Cryopreservation of strip spawned sperm using non-programmable freezing technique in the blue musselMytilus galloprovincialis

In this study, a non-programmable freezing technique has been developed with the strip spawned blue mussel (Mytilus galloprovincialis) sperm. The key parameters optimized including (1) cryoprotectant agents (CPAs); (2) cooling temperature; (3) thawing temperature; (4) sugar and amino acid supplementation and (5) sperm to egg ratio. The fertilization rate and/or integrity of plasma membrane and acrosome were used as sperm quality assessment indicators. The highest post-thaw sperm fertilization rate of 95% was achieved, when sperm were cryopreservated in 8% dimethyl sulfoxide at 7.8 cm above the liquid nitrogen surface and thawed in a 60°C seawater bath. The addition of glucose, sucrose or trehalose in dimethyl sulfoxide did not, whereas 0.8% glycine did significantly improve the post-thaw sperm fertilization rates. The fluorescent evaluation has demonstrated that the addition of glycine significantly improved the post-thaw sperm acrosome integrity, revealing a positive role of glycine in the improvement of post-thaw sperm quality in blue mussels.