Search Results

Summary. Only a very few spermatozoa were found in the ampulla of the oviduct just after ovulation. The spermatozoa lost both the acrosome cap and the equatorial segment while passing between the cumulus cells surrounding an ampullar egg; many such spermatozoa were found in the perivitelline space. One spermatozoon was seen in contact with the plasma membrane of the ovum in the metaphase of the second meiotic division. Excess spermatozoa in the perivitelline space were phagocytosed by pseudopodial protrusions from the blastomere surface.

Summary. In the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus, ovulation occurred spontaneously with the disappearance of the granulosa layer and germinal epithelium at the apex of the stigma which was formed simultaneously with expulsion of the first polar body, and with the subsequent bleeding from the capillary lumina of the theca interna. After ovulation the rupture point was plugged by luteinizing granulosa cells and overgrown by newly regenerated cells of the tunica albuginea and germinal epithelium.

Summary. Live spermatozoa were first stored in the colliculus tubaricus of the uterotubal junction (UTJ) on both sides, Spermatozoa then ascended to the caudal isthmus just before ovulation. Spermatozoa with intact acrosomes in the caudal isthmus, which had their heads orientated towards the cephalic isthmus, were seen amongst groups of epithelial cilia in parallel to the epithelium; on the other hand, acrosome-less spermatozoa that were not attached to the epithelium were orientated irregularly in the lumen. A few acrosome-intact spermatozoa were found in the left ampulla at the time of ovulation of the single egg on the left side. Most of the spermatozoa failed to reach or survive in the ampulla of the right oviduct and leucocytic phagocytosis was restricted to this side.

Summary. In the Japanese long-fingered bat, Miniopterus schreibersii fuliginosus, spermatozoa in contact with the microvilli of non-ciliated cells in folds in the uterotubal junction appeared normal, while spermatozoa remaining in the uterus degenerated and were engulfed by a massive invasion of polymorphonuclear leucocytes. No leucocytes were seen in the uterotubal junction area. It is suggested that the spermatozoa in this area are being stored, probably until ovulation occurs.

Summary. The placentae of the Japanese long-fingered bat were characterized by their morphological and functional transition from the main placenta to the accessory placentae. The main placenta transformed from an endotheliodichorial to a haemodichorial (one layer of syncytiotrophoblast and one layer of cytotrophoblast cells) condition. Degeneration of the main placenta was accompanied by development of two accessory placentae. These developed on both sides (fetal side) of the main placenta, and subsequently converted from a haemodichorial (two layers of cytotrophoblast cells) to a haemomonochorial condition.

Summary. Embryonic development in Japanese long-fingered bats proceeded very slowly during and after the delayed implantation period (mid-October to mid-December). The primitive amniotic cavity and endoderm were formed before implantation. At the preimplantation stage (before hibernation) the corpus luteum cells appeared active, but became less active at the implantation stage (in hibernation). Activity was again apparent at the early placentation stage (after arousal).

Summary. In the Japanese long-fingered bat, when compared with the baseline values during non-pregnancy in the autumn, plasma progesterone concentrations were not significantly elevated during the delayed implantation stage that begins before the bats enter hibernation. However, progesterone concentrations were significantly lower during the delayed development stage that occurs during hibernation and rose significantly during the rapid embryogenesis that occurs after arousal from hibernation in the spring. Changes in the corpus luteum volume corresponded closely with those of plasma progesterone values. Maintenance of gravid females at 25°C for 2 weeks in winter resulted in significant increases in the plasma progesterone concentration and the corpus luteum volume.

Summary. Gravid female Japanese long-fingered bats were kept in captivity without hibernation at elevated temperatures (23–25°C) in winter. The embryonic growth rate was accelerated and consequently parturition was advanced by a period equivalent to that of exclusion from hibernation as compared with that in the wild population. The corpus luteum became active, as indicated by an increase in the 'light' lutein cells in an experimental bat pregnant with a 15-mm embryo, but was less active (more 'dark' cells) in 2 hibernating control bats with an implanting blastocyst.

Summary. After the mating season of the Japanese greater horseshoe bat in mid- or late October, only the right ovary maintained a single Graafian follicle throughout hibernation until early April. During this time the ovum was in prophase of meiosis I (resting stage) with many large lipid droplets as a nutrient source. In synchrony with stigma formation, there was resumption of meiotic activity, separation of the cumulus oophorus from the granulosa layer and dispersion of the follicle cells just before ovulation in spring. The block to polyspermy seemed to reside in the zona pellucida, because no spermatozoa could be detected in the perivitelline space of the 6 fertilized ova examined, although a second spermatozoon was recognized in the zona pellucida of 3 ova.

Summary. The vaginal plug of the Japanese greater horseshoe bat is composed of an outer, thick, hard and homogeneous layer originating from the stratum disjunctum of the vaginal mucosa and a thin, soft and opaque central core containing accidentally trapped dead spermatozoa. The vaginal plug appeared to be expelled just before or after ovulation in spring. Immediately after copulation in autumn, uterine spermatozoa were dead but few leucocytes were present. As time passes after copulation, however, the infiltration of leucocytes into the uterus increased gradually, and extensive leucocytic phagocytosis of dead spermatozoa occurred during hibernation.