Cryopreservation and Quality Assessment of Fish Sperm

Cryopreservation of fish sperm enables long-term storage of genetic resources for aquaculture, conservation and selective breeding. The process typically involves dilution in a tailored extender, addition of a cryoprotectant to limit ice crystal formation, controlled cooling and storage in liquid nitrogen. Key challenges include osmotic shock, membrane damage, oxidative stress and potential epigenetic alterations during freezing and thawing. Quality assessment integrates quantitative measures of sperm motility, viability, plasma-membrane integrity and DNA integrity, often using computer-assisted sperm analysis and flow cytometry. Emerging focus areas encompass the impact of reactive oxygen species on cell function, the optimisation of bio-derived cryoprotectants and the subtle effects of cryopreservation on DNA methylation patterns. Improvements in protocol design have broad implications for maintaining biodiversity, enhancing hatchery outputs and securing broodstock genetics worldwide.

Research from Nature Portfolio

A recent study evaluated three common cryoprotectants—dimethyl sulfoxide, methanol and glycerol—in rainbow trout sperm. Dimethyl sulfoxide best preserved post-thaw motility and fertilisation capacity, while methanol offered moderate protection and glycerol was least effective. Reduced representation bisulfite sequencing revealed only minor changes in DNA methylation, with a few hundred differentially methylated cytosines depending on the cryoprotectant. These findings indicate that optimised cryoprotectant selection can minimise epigenetic perturbation and inform risk assessment for progeny derived from cryopreserved sperm.

Cryopreservation and Quality Assessment of Fish Sperm publication trend

The graph below shows the total number of articles in cryopreservation and quality assessment of fish sperm across all publications each year (not limited to Nature Index journals).

Technical terms

Cryopreservation: A process of cooling and storing cells at ultra-low temperatures to halt biological activity and preserve viability.

Cryoprotectant: A chemical agent (e.g. dimethyl sulfoxide, glycerol) that reduces ice crystal formation and osmotic stress during freezing.

Extender: A buffered solution containing salts, nutrients and sometimes antibiotics, used to dilute and protect sperm prior to freezing.

Sperm motility: The capacity of spermatozoa to move actively, commonly quantified by velocity and trajectory parameters.

DNA methylation: An epigenetic modification involving addition of methyl groups to cytosine bases, which can regulate gene expression.

Ice recrystallisation inhibition (IRI): The ability of certain molecules (e.g. antifreeze proteins) to prevent growth of ice crystals during thawing.

References

1. Short‐term storage of sperm in common carp from laboratory research to commercial production—A review. Reviews in Aquaculture (2023).
2. Intermediate-Term Storage of Spotted Halibut (Verasper variegatus) Sperm: Effects of Storage Methods, Extenders Supplemented with Antibiotics and Antioxidants on Sperm Quality. Antioxidants (2023).
3. Novel Apoplastic Antifreeze Proteins of Deschampsia antarctica as Enhancer of Common Cell Freezing Media for Cryobanking of Genetic Resources, a Preliminary Study. Biomolecules (2024).
4. Cryopreservation effect on DNA methylation profile in rainbow trout spermatozoa. Scientific Reports (2023).