MORPHOLOGICAL REACTION OF SPERMATOZOA IN THE FEMALE REPRODUCTIVE TRACT OF THE RABBIT

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Abstract
A study of rabbit ejaculate and epididymal spermatozoa, and of spermatozoa recovered from various regions of the female tract, has revealed some consistent morphological differences in the state of the acrosome between these groups. Few acrosomes were missing or changed in epididymal or ejaculate spermatozoa. On the other hand, the acrosome was absent in spermatozoa released from the perivitelline space of fertilized ova. Uterine and tubal spermatozoa recovered 9 to 11 hr after insemination of ejaculates into oestrous or pseudopregnant females showed change or loss of the acrosome in a variable percentage (8 to 58%). The percentage acrosome loss from uterine samples taken after insemination of aliquots from the same ejaculate into pairs of females was closely similar within each pair, though variation occurred between pairs. Consistently higher acrosome losses (mean, 33%) were found following insemination of ejaculates collected after 1 month''s sexual rest than were found after insemination of the third ejaculate from each of the same males (mean. 17.2%). Considerably fewer acrosomes were missing from uterine spermatozoa recovered after insemination of epididymal spermatozoa (mean, 5%) compared to the loss after insemination of ejaculate spermatozoa (mean, 27.4%) taken previously from the same males. Fertility trials with ejaculate and epididymal spermatozoa showed no difference in fertilization rate, or in numbers of supplementary spermatozoa, in favour of the ejaculate samples, i.e. those which showed the greater percentage acrosome changes. In conclusion it is suggested that the quantitative variation in acrosome reaction between samples of uterine spermatozoa reflects differences in the samples, rather than differences in the female environment. The acrosome changes in the uterine and tubal spermatozoa of the domestic rabbit are probably not a morphological concomitant of capacitation, but more probably reflect impending sperm senility.