The effects of hexavalent and trivalent chromium on fertilization and development in sea urchins

The action of Cr⁶⁺ (as chromate) and Cr³⁺ (as sulfate and nitrate) on fertilization and development has been investigated in sea urchins. By rearing the embryos in the presence of chromate (5 × 10^?5 to 5 × 10^?4m), the differentiation of the gut and skeleton was severely affected. The treatment of sperm before fertilization with CrO^2?₄ (10 to 30 min, 10^?4 to 10^?2m) resulted in a number of abnormal larvae, depending on the length of exposure and the CrO^2?₄ concentration. Morphological and quantitative changes of mitotic activity during cleavage were observed as a result of CrO^2?₄ exposure of zygotes, as well as of sperm and egg pretreatment. The exposure of embryos to Cr³⁺ after fertilization permitted larval differentiation, but affected the motility and hatchability of the embryos. The pretreatment of gametes with Cr³⁺ never induced larval malformations. Cr³⁺ exerted a strong depressive action on fertilization by decreasing the fertilizing capacity of sperm and leaving the fertilizability of the eggs almost unaffected.