Cadmium toxicokinetics differ between forest and city colonies of the ant Temnothorax nylanderi (Formicidae: Myrmicinae) (Foerster, 1850).

City environments are often contaminated with trace metals, such as cadmium, posing significant risks to organisms. However, how these contaminants accumulate in social groups like ants remains understudied. In this experiment, we compared the temporal kinetics of cadmium accumulation and elimination in colonies of the ant Temnothorax nylanderi exposed to the same cadmium concentration but originating from two contrasting habitat types: unpolluted (forest) and polluted (city). Ant colonies were given cadmium-laced food during a contamination phase, followed by uncontaminated food during a decontamination phase, under controlled laboratory conditions. The internal cadmium concentration in ants increased quickly during the contamination phase and reached a plateau. During the decontamination phase, the internal cadmium concentration decreased sharply. Although the global toxicokinetics showed a similar pattern in both habitat types, the plateau was lower in the city than forest habitats. This suggests a more efficient regulation of internal cadmium concentration in colonies living in polluted areas, associated with uptake and not elimination. These findings support the idea that city colonies may have developed enhanced tolerance to cadmium exposure by decreasing their level of contamination for a given contaminated food source. Further studies are needed to investigate the long-term ecological and evolutionary implications of these mechanisms and their relevance for ecosystem pollution monitoring based on ant contamination.