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Biol Bull 109: 316-327. (October 1955)
© 1955 Marine Biological Laboratory
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DEVELOPMENTAL MODIFICATIONS IN THE SAND DOLLAR CAUSED BY ZINC CHLORIDE AND PREVENTED BY GLUTATHIONE

OLIN RULON 1

1 Dept. of Biological Sciences, Northwestern University, Evanston, Illinois, and the Hopkins Marine Station, Pacific Grove, Calif.

1. Newly fertilized eggs and 6-hour blastulae were exposed to sea water solutions of zinc chloride (M/10,000-M/320,000) for varying intervals of time.

2. It was found that high concentrations inhibited cleavage while low concentrations caused marked changes in the developmental pattern without much effect in cleavage. The continuous exposure of newly fertilized eggs to strong solutions following fertilization resulted in radial, poorly-differentiated larvae but as the strength of the solution decreased the larvae became elongated in the polar direction and differentiated basal ciliated bands. In the weaker solutions, plutei with large ventral areas differentiated. In M/10,000, exogastrulation occurred in 10-25 per cent of the larvae while the differentiation of skeleton was prevented in all concentrations above M/80,000.

3. Continuous treatment after cleavage gave larvae that were but slightly different from those treated continuously from fertilization. The chief differences were that fewer exogastrulae developed, skeleton differentiated in slightly higher concentrations, and stomodaea developed in solutions that had previously been inhibitory (when treatment began with the one-cell stage).

4. Exposure to high and intermediate concentrations for the first 24 hours following fertilization (followed by return to sea water) caused the larvae to show radial symmetry, polar elongation, and the differentiation of apical and basal lobes. Six hours exposure immediately after cleavage was highly effective in causing the development of radial symmetry and polar elongation, as contrasted to exposure during the six-hour period of cleavage which was relatively ineffective.

5. Developing eggs may be protected from the effects of zinc chloride by adding glutathione to the test solutions. Since the effects of zinc are very similar to those of cobalt and selenium it is suggested that part of the effect of zinc in these experiments may be through the inhibition of enzymes with sulfhydryl radicals.






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Copyright © 1955 by the Marine Biological Laboratory.