Figure 1.

Effect of collagenase and acidified Tyrode's solution treatment on oolemma observed by DIC. a Collagenase treatment. b, c Acidified Tyrode's solution treatment. Collagenase treatment caused little or no damage to oolemma that have a smooth surface (a), while acidified Tyrode's solution treatment caused undesired significant damage to oolemma in various ways; one has a smooth surface (b), and the other has some damaged membrane that ruptured, leading to egg collapse (c). The dark area on right side of b and left side of c are the polar bodies that are out of focus. Bar 20 μm