 The study examined the differences between catalyac and yak testes, focusing on the single-cell transcriptome sequencing of both species. The results showed that catalyac had a higher rate of miotic arrest than yaks, which could explain why catalyac are infertile. Additionally, the study also found that catalyac spermatogonial cells were more sensitive to environmental stresses, such as low temperature or high humidity, compared to yak cells. This suggests that catalyac spermatogonial cells have a lower tolerance to environmental stresses, which could further explain their infertility.