Keywords: sperm, abnormalities, spermatology, canine, dog
These spermatozoa were selected from a smear stained with a standard eosin-nigrosin morphology stain. The sample is from a three-year-old Samoyed dog that had sired one litter. Semen was being collected and processed for cooling and shipping.
The percentage of progressive motile sperm was approximately 70% and the morphology was excellent, with greater than 90% normal spermatozoa under phase contrast examination. The stained preparation revealed similar excellent the morphology, therefore some searching was necessary to find a sample of abnormal spermatozoa. In this image some of the spermatozoa would be considered normal at first glance; perhaps numbers is 2, 3, 7, 9, 11 and 12. However, closer examination (the image can be enlarged by clicking on it for this purpose) shows that those spermatozoa, apart from number 3, all have abaxial attachments to their heads. The significance of this in dogs is unknown but it does not appear to be a serious defect in other animals, being especially common in boars.
It is clear that the acrosomes of spermatozoa numbers 1 and 5 were expanded and perhaps on the verge of detatching. This is a relatively common defect in canine semen samples and in view of the importance of the acrosome in fertilization, must be associated with infertility. In some semen samples, loose acrosomes can be seen floating by themselves much as loose heads (number 17) are. Spermatozoa numbers 4, 10, 13, 14, 15 and 16 show various forms of bent tails. In one case the midpiece was involved (13) but in the other sperm (4, 14 and 15) the bent tail appears to involve the main piece only even if it is curved back and adherent to the midpiece. In some cases, the cell membrane may fuse between two sections of a bent tail; an example being spermatozoa number 4. Obviously, spermatozoa with bent tails are associated with infertility. However some caution is advised when diagnosing bent tails because some spermatozoa will develop bent tails in their agonal stages of dying; a normal tail can be seen to flip up and adhere to the midpiece as a spermatozoan dies. Spermatozoa numbers 5 and 6, show the midpiece defects that are probably expanded mitochondrial sheaths. In one case (number 6) the defect is proximal and any other (number 5) it is distally situated on the midpiece. It is possible that the defect thought to be an expanded midpiece in spermatozoa number 5, could indeed be a distal droplet (a maturational defect) but it would only be possible to make such a statement if the spermatozoan was examined under transmission electron microscopy. The mitochondrial sheaths are responsible for energy metabolism; essential for the motility of spermatozoa. Therefore defects in the mitochondrial sheaths are associated with potential infertility.
It is possible that spermatoazoa 8, 9 and 14 have cavitation defects in their heads ( the small white dots visible under their acrosomes). The significance of these defects is unknown.
Interestingly the end pieces of these spermatozoa i.e. the thin filament at the end of the tail of a spermatozoan were often visible in the sample. That is unusual but maybe it testament to the excellent optics of the Olympus BX51 microscope used for these images.
