How does sperm meet egg?--in a marsupial.

摘要: Australian marsupials exhibit a wide range of variation in sperm head morphology, and thickness the zona pellucida around oocyte, suggesting interspecfic differences processes sperm-egg interaction. The observations described here are largely based on dasyurid Sminthopsis crassicaudata. They show that oestrous females, after mating, coagulum forms lateral vaginae and, within an hour insemination, numerous spermatozoa congregate isthmus oviduct which vanguard population undergoes transformation with rotating its axis tail to form T-shape. Once oocytes released, few migrate higher reaches where sperm-zona binding occurs by way plasmalemma over acrosomal region. acrosome reaction takes place as egg rotates, spermatozoon becomes parallel head. A small region sometimes appears remain intact at this time because partly acrosomes have been found matrix. In some these, electron-dense bridges between part inner outer membranes may act stabilizing structures, were also seen. matrix is tightly packed penetrating spermatozoon, but close less more filamentous. incorporated into egg, lacks cell membrane vesicles may, least part, be remnants membrane. How generally applicable these other remains determined.