ADVANCEMENTS AND CHALLENGES IN CRYOPRESERVATION OF FRESHWATER FISH SPERM: A REVIEW

Cryopreservation is a standard preservation method at very low temperatures that can help conserve genetic diversity in fish by allowing the long-term conservation of gametes. Cryopreservation of freshwater fish sperm plays a vital role in aquaculture, conservation, and management of genetic resources. Cryoprotectants play an essential role in reducing injuries to sperm cells caused by freezing, such as the formation of ice crystals, disruption of membranes, mitochondrial dysfunction, and oxidative stress. Usually, two types of cryoprotectants are used, i.e., PCP or penetrating cryoprotectants, which enter through the cell membranes, and NPCP or nonpenetrating cryoprotective agents, which exert their action extracellularly. However, the problems of cryoprotectant toxicity and species-specific responses call for establishing protocols specific to fish species. Cryopreservation success in fish depends on the correct combination of selected cryoprotectant type and appropriate concentration that can enhance post-thaw sperm viability and fertility. This review covers recent advances, challenges, and practical approaches toward cryopreservation to guarantee the successful preservation of freshwater fish sperm.