The Modification of Developmental Patterns in the Sand Dollar with Sodium Azide

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Abstract
Newly fertilized eggs and 6-hour blastulae of Dendraster excentricus were exposed to [image]/200-[image]/800 sodium azide (made up in sea water) for periods ranging from 6 to 60 hrs. Blastulae were better able to tolerate continuous exposure to the agent and gave better recovery on return to sea water than newly fertilized eggs. With continuous exposure to [image]/800, beginning at the 1-cell stage, over 50% developed into entodermized exogastrulae. Differential recovery of ventral ectoderm occurred following 6 and 18 hrs. initial exposure of newly fertilized eggs to [image]/800. Approx. 90% exogastrulation (with entodermization in the higher concns.) occurred following 18 hrs. exposure of newly fertilized eggs to [image]/400-[image]/800. Differential recovery of ventral regions '' occurred following 12 hrs. exposure of blastulae to [image]/200. Blastulae exposed for 36 hrs. to [image]/200 (followed by return to sea water) developed chiefly into highly entodermized forms with little or no ectodermal differentiation. The presence of gradients of cytochrome oxidase and the possible role of different enzyme inhibitors in modifying developmental patterns in the echinoderm egg were discussed.