Quality change of Pagrus major sperm after long-term cryopreservation
长期超低温保存后真鲷精子的质量变化

After cryopreservation (1-73 months), the quality of Pagrus major sperm, which was cryopreserved from 2003 to 2009 in 5 batches, was examined by observing motility, fertilization rate and ultrastructures. The cryopreserved sperm were thawed in 40 oC water bath for 100~110 s. After activation with seawater, the motility of the sperm was estimated; 6-8 h after artificial fertilization, fertilization rate was examined; and after being fixed with by 2.5% glutaraldehyde, the ultrastructure of sperm was studied with scanning electron microscope and transmission electron microscope. The highest motility (87.67%±2.52%) and fertilization rate (71.33%± 8.84%) were obtained in sperm after a 1-month cryopreservation, even though they were not significantly different from those of the sperm after a 13-month or and 26-month cryopreservation (P>0.05). After a 48-month cryopreservation, the motility and fertilization rate decreased significantly in comparison with those of sperm after a 1-month cryopreservation (P<0.05). The lowest motility (50.67% ± 5.31%) and fertilization rate (39.56% ± 0.69%) were obtained in sperm cryopreserved for 73 months; main ultrastructural damage was observed in the head, mitochondria and membranes of sperm.