Effects of Cadmium on Developing Eggs of the Pacific Herring with Particular Reference to Carbon Dioxide Fixing Enzymes

Abstract

The effect of 10 ppm of cadmium on eggs of the Pacific herring, Clupea pallasii, incubated in sea water of 20 percent salinity at 5/sup 0/C was examined at five stages of development. Eggs exposed to cadmium hatched approximately 10 days earlier than those of the control; the percentage of viable hatch was 82.0 in the control and 27.3 for eggs exposed to cadmium; the average size of viable larvae was 8.46 and 5.49 mm respectively. Like the garpike, cadmium uptake by herring eggs reached its maximum early in the incubation period and was maintained throughout the 5 developmental stages studied; the total uptake was, however, much greater than that reported for Baltic herring. The relative activity of all four carbon dioxide fixing enzymes studied was depressed by exposure to cadmium; propionyl CoA carboxylase was depressed before flattening of the blastodisc stage; PEP carboxykinase depression started prior to closure of the blastopore, whereas NAD- and NADP-malic enzymes were depressed only prior to the hatching stage. It is postulated that the relatively small larvae hatching from eggs exposed to cadmium may be the result of: (1) depression of the relative activity of the carbon dioxide fixing enzymes at different stages ofmore » development, and/or (2) cadmium being bound to the chorion making it vulnerable, thus producing earlier hatching and premature larvae.« less