ENERGY-METABOLISM OF SPERMATOZOA OF THE SAND-DOLLAR CLYPEASTER-JAPONICUS - THE ENDOGENOUS SUBSTRATE AND ULTRASTRUCTURAL CORRELATES

Energy metabolism in spermatozoa of the sand dollar-sea urchin Clypeas ter japonicus was examined. The spermatozoa contained triglyceride and cholesterol ester besides several kinds of phospholipids and choleste rol. Glycogen and glucose were present at extremely low levels. Follow ing incubation of spermatozoa in seawater, the triglyceride content de creased rapidly. Other lipids, however, remained at constant levels. H igh lipase activity was demonstrated in the spermatozoa. Also, [1-C-14 ]oleic acid was oxidized to (CO2)-C-14. Ultrastructural study showed t hat lipid globules were present at the bottom of the midpiece. After i ncubation in seawater, morphological changes in the lipid globules wer e observed and vacuoles of various sizes appeared near the lipid globu les. Thus, it is concluded that C. japonicus spermatozoa obtain energy through oxidation of fatty acid from triglyceride stored in the lipid globules at the midpieces.