Chapter 20 Induced Fusion of Echinoderm Oocytes and Eggs 1 1 With an Appendix, “Methods for Maintaining Starfish and Obtaining Gametes and Embryos Year Round,” by P. V. Davydov, O. I. Shubravyi, and S. G. Vassetzky.

The chapter reviews the methods of induced fusion of echinoderm oocytes and eggs. It has shown that the procedures leading to the fusion of oocytes or eggs do not affect the normal condition of the cells: they retained the capacity for maturation, fertilization, and subsequent development. The use of the induced fusion method in studies on the echinoderm oocytes and eggs makes it possible to obtain mass quantities of oocytes and eggs combined at different developmental stages or to alter (qualitatively or quantitatively) the nucleocytoplasmic ratio. The technique of induced cell fusion calls for the solution of three problems: (1) the removal of all envelopes peripheral to the plasma membrane—that is, the removal of the follicular envelope and vitelline membrane; (2) the agglutination of the oocytes; and (3) the fusion of the apposed membranes. Therefore, they are conducted at temperatures of 13-2O˚C, in an air-conditioned room when necessary, with the use of artificial seawater. The possibility of egg fusion in echinoderms is corroborated by the spontaneous and rare appearance of fused sea urchin eggs after treatments designed to remove the fertilization membrane.