The Physiology of Sea-urchin Spermatozoa Action of Versene

A description of the physiology of sea-urchin spermatozoa requires, among other things, an explanation of two special characteristics which these spermatozoa possess. First, immediately after dilution, the Og uptake per spermatozoon is higher in a dilute than in a dense suspension. Secondly, the decline in sperm motility and fertilizing capacity is more rapid in a dilute than in a dense suspension. The first of these characteristics can be reversed by diethyldithiocarbamate (Rothschild, 1950) and altered by copper ions (Rothschild & Tuft, 1950), while the second can be profoundly influenced by amino-acids (Tyler & Atkinson, 1950) and metal-chelating agents, including diethyldithiocarbamate (Tyler, 1953). Up till now there has been a tendency for these phenomena to be studied separately and on different species of sea-urchin spermatozoa. It was therefore decided to examine the Dilution Effect as a whole, using the spermatozoa of Echinus esculentus. We had both independently come to the conclusion that the Dilution Effect might be explained by the presence of trace elements, in particular copper, in the sea water. We therefore decided to examine the effect of the well-known chelating agent versene on the metabolism, motility and fertilizing capacity of these spermatozoa. This reagent was selected because there is some evidence that it is biologically innocuous (Hutner, Provasoli, Schatz & Haskins, 1950), while diethyldithiocarbamate, apart from being oxidized by cytochrome to tetraethyldithiocarbamyl disulphide, which itself may be an inhibitor, could exert a narcotic action, though there is evidence against this possibility (Rothschild, 1950). The study of mammalian spermatozoa is sometimes facilitated by 'washing' the semen before the experiment, which involves repeated centrifugation and replacement of the seminal plasma by solutions of known composition. Up till now this procedure has proved to be difficult to apply to sea-urchin semen which, by virtue of its high sperm density, is far more viscous than bull or ram semen. Because, however, of the possibility that sea-urchin seminal plasma might exert a chelating effect on trace elements in the sea water, we have re-examined the feasibility of centrifugation and washing, and the possibility that dilution of the seminal plasma may be responsible for the Dilution Effect.