• A Gopalakrishna

      Articles written in Proceedings – Animal Sciences

    • Early development, implantation and amniogenesis in the Indian vampire bat,Megaderma lyra lyra (Geoffroy)

      A Gopalakrishna M S Khaparde

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      The embryo ofMegaderma lyra lyra enters the uterus as a morula. The blastocyst establishes contact with the uterine wall circumferentially at the level of implantation. The orientation of the embryonic mass at early stages is variable, but the flat embryonic disc at later stages is invariably mesometrially oriented. The preimplantation response of the uterus is markedly evident in the enormous expansion of the uterine glands and the hypertrophy of their cells. After the attachment of the blastocyst there is a rapid degeneration of the uterine glands and the cells of the endometrial stroma resulting in the formation of a thick zone of symplasma into which roots of the trophoblast enter. The maternal blood capillaries increase in number and their endothelial cells undergo hypertrophy. The amniotic cavity is formed by cavitation, but with the expansion of the embryonic disc the original roof of the amnion undergoes rupture and loss. The definitive amnion is formed by the development of folds from the margin of the embryonic disc.

    • Development of the foetal membranes and placentation in the Indian false vampire bat,Megaderma lyra lyra (Geoffroy)

      A Gopalakrishna M S Khaparde

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      The amnion expands to accommodate the growing foetus without undergoing any noticeable histological change. The yolk sac is large and forms an extensive chorio-vitelline placenta on the lateral sides of the uterus during early stages of gestation. However, due to the extension of the exocoelom and the expansion of the amniotic cavity the vascular splanchnopleure of the yolk sac is separated from the placenta and is invaginated towards the abembryonic trilaminar omphalopleure. The endodermal cells of the yolk sac hypertrophy as the yolk-sac wall gets vascularized, and the mesodermal cells enlarge only during the final stages of pregnancy. The allantoic vesicle, which is large during early stages of gestation, becomes progressively reduced and is finally lost during the final stages of pregnancy. The placenta, which is extensive during early stages, becomes restricted to a discoidal structure on the mesometrial side of the uterus. The definitive placenta is labyrinthine and vasomonochorial. Numerous free chorionic villi, which come into direct contact with the decidua at the margin of the placental disc, constitutes an accessory syndesmochorial placenta.

    • Morphogenesis of the foetal membranes and placentation in the bat,Miniopterus schreibersii fuliginosus (hodgson)

      G C Chari A Gopalakrishna

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      The development of foetal membranes and the changes in the structure of the placenta in the batMiniopterus schreibersii fuliginosus is described. The study reveals thatM. schreibersii fuliginosus exhibit developmental characters not matched by any other mammal let alone any other bat.

    • Morphogenesis of the foetal membranes and placentation in the Indian molossid bat,Chaerephon plicata (Buchanan)

      A Gopalakrishna Y D Pendharkar N Badwaik

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      InChaerephon plicata the definitive amnion is formed by the development of folds. The yolk-sac splanchnopleure undergoes progressive collapse and folding until it ultimately remains as a free gland-like structure with hypertrophied endodermal and mesodermal cells. It acts as an active haemophagous organ after limb-bud stage. An extensive chorio-vitelline placenta, which is formed during early gestation is progressively abolished and replaced by the chorio-allantoic placenta. Two kinds of chorio-allantoic placenta are formed—a diffuse endotheliochorial placenta, which persists until about midpregnancy, and a definitive discoid placenta which is mesometrically located, labyrinthine and haemomonochorial.

    • Vascularisation of the placenta in some bats

      A Gopalakrishna N Badwaik

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      Vascularisation of the placenta of several species of bats representing 8 families is reported. Maternal vascularisation in all these bats is effected by a few large vessels which pass through the entire thickness of the placenta and give rise to numerous radial branches on reaching the foetal surface of the placenta. Maternal blood is returned through placental tubules which empty into large venous channels at the utero-placental junction. Foetal vascularisation is brought about by two allantoic arteries which capillarise over the placental tubules, and a large allantoic vein. In the exchange areas there is mostly crosscurrent circulation of the maternal and foetal bloods. Only in emballonurid bats is there an haematoma from which maternal blood is not drained back but is absorbed by cells of the trophoblast of chorionic villi.

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