Studies on cryopreservation of early stage zebrafish (Danio rerio) oocytes using controlled slow cooling
AuthorsNwankwo, Judith N.
MetadataShow full item record
AbstractIn the last three decades, much effort has been made toward the successful cryopreservation of fish gaments. The spermatozoa from many species including salmonid, cyprinids, and acipenseridae has been successfully cryopreserved and well documented. Systematic studies on fish oocytes cryopreservation has not been carried out until recently. In this study, the effect of cryoprotectant toxicity on stage I and II zebrafish oocytes were studied and the controlled slow cooling was used at different cooling rates to identify the optimal cooling rate for these oocytes and the optimal conditions for removing cryoprotectant. Methanol was found to be the least toxic CPA for zebrafish oocytes and 4M methanol in potassium chloride (KCI) buffer was used as the cryoprotective solution. Oocytes were cooled with programmable cooler (Planner KRYO 550) using controlled slow cooling at 0.3, 0.5 and 1°C/min rates, combined with seeding at -12.5°C and plunge into liquid nitrogen at -80°C. 1°C/min was identified to be the optimal condition for cryopreservation of stage I and II oocytes. High survival rate were obtained after cooling to -196°C assessed with TB staining which were 87.8 ± 4.9% and 86.8 ± 6.5% for stage I and II respectively. It was also found in this study that recovery conditions affect oocyte survivals after freezing. Oocytes which had been incubated for 60 or 120min in room temperature showed higher survival rate than those assessed immediately after freezing. This study has shown that stage II (cortical alveoli stage) oocytes were more resistible to freezing than stage I (primary growth stage) oocytes. More oocytes viability studies are needed to validate these results.
PublisherUniversity of Bedfordshire
TypeThesis or dissertation
DescriptionA thesis submitted to the University of Bedfordshire in accordance with requirements for the degree of Master of Science by Research
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