A spermatozoal midpiece abnormality associated with infertility in a Llasa Apso dog

The semen of a 9‐year‐old Llasa Apso dog with a recent history of infertility was examined by light and electron microscopy. The presenting sperm abnormality was a high percentage (87 per cent) of cells with proximal cytoplasmic droplets. With the higher resolution of differential interference contrast microscopy and with transmission electron microscopy (TEM) it was apparent that not all of the midpiece abnormalities had the appearance of typical cytoplasmic droplets. Furthermore, by TEM both axonemal and mitochondrial defects were readily demonstrated, often with evidence of degenerative mitochondria in cytoplasmic swellings at other levels of the midpiece. These severe abnormalities were apparent only by TEM of thin sections, although scanning EM was useful in identifying abnormal midpiece outlines. It is suggested that the failure of droplet migration and the midpiece ultrastructural defects were linked to a common fault in spermateliosis.