Motility, fertility and ultrastructural changes of ...
|Title||Motility, fertility and ultrastructural changes of ocean pout (Macrozoarces americanus L.) sperm after cryopreservation|
|Author(s)||Z. Yao, L. W. Crim, Gavin F. Richardson, C. J. Emerson|
|Abstract||The possibility of long term storage, by cryopreservation in liquid nitrogen, of spermatozoa of ocean pout (Zoarces americanus) and the changes in motility, fertility and ultrastructure of the spermatozoa after freezing and thawing were examined. Four cryoprotectants, including DMSO, and 3 semen diluents (A, B and C) were tested for their influence on sperm motility. Since fresh spermatozoa displayed the highest motility in diluent C, which had the closest chemical composition to that of the seminal plasma of ocean pout this solution with DMSO (C-DMSO) was chosen as a diluent for ocean pout semen cryopreservation. Fresh semen was diluted in 3 volumes of C-DMSO, transferred into 0.25- or 1.7-ml straws, then frozen in liquid nitrogen vapour. When the internal temperature of the straws had dropped to -95 degrees C, the straws were plunged into liquid nitrogen. The frozen semen was thawed in a water bath at 1 or 30 degrees for 30 and 7 s respectively. The presence of DMSO in semen extender was essential for protecting the spermatozoa and 20% DMSO (v/v) yielded the highest post-thaw sperm motility (20-25% of the total cells). An average freezing rate of 9 degrees /min during the initial freezing phase (in liquid nitrogen vapour) resulted in higher post-thawed sperm motility than faster (18 degrees /min) and slower (6 degrees /min) freezing rates. Thawing frozen semen in water at 30 or 1 degrees did not cause any difference in terms of sperm motility. It is suggested that the loss of sperm motility during freezing and thawing is due to ultrastructural changes in spermatozoa (severe swelling of the mitochondria or dehydration of cytoplasm at the midpiece) which were detected by scanning electron microscopy. In vitro AI of fresh ova using thawed semen yielded a fertilization rate of 33% compared with 48-58% from fresh semen..|
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