Time-related effects of intoxication with cadmium and mercury in the red wood ant

Abstract

Biochemical and physiological effects of prolonged feeding of the ant Formica aquilonia, in natural conditions with excess of cadmium or mercury, were studied. In all developmental stages metals caused the time-dependent increase of AMP, parallel with a decrease of ATP and the pool size of adenylates. This was reflected by a low adenylate energy charge (AEC) index and accompanied by an inhibition of ATPases. Despite the fall in the adenylate pool of workers, the levels of adenylate energy charge confirmed their ability to maintain energetic balance. Prolonged access to food highly contaminated with Cd, or Cd with Hg, diminished these adaptive abilities, but pre-adaptive reactions (not correlated with the metal load) were induced. Activity patterns of enzymes involved in energy metabolism showed metal dependent inhibitory effects, but repeated contamination evoked some compensatory mechanisms, both in workers and in the pupal stage from the next generations. Cadmium (indirectly) stimulated the esterases and free radical scavengers. Compensatory mechanisms were insufficient in insects contaminated with both Hg and Cd, even causing family disappearance, through increased mortality and migration to other colonies. Compensatory mechanisms expressed by the adult workers appeared to be of a phenotypic origin