Abstract: Frozen sperm of animals has great advantages such as long-term storage,long-distance transport,and more safety and efficiency.So,it has been broadly applicated in the fields of animal genetic resources preservation,endangered species protection,and cross-regional breeding of livestock and poultry.Sperm,as a highly differentiated cell,undergoes varying degrees of structural damage during the freezing process.These damages affect the integrity,fluidity,and selective permeability of sperm membrane,as well as alter the composition and function of membrane lipids,proteins,RNA,and other molecules.Consequently,these changes directly impact the post-thaw viability of sperm.Additionally,the extent of sperm cryotolerance varies greatly due to factors such as species,variety,season,and nutrition.However,due to the lack of clear understanding of basic problems such as sperm cryodamage,cryotolerance,and its influencing factors,the present freezing technology cannot produce frozen sperm that has high enough quality and can be applied in farm except bull.This has posed significant challenges to the preservation of these animal genetic resources via frozen semen,as well as to genetic improvement and the development of new breeds through artificial insemination using frozen semen.Therefore,enhancing the further basic research on the pertinent issues and developing an efficient freezing system to minimize freezing-induced damage and improve post-thaw sperm viability would have a positive impact on the promotion and application of the technology.The authors summarize the recent research progress on the mechanisms of sperm cryodamage and differential cryotolerance in animals,so as to provide reference for the in-depth development of related research.

Key words: animal; sperm; cryopreservation; cryodamage; differential cryotolerance