17Fig. 1.2 A Ca2+ wave triggered by the fertilizing sperm in a medaka egg. The wave was visualized
by measuring luminescence of aequorin that was preloaded into the egg’s cortical cytoplasm. The
photographs were taken at 10-s intervals starting 40 s after insemination. The wave started at the
animal pole (AP) and traversed the egg toward the vegetal pole (VP) (From Iwamatsu 2000 , with
permission)
1 Egg Activation at Fertilization