Zinc and cadmium regulation efficiency in three ant species originating from a metal pollution gradient

Highly efficient accumulation of trace metals is often reported in ants, but their metal regulation strategies are poorly understood. This study examined the relationships between Zn and Cd total (tot) and water soluble (ws) concentrations in soil and in workers of three ant species collected along a metal-pollution gradient: Formica cunicularia, Lasius flavus and Myrmica rubra. Regression line comparisons showed the body loads of metals to depend strongly on the metal and the species. M. rubra showed the most efficient regulation of Zn, as its average Zn concentration and the regression slope were several times lower than for the other species. Although the species differed in their Cd levels, the slopes of the relationships between Cd concentration in soil and in ants did not differ between species (tot: p = 0.71, ws: p = 0.31). The very weak relationship for Cd found for all species suggests at least some active Cd regulation. These results can be explained in the context of tissue-specific metal accumulation. High Zn accumulation in mandibles and ovarioles may explain its high accumulation in F. cunicularia and L. flavus.