The Time-Course of Hatching Enzyme Secretion in the Sea Urchin Strongylocentrotus purpuratus: (Timing/secretion/hatching enzyme).

By two independent methods, we have determined approximately the time-course of hatching enzyme secretion in the sea urchin Strongylocentrotus purpuratus. A quick-kill method indicates that a significant fraction of the enzyme is secreted between 90% and 97% of the fertilization-hatching interval. A direct assay method indicates that the remainder of the enzyme is secreted on either side of the 90-97%"window". The entire period of secretion spans from 75% to 100% or more of the fertilization-hatching interval. For embryos raised at 15°C this translates to an interval of 4.8 or more hr.