SCN Blocks Hardening of the Fertilization Envelope of Sea Urchin Eggs and Adhesion of Blastomeres.

Sea urchin eggs kept in artificial sea water (ASW) containing 0.01-0.3 M NaSCN in place of NaCI from within 2 min after insemination formed thin, enlarged fertilization envelopes, which were broken on mild agitation of egg suspensions more easily than those formed in Ca -free ASW. The blastomeres of almost all embryos derived from eggs treated with 0.2M SCN for 1 hr dissociated spontaneously, and did not reassociate with other blastomeres appreciably. Thus SCN probably denaturated some compound(s) participating in blastomere binding and hardening of the fertilization envelope. Abnormal arrangements of blastomeres, probably due to incomplete blastomere dissociation, were observed in embryos derived from eggs treated with 0.1 M SCN for 1 hr. Treatment of fertilized or unfertilized eggs with 0.05-0.1 M SCN for a short period caused concentration-dependent block of morphogenic processes such as formation of the archenteron and pluteus arms in the post-hatching period. The effects of SCN on morphogenesis were not inhibited by furosemide or 4,4'-diisothiocyano 2,2'-disulfonic stilbene. Presumably, the denaturation of several compounds in the egg surface by SCN causes abnormal morphogenesis of embryos. The inhibitory effects of SCN on hardening of the fertilization envelope, blastomere binding and morphogenesis were greater in the absence of Ca .