PARENT SESSION
Epididymis and Sperm Maturation

ANALYSIS OF CHARACTERISTICS AND CRYOSURVIVAL OF SPERM FROM THE CAPUT, CORPUS AND CAUDA EPIDIDYMIS OF THE DOMESTIC DOG.

Anderson, Autumn¹, Amodeo, Dianne¹, Wetsman, Irene¹, Olson, Mary¹, Durrant, Barbara¹, ¹

ABSTRACT- Post-mortem epididymal sperm extraction represents an important source of germplasm from endangered species, but the development of sperm cryopreservation protocols for rare animals is best accomplished using a more plentiful model species. Previous work in our laboratory has shown that the domestic dog is an excellent model for many carnivore species. This study compared the quality and quantity of spermatozoa from the caput, corpus, and cauda epididymis of sexually mature dogs. Each of the three epididymal regions was isolated and minced into TEST-Yolk buffer. Initial motility score (IMS, motility x speed of progression²), plasma membrane integrity (IL, initial live determined by eosin-nigrosin staining), concentration and morphological abnormalities were recorded for each region. Sperm from the cauda exhibited significantly (p<.05) higher IMS and IL than caput and corpus sperm. Region significantly affected concentration (p=.003) with progressively higher counts from caput through corpus to cauda. The predominant abnormalities in each of the three regions were immature sperm and detached heads. Transit through the epididymis resulted in a decline in immature sperm (p<.001) and a tendency (p=.09) for an increase in detached heads. After initial analysis sperm was cooled to 4°C over 30 min, and glycerolated TEST-Yolk buffer was added for a final concentration of 4% glycerol. Sperm was frozen in vials over LN₂ vapor and stored for a minimum of 10 days LN₂. Vials were thawed for one minute in a 37°C water bath and assessed for motility score and plasma membrane integrity. Post-thaw %IMS and %IL were significantly (p<.05) higher in cauda epididymal sperm compared to sperm collected from the caput or corpus. These data indicate that extraction from the cauda epididymis yields the highest quality and quantity of fresh sperm, and that sperm from this region exhibits the greatest cryosurvival.

KEY WORDS: epididymis, dog, cryopreservation, morphology