Ultrastructure of pig tubal ova

Summary The unfertilized ova of the pig are characterized by the first polar body situated in the perivitelline space. The metaphase chromosomes of the ova are found free in a cortical area, predominantly inhabited by the spindle fibers. Mitochondria show morphological changes in the form of swelling of their matrices. Frequently, the membranes of the individual cristae mitochondriales meet each other, forming meeting points, at regular intervals. The endoplasmic reticulum increases in quantity when compared with that of the pig follicular oocytes (Norberg, 1972b). The Golgi complexes are sparse and scattered. Occasionally, remnants of the end bulbs of the corona radiata cell processes occur below the surface membrane of the ova.Usually, the sperm-penetrated ova contain the first and the second polar body within the perivitelline space. Intranuclear annulate lamellae are observed within the male and female pronucleoplasm, and of particular interest are extended linear structures in one of the pronuclei. These structures may be considered as precursor stage in the formation of the intranuclear annulate lamellae. The parapronuclear cytoplasm is rich in organelles, especially the cytoplasmic annulate lamellae. In contrast to the scarcity of Golgi complexes in the unfertilized ova, many newly formed Golgi vesicles and lamellae reappear in the pronuclear stage. The zona pellucida displays ultrastructural changes following sperm penetration of the ova.This work was supported by the Agricultural Research Council of Norway.