94 CHARLES TERNER 



hardly oxidize it at all. Of the two species of fish shown here, the 

 sucker produced spermatozoa of good motility, whereas the sper- 

 matozoa of the trout (brown and rainbow trout) were of poor mo- 

 tility, and the metabolic rates were much lower, although the pat- 

 tern is the same. 



The question whether human spermatozoa have a respiratory me- 

 tabolism has long been in doubt. It should be obvious from the data 

 why the oxygen consumption of isolated human spermatozoa has 

 perhaps never really been measured. Fortunately the sucker is re- 

 lated to man at least in the rate of substrate oxidation by spermatozoa. 

 If it is assumed that human spermatozoa have an endogenous respi- 

 ration as high as sucker sperm (which is unlikely), the oxygen uptake 

 of human sperm could not exceed 100 /J/10 10 spermatozoa/ hr. This 

 gives a maximum Z „ of ca. —1, that is, the oxygen uptake would be 

 1 ^tl/10 8 spermatozoa and probably much less than that. Since 10 s 

 spermatozoa is the average content of 1 ml of human semen, not 

 much can be expected from manometric measurements even using 

 micro-Warburg vessels. 



Another question regarding the metabolism of human spermatozoa 

 is whether their oxidative capacity is not so low that it may be dis- 

 missed as insignificant in comparison with the glycolytic system. Here 

 comparative studies may be useful. Sucker spermatozoa oxidize py- 

 ruvate at a rate similar to that of human spermatozoa and utilize 

 hardly any glucose. In fish spermatozoa, respiration has long been 

 known to be of far greater importance for the support of motility 

 than glycolysis (see Mann, 1954), and our isotope experiments confirm 

 that glycolysis is relatively slow. If oxidations at this "low" rate are 

 adequate to sustain fish sperm, they may also be useful to human 

 spermatozoa. The point that is made is simply this: if the supply of 

 fish sperm were as scanty in volume and sperm density as the single 

 human ejaculates on which manometric measurements have so far 

 been conducted, the conclusion might well be that fish spermatozoa 

 lack both the glycolytic and the oxidative mechanisms of energy 

 production. It is interesting to speculate what other mechanisms 

 imagination might have led us to propose as an alternative. 



It seems odd that man is closer to fish than to the bull as far as 

 the rate of sperm metabolism is concerned. The spermatozoa of mam- 

 mals, on the other hand, have in common the possession of a power- 



