Degeneration of Respiratory System in Sea Urchin Spermatozoa during Incubation in Seawater for Long Duration

Abstract Motility and respiration were examined in spermatozoa of the sea urchin Hemicentrotus pulcherrimus after dilution and incubation in seawater at pH 8.2 at 20°C. Almost all spermatozoa were motile during 12 hr of incubation, but their respiratory rate decreased gradually. The acrosome reaction was also induced by egg jelly solution during 12 hr of incubation in seawater. However, the ratio of spontaneous acrosome reacted spermatozoa was quite low during the same period. An intracellular pH (pHi) of spermatozoa was about 7.5 just after dilution in seawater and was almost constant during 12 hr of incubation. Upon dilution and incubation in seawater, activity of NADH-cytochrome c reductase decreased in propotion to the decrease in the respiration in spermatozoa, whereas cytochrome c oxidase activity was hardly changed. These suggest that the degeneration of respiratory system during 12 hr of incubation in seawater is due to the decrease in the NADH-cytochrome c reductase activity. In energy production...