The counting and sizing of spermatozoa from ten animal species using a Coulter counter

Accurately calibrated Coulter Counters, Models ZB Industrial and F, were used to count and size spermatozoa before and after Zaponin treatment which lyses accompanying debris, droplets and peripheral sperm cytoplasm. Sperm specimens from the cauda epididymis of the rabbit, Guinea pig, hamster, rat and mouse were without accompanying particles and could be sized without Zaponin treatment. The large acrosome cap of the guinea pig swelled rapidly when the spermatozoa were released into an isotonic solution and measurement was only possible after equilibrium had been reached. Zaponin treatment completely dissolved rat and hamster spermatozoa within a few seconds and about 50% of the mouse spermatozoa. Spermatozoa form the cauda epididymis of the bull were accompanied by some unspecific debris which made size determination without Zaponin treatment difficult. A separate population of cytoplasmic droplets was not present and the amount of accompanying cytoplasm, as shown by its removal with Zaponin, was the least for the species examined. The size of spermatozoa in ejaculated specimens from the dog varied considerably according to whether the cytoplasmis droplet was still present, but after Zaponin treatment all specimens were about the same size. Ejaculated specimens from the European wild boar contained a separate population of small droplets which were sufficiently different in size from the spermatozoa to allow separate counting and sizing without Zaponin treatment. Ejaculated specimens from the Rhesus monkey required incubation to release the spermatozoa from the clot before they could be counted and sized. Their size tended to vary slightly according to the length of incubation. Ejaculated specimens from the rabbit and from man were so heavily contaminated with debris that counting and sizing was not possible without Zaponin treatment. The relationship between the amount of debris and the numbers of spermatozoa was extremely variable. The debris in human specimens was separated from the spermatozoa by downward fractionation of the motile spermatozoa into increasing concentrations of bovine serum albumin, so allowing measurement of untreated spermatozoa for the first time. The sperm size distribution curves for all the ten species examined, both before and after Zaponin treatment, were positively skewed. The peaks were broader and flatter when Zaponin was not used. Sperm sizes, in terms of total volume and of the diameter of a sphere of that volume, are given for all the species at both the mode and the mean of the size distribution curves. After Zaponin treatment the mean size was between a volume of 15 and 50 mum3 or an equivalent spherical diameter of 3-5 mum. Before Zaponin treatment all the sperm types were greater than 20% larger by volume and the mean volume was between 25 and 190 mum3.