The Influence of Sperm Origin on Function, Preservation and Embryo Development in South American Camelids

South American camelids (SAC), including llamas (Lama glama) and alpacas (Vicugna pacos), exhibit distinctive reproductive features, such as induced ovulation and highly viscous seminal plasma (SP), that complicate conventional semen collection and objective sperm evaluation. Consequently, spermatozoa recovered from the cauda epididymis or through surgical vas deferens deviation (VDD) have become valuable alternatives for research and germplasm preservation. These sperm sources also provide a unique opportunity to investigate sperm physiology in the absence of SP. This review critically compares the functional characteristics of ejaculated, epididymal and VDD-derived spermatozoa and examines how methodological variables, including collection procedures, post-mortem interval, tissue handling and surgical protocols, contribute to variability among studies. Current evidence indicates that many functional differences observed among sperm sources, particularly in motility and plasma membrane functionality, are largely associated with the presence or absence of SP rather than intrinsic differences in sperm quality. These findings support a reinterpretation of SP as a physiological regulator of sperm quiescence, membrane stability and functional competence rather than merely a technical obstacle. We also review advanced analytical approaches, including flow cytometry and imaging flow cytometry, highlighting their potential to improve the evaluation of camelid sperm physiology and cryobiology, while summarizing current evidence on the developmental competence of sperm from different anatomical sources for in vitro embryo production. Overall, this review provides an updated synthesis of the literature, identifies major methodological limitations and highlights priorities for future research to advance reproductive biotechnologies in SAC.