ABSTRACT
Sea-urchin spermatozoa (Echinus esculentus) contain 4·14 mg. phospholipid per 1010 spermatozoa (arithmetic mean of five replicated experiments, standard error 0·06). This amount of phospholipid is about 5·5 % of the dry weight of a seaurchin spermatozoon.
The seminal plasma contains very small quantities of phospholipid, about 20 mg./100 ml., less than one-thirtieth the content of fresh semen.
When sea-urchin semen was diluted 1:20 with sea water and the spermatozoa incubated aerobically for some 7 hr. at 20° C., phospholipid disappeared. The average disappearance per 1010 spermatozoa was 19·0% (S.E. 2·4), while the corresponding oxygen uptake of the same sperm suspensions during the same time was 1·450 ml. (S.E. o·118). The oxidation of glycogen or glycogen-like material was found to be entirely insufficient to account for the observed oxygen consumption.
Assuming that the combustion of 1 mg. phospholipid requires 1·6 ml. oxygen, the ratio of the theoretical oxygen uptake (associated with the observed disappearance of phospholipid) to the observed oxygen uptake was 0·86 (S.E. 0·04).
It is concluded that the oxidative breakdown of phospholipid, located in the middle-piece, is the principal source of the energy required for movement.
We are much obliged to Dr J. R. G. Bradfield, Cavendish Laboratory and Department of Zoology, Cambridge, for taking electron micrographs of these spermatozoa for us.
