Fertilization in the sea urchin, Strongylocentrotus purpuratus is blocked by fluorescein dyes

Abstract

Fertilization in gametes of the sea urchin Strongylocentrotus purpuratus was reversibly inhibited by several analogs of the anionic dye fluorescein. The dyes acted very rapidly and were effective when added before or several seconds after insemination. Eggs and sperm did not appear to be irreversibly modified by incubation in seawater solutions containing tetraiodofluorescein (erythrosin B). Sperm binding to the vitelline layer was also inhibited by erythrosin B, but required concentrations greater than that necessary to block fertilization. The ability of the compounds to block fertilization was a function of the particular fluorescein derivative used and its concentration. The concentration required to inhibit fertilization in 50% of the eggs was related to dye lipid solubility. The dyes may inhibit fertilization by preventing gamete membrane fusion.