Sublethal damage during cryopreservation of rainbow trout sperm

Area of Science:

• Aquatic Biology
• Reproductive Biology
• Cryobiology

Background:

• Cellular damage during fish sperm cryopreservation is known.
• A correlation between cryodamage and fertility rates is often unclear.
• Sublethal cryodamage may affect sperm functionality, especially in hypoosmotic fertilization environments.

Purpose of the Study:

• To investigate changes in freshwater fish sperm cell permeability after cryopreservation.
• To assess the impact of cryoprotective agents and egg yolk on sperm survival in hypoosmotic conditions.
• To correlate cryodamage with sperm functionality and fertility.

Main Methods:

• Sperm permeability was assessed using Hoechst 33258.
• Sperm samples were cryopreserved using different cryoprotective agents (Me2SO, DMA, methanol) and cooling rates.
• The protective effect of egg yolk as a membrane stabilizer was evaluated.
• Sperm survival was tested after dilution in hypoosmotic media.

Main Results:

• Freezing and thawing dramatically increased sperm fragility in hypoosmotic solutions.
• Cryoprotective agents slightly increased susceptibility to damage, but Me2SO yielded the best results.
• Egg yolk significantly enhanced sperm membrane protection and prolonged survival in fertilization media.

Conclusions:

• Sublethal cryodamage to the sperm membrane, undetected by standard methods, impacts fertility.
• Egg yolk is a crucial additive for improving cryopreserved fish sperm viability.
• Me2SO is a promising cryoprotective agent for freshwater fish sperm.