ON THE CONSERVATION OF CALCIUM WAVE SPEEDS

Most long distance calcium signals are believed to take the form of ac tively propagated calcium waves. In 1991, when this proposal was first advanced, all such waves were thought to belong to one class, for whi ch fertilization waves were the prototype. Moreover, the speeds of suc h waves were found to be conserved at about 10 mu m/s for primary fert ilization waves and 30 mu m/s for waves through fully active systems a t 20 degrees C. In 1993, preliminary evidence for a second class of su ch waves was published and the prototype for these were ones which dri ve cell cleavage. These move at only about 1 mu m/s at 20 degrees C an d were, therefore, called slow calcium waves as opposed to the fast on es first considered. Here we compile compelling evidence that slow wav es comprise a second distinct class of actively propagated calcium wav es. This is based on 30 papers which yield evidence of slow calcium wa ves in organisms ranging from Dictyostelium to mammals and phenomena r anging from the surface contraction waves seen long ago in axolotl egg s to embryonic cleavage and mitotic waves and to ones recently seen to accompany primary neural induction in axolotls. Ultraslow and ultrafa st calcium waves are also considered.