Morphogenetic agents from unfertilized eggs of the sea urchin Paracentrotus lividus

Abstract

Previous experience points to the conclusion that specific morphogenetic agents form the basis of differentiation in the early development of sea urchins. Attempts have therefore been made to isolate such agents from the unfertilized eggs of the sea urchin, Paracentrotus lividus. By ion-exchange chromatography on Dowex 50 W-X2 of partly purified egg homogenates a fraction was isolated which showed an animalizing action on whole eggs and embryos. When tested on animal and vegetal halves, isolated in the 16- and 32-cell stages, the animalizing effect was considerably increased. The fraction caused a definite extension of the ciliary tuft in animal halves, and it was capable of inducing a differentiation to almost normal plutei on vegetal halves. A treatment for 2 hours was found sufficient to induce the effect if it was applied during the period of competence, i.e., the first 6 hours after the operation. A second fraction eluted from the column in close proximity to the animalizing one caused a vegetalization which, however, was somewhat weaker, particularly when tested on whole eggs and embryos. When animal halves were exposed to animalizing and vegetalizing fractions mixed in certain proportion, a neutralization of their effects was observed.