DEVELOPMENTAL MODIFICATIONS IN THE SAND DOLLAR CAUSED BY ZINC CHLORIDE AND PREVENTED BY GLUTATHIONE

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Abstract
Newly fertilized eggs and 6-hour blastulae of Dendraster excentricus were treated with sea water solutions of ZnCl2 (M/10,000-M/320,000). Eggs, treated for 6 hours with high concentrations, developed chiefly into stunted, bilateral larvae while similar treatment of blastulae resulted chiefly in radial larvae, elongated in the polar direction. Treatment of both stages to high and intermediate concentrations for 18-24 hours usually caused the larvae to show radial symmetry, polar elongation, and differentiation of apical lobes. Under certain conditions stomodaea differentiated at the apical ends. Continuous treatment with strong solutions resulted chiefly in radial, cell-filled gastrulae; with intermediate concentrations in thin-walled, radial forms with large, basal, ciliated bands; and with weak solutions in bilateral plutei with enlarged ventral areas. Eggs and blastulae were protected from the effects of ZnCl2 by adding glutathione to the test solutions.