Global assessment of wildlife cryopreservation reveals major taxonomic gaps and strong species-specific differences in mammalian sperm cryotolerance

Currently, global conservation efforts for wildlife focus on a limited number of cell types and species. Although protocols from domestic and non-threatened related species have been applied to endangered species, cryopreservation techniques are species-specific and are constrained by a lack of understanding of reproductive biology in these species. Based on a review of 126 original studies from 27 countries, encompassing 160 species, we assess the current state of cryopreservation in wildlife, including gametes, embryos, somatic cells, and various tissues. Furthermore, we focused on the most homogeneous and frequently studied cell type in wildlife cryobanking: mammals sperm.. A meta-analysis of 27 studies was conducted to examine species-specific and protocol-dependent factors that affect post-thaw sperm quality.

Our findings provide quantitative estimates of cryopreservation for various cell types and tissues in wildlife taxa. Furthermore, they serve as a crucial research roadmap, identifying major challenges in cryopreservation and proposing solutions.