title: Stage sensitivity of eggs of the teleost Oryzias latipes to cadmium exposure.
abstract: The stage sensitivity of eggs of the teleost Oryzias latipes to cadmium exposure was examined. First, using eggs at the blastula stage, the proper concentration of cadmium to which the eggs should be exposed was estimated. The eggs were, therefore, exposed to cadmium solutions ranging from 10.0 to 300.0 mg Cd/liter for 1 hr, and then they were transferred to cadmium-free medium. The cumulative mortality of the eggs was estimated by counting dead eggs within 24 hr. Mortality (1.1 +/- 0.7%) indistinguishable from that of the control (1.0 +/- 0.2%) was obtained in the solution of 10.0 mg Cd/liter. Relatively higher mortalities of 13.2 +/- 1.5, 18.0 +/- 1.0, and 20.7 +/- 3.1% could be seen in the solutions containing 50.0, 100.0, and 150.0 mg Cd/liter, respectively. Moreover, the exposure of the eggs to 200.0 and 300.0 mg Cd/liter increased mortality rates to 32.0 +/- 0.8 and 34.7 +/- 2.4%, respectively. Consequently, the concentration of 200.0 mg Cd/liter was selected for examining the stage sensitivity. Eggs at 11 different developmental stages were exposed to cadmium at a concentration of 200.0 mg Cd/liter for 1 hr. The mortalities obtained at the 4- to 16-cell stage, 32-cell stage, and morula stage were 99.2 +/- 1.0, 97.4 +/- 2.6, and 89.6 +/- 10.6%, respectively. With the progress of embryonic development, the eggs became more resistant to cadmium toxicity. After the morula stage, the mortalities decreased abruptly. In order to ascertain whether the change in mortalities of the eggs with development was related to the amount of cadmium combined with the eggs, the cadmium content was determined. In contrast to the remarkable change in the stage sensitivity to cadmium, the curve of cadmium content in the eggs remained constant at about 520 ng/egg throughout the experimental period.
mesh_terms: D000818:Animals; D002104:Cadmium / Q000378:metabolism / Q000633:toxicity*; D003532:Cyprinodontiformes / Q000196:embryology*; D005260:Female; D008297:Male; D009990:Oryzias / Q000196:embryology* / Q000378:metabolism; D010063:Ovum / Q000187:drug effects / Q000528:radiation effects
chemical_list: D002104:Cadmium