Motility of undiluted bull epididymal spermatozoa collected by micropuncture

Motility of whole undiluted semen collected from different regions of the bull epididymis by micropuncture was determined by examining a droplet under paraffin oil. Bull caudal spermatozoa showed vigorous motility in undiluted semen. This motility was less in samples collected from nearer the testis: samples from the distal caput showed weak but detectable motility while those from the proximal and mid-caput were completely quiescent. Motility of spermatozoa from the distal caput and the proximal corpus was markedly increased after incubation at 34 or 37 degrees C for 1 h, but was depressed by incubation at 25 degrees C. Similar but smaller effects were observed with spermatozoa collected from the mid-corpus and the mid-cauda, except that motility of spermatozoa from the mid-corpus was reduced after incubation for 1 h at 37 degrees C. The inhibitory effect of low temperature was completely reversible. Incubation of caudal spermatozoa under anaerobic conditions produced partial and reversible inhibition of sperm motility. The results suggested that bull epididymal spermatozoa may not be completely quiescent in their native environment as previously assumed.