Seminal quality and global proteomic analysis of spermatozoa from captive Amazon squirrel monkeys (Saimiri collinsi Osgood, 1916) during the dry and rainy seasons

The squirrel monkey (Saimiri collinsi), a Neotropical primate endemic to the Amazon in Brazil, is used as a biological model for reproductive research on the genus Saimiri. Although this animal is known to exhibit reproductive seasonality, nothing is known about the differences in its seminal quality, sperm protein composition, or sperm protein profile between the breeding (dry) and non-breeding (rainy) seasons. Thus, the aims of this study were to evaluate the quality of S. collinsi semen during the dry and rainy seasons and to describe the global sperm proteomics and expression variations in the sperm proteins during the two seasons. Aside from the pH, there was no difference in the seminal quality between the dry and rainy seasons. The study approach based on bottom-up proteomics allowed the identification of 2343 proteins present in the sperm samples throughout these two seasons. Of the 79 proteins that were differentially expressed between the two seasons, 39 proteins that were related to spermatogenesis, sperm motility, capacitation, fecundation, and defense systems against oxidative stress were upregulated in the dry season. Knowledge on the sperm proteins provides crucial information for elucidating the underlying mechanisms associated with sperm functionality. Thus, our results help to advance our understanding of the reproductive physiology of S. collinsi, providing valuable information for the improvement of protocols used in assisted reproduction techniques for the conservation of endangered Saimiri species.