PROBABLE SPERMATOZOAL DIPLOIDY IN THE SEMEN OF A GOLDEN RETRIEVER

The semen of a 3-year-old golden retriever was examined for breeding p urposes. When the morphology of the spermatozoa was analysed for the f irst time, 37% were observed to have giant heads. In most of the giant heads, a diadem defect was also found. The dog was successfully used for breeding. On re-examination, the percentage of giant heads was fou nd to be greater than before. The right testicle exhibited tissue soft ening. To determine the reason for the defect, an aspiration needle bi opsy was performed and ultrasound examination undertaken. In the biops y smears, both normal spermatozoa and spermatozoa with giant heads wer e found. On ultrasonography, the echogenicities of both testicles were the same, and normal. DNA flow cytometry was performed to determine t he DNA content of the spermatozoa. Two populations of sperm cells were detected, one having a median fluorescent intensity twice as high as that of normal spermatozoa, suggesting a diploid DNA content. Transmis sion electron microscopy (TEM) was performed to find out whether the a ltered intensity correlated with the ultrastructure of the spermatozoa . The nuclei of the sperm heads showed a normal chromatin condensation . Semen quality became worse over a period of 2 years, with 60% giant heads in the last sample. The process was considered to be progressive spermatogenic degeneration with diploidy. Relatives examined did not suggest any hereditary predisposition to the problem. The male was sti ll fertile at the time of the last sample collected and sired a litter of 10 healthy puppies.