Preimplantation embryonic development in a tropical vespertillionid bat


Pranab Lal Pakrasi, Embryo Physiology Laboratory, Center of Advanced Study, Department of Zoology, Banaras Hindu University, Varanasi 221005, India. Fax: +91 0542 2368174


Early embryonic development and implantation were studied in one of the Indian tropical bat Scotophilus heathi. This species is selected from its previous reports for an alternate animal model to study the reproduction in mammals. This bat is monoestrus. It also exhibits differential growth of embryos and generally one implantation per uterine horn. Embryo development was studied with dated pregnant females bred in captivity. Scotophilus heathi is an induced ovulator requiring several matings for ovulation to occur. In captivity, generally, it ovulates a single ovum after the third mating in captivity. The second ovulation occurs either at the fourth or fifth matings in the case when first ovulation occurs at the third mating. In our experiment, 70% of the bat ovulated both the ova simultaneously either at the fourth or fifth mating. The females that showed differential ovulation also showed differential embryonic development and differential implantation. The embryos could not begin compaction during cleavage and went to a state of block for about 8–10 days at the 6–8-cell stage. This block was found to be related to the formation of corpora lutea. Culmination of block coincides with the presence of progesterone in serum. Then, the developmental block is removed and embryos resume development. The total preimplantation period of development takes 20–22 days including the block period. This study reports that bat embryonic development can be studied like in other laboratory animals. It may also provide another model to study developmental block.