Characterization of Ca2Â + signaling in the external yolk syncytial layer during the late blastula and early gastrula periods of zebrafish development

► A series of Ca2 + waves is propagated within the E-YSL of zebrafish embryos. ► Wave propagation starts at dome stage to 30% epiboly when the E-YSN form clusters. ► Waves are generated via Ca2 + release from IP3Rs, possibly in the perinuclear ER. ► At shield stage, increasing inter-nuclear distances resulted in wave termination. ► Ca2 + waves never propagated in the I-YSL or between the E- and I-YSL.