² Department of Aquaculture, Stanisław Sakowicz Inland Fisheries Institute, Oczapowskiego 10, Olsztyn 10-719, Poland
³ Institute of Animal Reproduction and Food Sciences, Polish Academy of Sciences, Olsztyn 10-747, Poland DOI : 10.4194/1303-2712-v19_01_05 Viewed : 4205 - Downloaded : 2974 Cryopreservation of fish sperm offers key advantages in genetic improvement and can be used to preserve threatened and endangered fish species or strains. The use of simple cryoprotective media facilitates cryopreservation procedures. In this study, we used a glucose-methanol extender for cryopreservation of Oreochromis mossambicus sperm. Optimal cryopreservation conditions were found to be 175 mM glucose and 12.5% methanol at 1:8 dilutions (sperm: extender), 60 min equilibration after dilution and pre-freezing at 8 cm above liquid nitrogen. Cryopreservation at these conditions resulted in ~ 50% decrease in post-thaw sperm motility (27 - 28% post-thaw motility compared to the 62% fresh control motility). However, fertilization rate of cryopreserved sperm reached 49% for sperm diluted 10 times, and 52% for 8 times diluted sperm. These rates were comparable to fertilization rate (56%) obtained using fresh sperm. Our results, therefore, reveal that even though the progressively motile sperm and motility percentage decreased significantly after cryopreservation, the fertilizing ability of cryopreserved sperm was not significantly affected. Our results show that glucose-methanol mixture is not only suitable for cryopreservation of O. mossambicus sperm but also allows cryopreservation in small volumes as low as 10 µl. Keywords : Fertilization, CASA, Equilibration, Motility