ACCUMULATION OF EADIOACTIVE CALCIUM TN LARVAE OF THE SEA URCHIN PSEUDOCENTROTUS DEPRESSUS

Abstract
The uptake of radioactive calcium by sea urchin larvae was investigated. Up to the biastula stage, calcium uptake proceeds at an extremely low rate, while it increases greatly during gastrulation. Autoradiographs of whole larvae show the increase of calcium uptake in parallel with the formation of the spicule. Before appearance of the spicular rudiment, however, calcium uptake increases at the mesenchyme blastuba stage. Autoradiographs of sections show that penetrated calcium is distributed in the hiastocoeb. It is assumed that calcium is concentrated in the blastocoel before deposition on the spicule.

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