Energy metabolism was examined in the spermatozoa of the sea urchins Arbacia lixula and Paracentrotus lividus, which belong to the orders Arbacioida and Echinoida respectively. P. lividus spermatozoa contained various phospholipids and cholesterol, and their endogenous triglyceride (TG) content was quite low. After dilution of dry sperm in artificial seawater, the level of phosphatidylcholine (PC) decreased rapidly, but other phospholipids remained at constant levels. In contrast to those of P. lividus, the spermatozoa of A. lixula contained TG as well as phospholipids and cholesterol. Following incubation of A. lixula spermatozoa in artificial seawater, TG decreased, but there were no concomitant changes in the levels of phospholipids. Trace amounts of glycogen were present in both species. High lipase activity was demonstrated in A. lixula spermatozoa, but in P. lividus spermatozoa lipase activity was low and phospholipase A2 activity was high. It is thus concluded that A. lixula spermatozoa obtain energy for swimming through oxidation of endogenous TG, whereas P. lividus spermatozoa use PC as a substrate for energy metabolism. This suggests that the system of energy metabolism in spermatozoa is different in the orders Arbacioida and Echinoida.

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In bullfrog (Rana catesbeiana) tadpoles, the lung begins to function at an advanced stage of metamorphosis. As a preliminary step for investigation of the mechanisms involved in lung maturation, pulmonary surfactant was prepared from tadpoles at advanced stages of metamorphosis and its biochemical properties were analyzed. Surfactant phospholipid analysis revealed that the major constituent was phosphatidylcholine (PC), as examined in the animals at late climax (stage 24). Other detectable phospholipids were phosphatidylethanolamine, phosphatidylserine, sphingomyelin, and phosphatidylglycerol, a marker lipid in mammalian surfactant. As in mammals, PC in the surfactant was rich in saturated fatty acids, about 50% of fatty acid moieties being palmitic acid. The content of surfactant PC in the lung increased moderately around mid-climax and markedly at the end of climax. The effect of antiserum against bullfrog prolactin (PRL) on the pulmonary surfactant was studied in climactic tadpoles. The content of surfactant PC in the lung of the antiserum-treated larvae was lower than that in the lung of the normal rabbit serum-injected larvae, whereas the content of PC in the whole lung did not differ between the antiserum-treated and control groups. The results suggest that synthesis of surfactant in the amphibian lung is enhanced as metamorphosis progresses and that PRL is involved in lung maturation.

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