Application of Glucose-Methanol Extender to Cryopreservation of Mozambique Tilapia (Oreochromis mossambicus) Sperm
2019
Ugwu, Stanley Ifeanyi | Kowalska, Agata | Morita, Masaya | Kowalski, Radoslaw Kajetan
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.
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