Energy metabolism of sea urchin spermatozoa: the endogenous substrate and ultrastructural correlates

In higher animals, spermatozoa have the biologically important roles of egg activation and transmission of the male genetic message to offspring. For this purpose, spermatozoa must swim towards the egg. Sea urchin spermatozoa which are stored in the testis are immotile and their respiration is low ( Gray 1928 ; Rothschild 1956 ). Upon spawning in seawater, these spermatozoa begin flagellar movement and the respiration is activated. Since the flagellar movement in spermatozoa occurs partly through reactions catalyzed by dynein ATPase ( Gibbons & Gibbons 1972 , Christen et al. 1982 , 1983a, Evans & Gibbons 1986 ), energy metabolism for production of ATP by mitochondrial respiration is indispensable for swimming. In this review, we describe energy metabolism in sea urchin spermatozoa.