SELECTION AND UTILIZATION OF SPERMATOZOA IN THE REPRODUCTIVE-TRACT OFTHE FEMALE ZEBRA FINCH TAENIOPYGIA-GUTTATA

The numbers and proportion of spermatozoa reaching different parts of the female reproductive tract after a single natural insemination were investigated in zebra finches Taeniopygia guttata. The number of sper matozoa transferred during a single, natural copulation was estimated by comparing the number of spermatozoa in the seminal glomera of males that had performed a single copulation with control males. The mean n umber of spermatozoa per ejaculate was 5.8 x 10(6) +/- 1.80 x 10(6) SE W. The mean number of spermatozoa stored in the sperm storage tubules in the uterovaginal junction following a single, natural insemination was 6027 +/- 1874, 0.104% of those inseminated. The mean number of spe rmatozoa reaching the infundibulum and trapped on the perivitelline la yer of all eggs of the clutch after a single copulation was 45.6 +/- 9 .18 and a further 36 penetrated the perivitelline layer of the ovum, i .e. 82 in total (1.4% of the spermatozoa in the sperm storage tubules and 0.001% of spermatozoa in the ejaculate). Female zebra finches that completed a natural breeding cycle with a mean of 12 copulations had 404 +/- 111 spermatozoa trapped on the perivitelline layer of all eggs of the clutch, and an estimated further 173 spermatozoa penetrated th e perivitelline layer. A smaller proportion of spermatozoa was trapped on the perivitelline layer of zebra finch eggs, than in chicken or tu rkey eggs.