Electron microscopy of the seminiferous epithelium in the triploid (ZZZ and ZZW) fowl, Gallus domesticus
Lin, M.; Thorne, M.H.; Martin, I.C.; Sheldon, B.L.; Jones, R.C.
Journal of Anatomy 186: 563-576
1995
ISSN/ISBN: 0021-8782 PMID: 7559129 Document Number: 443414
The ultrastructure of cells of the seminiferous epithelium was studied in both triploid ZZZ and ZZW fowls, especially cytological aberrations influencing the development of morphologically abnormal spermatids and spermatozoa. Mitotic divisions in triploid fowls were similar to those in diploid fowls, but meiosis in ZZZ and ZZW fowls was abnormal and many defective gametes were produced. The majority of spermatids had structural abnormalities and this was attributed to aneuploidy expected from meiotic chromosome pairing in a triploid. Some spermatids to possessed an irregularly shaped head, 2 centriolar complexes, 2 acrosomes and 2 tails and this type differentiated into large-headed spermatozoa. Such spermatids and spermatozoa were suggested to be near diploid due to their large nuclear size and 2 sets of organelles. Other spermatids, with only 1 centriolar complex, 1 acrosome and 1 tail, were suggested to be near haploid. Differentiation of these spermatids was similar to the process in diploid fowls except that there was a high percentage of abnormally shaped heads. The fact that morphologically normal spermatozoa were rare was consistent with the expectation that very few spermatozoa would be exactly haploid. In both ZZZ and ZZW triploid fowls, triple pairing of chromosomes was observed in synaptonemal complexes (SC) during meiosis and recombination nodules were distributed at random in the central regions of the triple pairing SC. In ZZW fowls, gamete formation was more severely affected than in ZZZ fowls and it was suggested that many of the degenerative changes occurring in ZZW fowls could be attributed to spermatids that possessed a W sex chromosome, since normal male fowls are the homogametic sex (ZZ) and normal spermatids and spermatozoa contain only a Z sex chromosome.