Freeze preservation of squirrel monkey sperm for use in timed fertilization studies.

These investigations were concerned with the response of squirrel monkey sperm to freezing. A procedure involving preincubation at 37 degrees C, progressive cooling combined with a two-step dilution, and freezing on Dry Ice was applied to semen samples collected by electroejaculation from two animals. Sperm concentrations in these samples were 321.8 X 10(6)/ml (+/-204.1 SD) and 532.8 X 10(6) ml (+/-117.1 SD), respectively. Sperm motility prior to freezing was 68.1% (+/- 15.9 SD) AND 63.6% (+/-14.8 SD). Following freezing and thawing, motilities of 53.8% (+/-17.1 SD) and 51.8% (+/-22.9 SD) were observed. The freezing procedure increased sperm motility in approximately 30% of samples from both animals. Changes in the motile behavior of sperm were not observed after freezing. Serum testosterone measurements, the first made in the squirrel monkey, gave values similar to those obtained for other primates. A progressive decline in testosterone concentration, seen in both animals during the course of these investigations, did not affect semen characteristics or the response of sperm to freezing.