Acquisition of thermotolerance in sea urchin embryos correlates with the synthesis and age of the heat shock proteins.

Preheating at 31 degrees C induces thermotolerance in Paracentrotus lividus embryos, which therefore become able to withstand 1-h treatment at the otherwise lethal temperature of 35 degrees C, and to develop normally. The acquisition of thermotolerance is positively correlated with the amount of heat shock proteins produced during the 31 degrees C treatment. Evidence is provided that the heat shock proteins, although present in the embryo for long periods after synthesis, lose their effect on thermotolerance within 3 h of the cessation of synthesis.