Morphological and biochemical changes in sperm at fertilization

Morphological and biochemical changes in sperm at fertilization under physiological conditions were examined. After fixation with glutaraldehyde containing Janus Green B, the sperm were well preserved not only on the egg surface but also in the jelly layer (Kato, ‘87). Using this method, two different morphological changes in sperm were observed. 1. In the jelly layer, the sea urchin, Pseudocentrotus deprressus were acrosome-reacted. 2. Mitochondria of sperm which adhered on the egg surface became spherical. In swimming sperm, the ATP content was low but ADP level was kept high. On the contrary, in quiescent sperm which were interacted with fixed eggs, the ADP level was markedly low and the ATP content was high. Such quiescent sperm had very low respiratory rate but recovered by the addition of uncoupler, DNP. The electron micrographs showed that the matrix of mitochondria was the condensed conformation in active sperm and the orthodox conformation in reacted one. These results suggest that the energy state of sperm is altered from state 3 to state 4 after the morphological changes in sperm at fertilization.