Bioscientifica Proceedings

The objective of this study was to investigate the precocious sexual maturation in stoat females. We confirmed oestrus and successful mating in newborn stoats; and documented ovulation, preimplantation embryo development, embryonic diapause and implantation during first nine months of life. A total of 100 embryos at different stages of development were flushed from the oviducts and uterine horns obtained from female stoats (Mustela erminea) between day 26 and day 251 after birth. At same time points, the ovaries were fixed, sectioned and analysed for the presence of follicles and corpora lutea.

Newborn stoat females entered oestrus during the first month of their life, i.e. in May-June in Northern hemisphere, and may stay in oestrus the whole summer until impregnated by an adult male. When mated, these females ovulated 3-4 days later. Embryos arrived in the uterus 11-12 days post coitum, slowly expanded and persisted as diapausing blastocysts until implantation 8-9 months later. We described the phenomenon of obligate delayed implantation in juvenile stoat females including timing of preimplantation embryo development and concluded that the stoat represents an unparalleled model for studying precocious sexual maturation and delayed implantation.

© Third International Symposium on Embryonic Diapause