Fig. 3From: The second highest chromosome count among vertebrates is observed in cultured sturgeon and is associated with genome plasticityComparison of normal fertilization, retention of the second polar body, and dispermic fertilization of a tetraploid female (4n) by spermatozoa of hexaploid male (6n). a Normal fertilization of diploid (2n) oocyte by triploid (3n) spermatozoon. b Retention of the second polar body in meiosis II results in tetraploid (4n) unreduced oocytes. If such an oocyte is fertilized by a triploid (3n) spermatozoon, it results in heptaploidy (4n♀ + 3n♂ = 7n), which is the ploidy level observed in the seven individuals under study. c Dispermic fertilization results in an octaploid (8n) zygote. If a diploid (2n) oocyte is fertilized by two triploid (3n) spermatozoa from a hexaploid male (6n), it will lead to octaploidy (2n♀ + 3n♂ + 3n♂ = 8n)Back to article page