First evidence of elemental accumulation patterns in the hard tick Dermacentor reticulatus exoskeleton using EDS analysis: Insights into bioindicator potential across diverse habitats in Poland and Ukraine.

Hard ticks are significant disease vectors whose chitinous exoskeletons possess pollutant-absorbing properties. Due to their high trophic position, ticks bioaccumulate persistent toxins, yet this process remains unexplored. This study investigated the exoskeletal chemical composition of Dermacentor reticulatus using SEM-EDS, focusing on metabolic elements and environmental pollutants (including Cd, Al, Sr, Cs, Ca, K, Fe, Ni, Co, Pb, Hg, and Cr). This approach enables precise analysis of biological structures, providing new insights into pollutant accumulation in arthropods. Ticks were analysed from three sampling locations representing contrasting environmental profiles: the urban area of Warsaw (5♂/5♀), the rural area of Kosewo Górne (0♂/10♀) (Poland), and the radionuclide-contaminated Chornobyl area (5♂/5♀) (Ukraine). Regional and biological variations, including differences across exoskeleton zones and between sexes, were also examined. The results revealed regional differences in the chemical composition of tick exoskeletons. Ticks from the Chornobyl exhibited lower concentrations of heavy metals, such as Fe, Co, and Ni (1.98, 0.60, and 0.61 wt%, respectively), compared to those from Kosewo Górne (2.62, 0.79, and 0.74 wt%, respectively). Furthermore, significant variability was identified across anatomical zones; notably, statistically significant differences in Fe concentration were found within zone 3 of CEZ ticks, while the lowest concentrations of Cs (p = 0.0052) and Ca (p = 0.0039) were recorded in zone 2 across all locations. Significant sex-based differences in the occurrence of specific elements were identified in ticks from all study locations. This study provides the first evidence of variability in the accumulation of selected elements across D. reticulatus tick exoskeleton. These findings establish a foundation for further research into the influence of environmental pollutants on tick physiology and vector competence, offering potential for a more comprehensive characterization of exoskeleton composition and its functional implications. These patterns suggest D. reticulatus exoskeletons may serve as sensitive bioindicators of environmental pollution across diverse habitats.