Evaluation of the prosimian Galago senegalensis as a laboratory primate for in vitro studies on early gamete interactions

The small prosimian, Galago seneqalensis, was evaluated for use as a laboratory primate for in vitro studies of fertilization. The lesser galago is hardy, can breed in captivity, is easy to handle and does not require special housing accommodations. Viable spermatozoa were obtained from galago males by electroejaculation using a rectal probe. Galago spermatozoa have a hook-like acrosome which is discernible with the phase-contrast microscope. Thus, the acrosome reaction of living spermatozoa can be observed in vitro. Acrosome reactions of galago spermatozoa occurred in vitro in hamster cumulus masses (ova present) and in heat pretreated human, galago, guinea pig and rabbit sera. Dialysis of human blood serum did not separate discrete factors necessary for the motility of galago spermatozoa but did decrease the number of acrosome reactions. The vaginal orifice of the female galago is open only during estrus. This visible sign of estrus was correlated to the time of ovulation through surgical examination of ovaries, thus providing a simple means for predicting ovulation time to recover preovulatory and recently ovulated ova for experimental use. Only one ovum is normally ovulated per cycle, but low dosages of Pregnant Mare Serum Gonadotrophin (20-40 IU) were found to stimulate follicular growth with a low incidence of atresia (14.6%; 11 of 75 ova). Freshly ejaculated spermatozoa with intact acrosomes did not penetrate zona free hamster ova or galago follicular ova. However, penetration in both instances was effected with galago spermatozoa capacitated by preincubation 7-8 hr in human blood serum. These sperm suspensions exhibited a high incidence of acrosome reactions (60-80%). Reproductive cycles of the galagos in this study did not appear to be seasonal. Both spermatozoa and ova were recovered during each month of the calendar year. The gamete and reproductive characteristics of the lesser galago, as observed in this study, clearly indicate its greater potential for in vitro studies of fertilization than the more commonly used laboratory primate species.