On the magnesium content in sea urchin eggs and its changes accompanying fertilization

Summary The content of total and bound magnesium of the eggs ofPseudocentrotus depressus andHemicentrotus pulcherrimus was estimated by atomic absorption spectrophotometry. The amount of total magnesium was almost equal (0.128 gmg/g PO₄) in both species and did not change upon fertilization. Bound magnesium decreased in fifteen minutes after fertilization and recovered the original value in further fifteen minutes. The role of magnesium in the fertilization process was discussed with the presence of the experimental results.