Twelve semen samples were collected from six adult male black-and-gold howler monkeys (Alouatta caraya) from the National Primate Center, Ananindeua, PA, Brazil, during the summer of 2014. Males were between 5 and 9 years old. Collections were done by rectal probe electroejaculation and samples were immediately diluted in Ringer lactate solution. The sperm suspension was, then, diluted 1:10 in 10% formol saline solution. A drop of fixed sperm was placed on a microscope slide under a coverslip and 200 cells were assessed using a Differential interference contrast (DIC) microscope. Results are shown as mean ± SD (minimum-maximum). There were 38.01 ± 12.9% (19.86-58.00%) major defects and 18.59 ± 6.02% (10.00-32.00%) minor defects. Coiled tail (7.65 ± 6.8%) and abnormal midpiece (6.29 ± 3.66%) were the most common major defects, while narrow head (4.27 ± 3.13%) and oblique implantation of the tail (2.69 ± 1.7%) were the most common minor defects. In addition to the defects described for domestic species and human sperm, we observed a new defect. In all ejaculates, there was a defect in which the head was laterally attached to the midpiece. We called it “lateral implantation of the head”, and considered it a major defect. Although some of these sperm had tail motility during motility analysis, it was not progressive. The percentage of affected sperm was 2.79 ± 2.24% (0.48-9.0%). There are two other studies on sperm morphology of this species, which reported a total of 37.5%¹ and 21.4%² abnormal sperm, values much lower than what we obtained in this study. Further investigations on this new defect are underway.

Acknowledgements: We would like to thank the São Paulo Research Foundation (FAPESP) for the financial support.