Sperm cryopreservation of yellow drum Nibea albiflora: A special emphasis on post-thaw sperm quality

This study was intended to develop an optimal sperm cryopreservation protocol for yellow drum (Nibea albiflora), a commercially important fish species in East Asia. Specifically, we evaluated cryoprotectant type, concentration, and cooling rate and found that the highest fertilization (56–61%) and hatch (42–47%) can be obtained from yellow drum sperm suspended in 5% ethylene glycol or 10% dimethyl sulfoxide, cooled at 220 °C/min, thawed in 40 °C water bath for 7 s, and fertilized with fresh (non-frozen) eggs at a sperm-to-egg ratio of 107. We also compared other sperm quality parameters such as sperm motility, motility duration, membrane integrity, mitochondrial membrane potential, and DNA fragmentation between fresh and thawed sperm samples. Although cryopreservation resulted in a significant increase in DNA fragmentation and significant decreases in the remaining parameters, the magnitude of these changes was small when compared to the 2000 to 3000-fold reduction in fertilization/hatch capability of thawed sperm. These findings suggest possible disruption of signaling pathways that cannot be detected by conventional quality assays. Further analysis of sperm membrane lipid composition revealed a significant negative correlation between sperm quality and cholesterol-to-sphingomyelin ratio. These findings indicate that lipid rafts could be the main targets for cryodamage-induced decrease in fertilization capability of thawed sperm. Future studies are necessary to further explore the role of lipid rafts in cryopreservation-mediated damage in fish sperm.

► We evaluated sperm cryopreservation in yellow drum (Nibea albiflora).
► Sperm can be cryopreserved with 5% EG or 10% DMSO at a cooling rate of 220 °C/min.
► Thawed sperm exhibited mild adverse effects on conventional quality criteria.
► Thawed sperm exhibited dramatic reduction in fertility and hatch rate.
► Post-thaw sperm quality correlated negatively with cholesterol-to-sphingomyelin ratio.