Studies on the Respiration of Sea-Urchin Spermatozoa

Abstract

1. The effect of PCOCO2 on the respiration and motility of sea-urchin spermatozoa was studied on Anthocidaris crassispina. Some points were also corroborated on Hemicentrotus pulcherrimus, Pseudocentrotus depressus, Paracentrotus lividus and Sphaerechinus granularis. 2. It was found that any level of CO2 above 1%, both in oxygen and in air, inhibited the O2 uptake of spermatozoa suspended in sea water, measured polarographically with a vibrating platinum electrode. The inhibitory effect paralleled the PCOCO2 and was completely reversed by introducing oxygen or air. 3. pH variations between 8.50 and 6.75 had no influence on O2 uptake, when the pH was stabilized with 0.05 Mhistidine-HCl-NaOH. O2 uptake was, however, reduced to some extent outside this range, especially on the acid side. Although the increase in PCOCO2 is inevitably followed by a decrease in pH, the inhibitory effect of CO2 far exceeds that caused by the reduction in pH. 4. The O2 uptake rate was little affected by the addition of both bicarbonate and carbonate ions to the suspending medium, although the former had a slightly stimulating effect at certain concentrations. 5. In buffered sea water, CO2 had little influence on O2 uptake even at partial pressures as high as 10% which inhibited the bulk of O2 uptake in sea water. 6. Sperm motility was also inhibited by CO2. In this case, too, the inhibition paralleled the PCOMCOM2 and was completely reversible. The effect was more pronounced in air than in oxygen, and in dense sperm suspensions than in dilute ones. 7. These results suggest that gaseous CO2 is the factor responsible for the inhibitory effect. The possible role of CO2 in the dilution phenomena of sea-urchin spermatozoa is discussed.