Comparative Electron and Light Microscopy of Early Spermatids during Mammalian Spermiogenesis

The aim of the study was to compare the electron microscopic and microscopic characteristics of the first two phases of spermiogenesis in seven mammalian species. Material and methods. For electron microscopy, testicular specimens were fixed in 2.5% glutaraldehyde and 1% osmium fixative. Sections were prepared on BS-490 and LKB-4800 ultramicrotomes. Sections were contrasted with uranyl acetate and lead citrate and examined under a Tesla BS-500 electron microscope. Results. During the first Golgi phase, the Golgi apparatus forms an acrosomal vesicle and small granules. During the second cap phase, the small granules in the acrosomal vesicle combine to form a single large granule. The acrosomal vesicle and acrosomal granule spread over the nucleus, forming a cap. In northern fur seals, silver foxes, and minks, indentations in the spermatid nuclei were found at the location of the acrosomal vesicle. In sheep, sea otters, and beavers, indentations in the spermatid nuclei at the vesicle attachment site are absent. Conclusion. During the Golgi phase, the acrosomal vesicle and acrosomal granule form. During the cap phase, the acrosomal structure spreads over the apical surface of the nucleus, forming a cap over the nucleus. In the northern fur seal, fox, and mink, the acrosomal vesicle forms a deep depression in the spermatid nucleus, which is not found in the ram, beaver, and sea otter.

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