ENDOGENOUS SUBSTRATES FOR ENERGY-METABOLISM IN SPERMATOZOA OF THE SEA-URCHINS ARBACIA-LIXULA AND PARACENTROTUS-LIVIDUS

Energy metabolism was examined in the spermatozoa of the sea urchins A rbacia lixula and Paracentrotus lividus, which belong to the orders Ar bacioida and Echinoida respectively. P. lividus spermatozoa contained various phospholipids and cholesterol, and their endogenous triglyceri de (TG) content was quite low. After dilution of dry sperm in artifici al seawater, the level of phosphatidylcholine (PC) decreased rapidly, but other phospholipids remained at constant levels. In contrast to th ose of P. lividus, the spermatozoa of A. lixula contained TG as well a s phospholipids and cholesterol. Following incubation of A. lixula spe rmatozoa in artificial seawater, TG decreased, but there were no conco mitant changes in the levels of phospholipids. Trace amounts of glycog en were present in both species. High lipase activity was demonstrated in A. lixula spermatozoa, but in P. lividus spermatozoa lipase activi ty was low and phospholipase A(2) activity was high. It is thus conclu ded that A. lixula spermatozoa obtain energy for swimming through oxid ation of endogenous TG, whereas P. lividus spermatozoa use PC as a sub strate for energy metabolism. This suggests that the system of energy metabolism in spermatozoa is different in the orders Arbacioida and Ec hinoida.