After defining the best fertilization conditions, new experiments were conducted to monitor meiotic development and to determine the period of the release of the polar bodies
and first mitosis in experimental units of 5 L.
One attachment is located anterior to the chondrocranium at the anterior trabeculae, another attachment is at the polar bodies
, and the third is a posterior attachment at the otic capsule (containing the inner ear).
Two polar bodies
are formed as an oocyte reaches maturity.
The cleavage furrow was colocated with the position of the extruded polar bodies
at the animal pole.
oocytes extruded their first polar bodies
without migration of the spindle (Verlhac et al.
Division of polar bodies
induced by their enlargement in the starfish Asterina pectinifera.
The European Society of Human Reproduction and Embryology (ESHRE) PGS Task Force has now shown, in its groundbreaking proof of principle study, that screening of polar bodies
(small cells that are the by-product of egg development), is a reliable method to analyse the chromosomal status of an egg.
The fertilized egg extrudes the first and second polar bodies
at 8-10 min, and then the zygote begins cleavage at 15-20 min.
Each cleavage furrow is numbered in the order of its occurrence, and the polar bodies
(pb and arrow) are visible resting in the first cleavage furrow.