SEM observations on polar body elimination and changes of the oocyte surface during egg maturation in the newt Triturus alpestris (Amphibia, Urodela).

We have studied the surface of the animal half of ovulated newt eggs recovered from different portions of the oviduct. The germinative area, about 40 μm diameter, is localized in the region of the whitish polar spot, about 450 μm diameter. The structural changes in the germinative area are connected with the formation and extrusion of the first and second polar bodies. Of the two types of oviductal eggs observed, those covered with microvilli (type 1) were found only in the ostial portions of the oviduct, whilst those covered with microfolds (type 11) were found more distally. The structural difference between these two types may be related to the known reduction in surface area of the cell membrane during oocyte maturation.