Novos parâmetros para avaliação andrológica em macaco-de-cheiro (Saimiri collinsi Osgood, 1916): distância anogenital, micromorfologia e perfil proteico espermático.

Abstract

The squirrel monkey (Saimiri collinsi), a Neotropical primate endemic to the Amazon in Brazil, with a remarkable but little studied free-living reproductive seasonality. Recently this species was adopted as an experimental biological model for reproductive research on the genus Saimiri, contributing to the conservation of these animals. To better understand the reproductive physiology of the genus Saimiri, this study aimed to (i) to evaluate the correlation between anogenital distance with sperm parameters and reproductive hormones (estradiol and testosterone) in squirrel monkeys (S. collinsi); (ii) describe the micromorphological and ultrastructural characteristics of spermatozoa from squirrel monkeys (S. collinsi) through scanning and transmission electron microscopy; (iii) characterize the protein profile of squirrel monkeys sperm (S. collinsi); (iv) associate the expression of sperm proteins and the sperm characteristics of squirrel monkey (S. collinsi). The study approach based on bottom-up proteomics (Shotgun 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. The SEM electromyrographies revealed a normal Saimiri collinsi’s sperm measure 71.73±0.71 μm with lateral tail insertion, a paddle-shaped flattened head and a acrosome occupied most of the head, and completely, the TEM also showed that the middle piece is characterized by a central 9 + 2 microtubule axoneme surrounded by nine dense fibers, and the mitochondria were juxtaposed forming the mitochondrial sheath. Anogenital distance was correlated with seminal volume, sperm motility, vigour, and plasma membrane integrity, but not with body weight, reproductive hormones, and testicular volume. 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.