CHANGE IN THE GLYCOGEN CONTENT OF SEA URCHIN EGGS DURING EARLY DEVELOPMENT

During development of eggs of the sea urchins, Pseudocenrotus depressus and Anthocidaris crassispina, the glycogen level is maintained from the time of fertilization to the swimming blastula stage and then decreases rapidly in the early gastrula stage. During development of eggs of Clypeaster japonicus. Hemicentrotus pulcherrimus and Mespilia globulus the glycogen content decreases slowly from the time of fertilization to the mesenchyme blastula stage, and then more rapidly during gastrulation. The amounts of glycogen mobilized in the embryos from the time of fertilization to the morula stage correspond to 67% of the amount of O2 consumed in Mespilia eggs, 62% in Clypeaster eggs, 30% in Hemicentrotus eggs and 0-4% in Anthocidaris and Pseudocentrotus eggs. The main energy source in early development seems to differ in different species. When eggs and embryos were incubated with [14 C]glucose for 10min, considarable 14 C-radioactivity accumulated in the glycogen fraction. The rate of [14 C]glucose incorporation into glycogen increased gradually during the first 6 hr after fertilization (up to the morula stage), decreases during the next 4 hr (up to the early blastula stage), and then increased again.