ABSTRACT
BACKGROUND: It is unknown whether male black-handed spider monkeys (Ateles geoffroyi) undergo a reproductive decline as they age. The purpose of this work was investigating whether serum testosterone and semen quality decrease with age in these primates as occur in other species. METHODS: In this study, we assessed age variations in the concentration of serum testosterone, sperm counts, and motility in nine males. We took serum blood samples and semen samples by electroejaculation of anesthetized males throughout the fertile season. RESULTS: We found that testosterone levels and total sperm concentration, motile, progressive, fast linearly moving, medium linearly moving, slow linearly moving and immotile sperm significantly decreased with age. CONCLUSIONS: Our results show that a reproductive decline occurs in male spider monkeys because of a decrease in sperm counts. These results are similar to those of rhesus monkeys and men, despite the phylogenetic distance between New and Old World primates.
