Effect of cadmium and ration level on oxygen consumption, RNA concentration and RNA-DNA ratio in two clones of Daphnia magna Straus

Abstract

The rate of oxygen consumption, or respiration rate, of Daphnia magna is elevated as the food concentration of its environment increases, a phenomenon referred to as specific dynamic action (SDA). A possible cause of this response, the cost of tissue synthesis, was investigated using RNA concentration and RNA-DNA ratio as indices. The effects of cadmium on SDA was studied, to establish whether toxicants affect SDA either by increasing the rate of protein synthesis (for the repair/replacement of stress-damaged proteins), and/or by reducing feeding rate. Using two different genotypes, previously shown to differ in their sensitivities to cadmium, the possibility of genetic variation in response was also addressed.