This survey focuses on early or primitive developmental phenomena for which
the location of a steady high calcium region or the direction of a calcium
wave is critical and calcium is more than a trigger. It starts with the lo
ng studied roles of calcium in fucoid eggs and in Dictyostelium and progres
ses to newer work on high calcium regions in medaka fish, zebrafish, and Dr
osophila eggs. It then proposes that propagated, ultraslow developmental wa
ves in six diverse systems indicate a new and important class of calcium wa
ves. These include the morphogenetic furrow in Drosophila eye discs, floret
formation in sunflowers, DNA replication waves in protozoan macronuclei, g
rowth-cone like waves in hippocampal neurons, and two others. It then consi
ders the possible organizing roles of slow calcium waves. Here, it emphasiz
es surface contractile waves during primary neural induction and elsewhere
as well as the possibility of cellular peristalsis. Finally, it reviews the
organizing roles of fast calcium waves in ascidian eggs. BioEssays 21.657-
667, 1999. (C) 1999 John Wiley & Sons, Inc.