Electron Paramagnetic Resonance Study of the Migratory Ant Pachycondyla marginata abdomens

Electron paramagnetic resonance was used to investigate the magnetic material present in abdomens of Pachycondyla marginata ants. A g ≅ 4.3 resonance of high-spin ferric ions and a very narrow g ≅ 2 line are observed. Two principal resonance broad lines, one with g > 4.5 (LF) and the other in the region of g ≅ 2 (HF), were associated with the biomineralization process. The resonance field shift between these two lines, HF and LF, associated with magnetic nanoparticles indicates the presence of cluster structures containing on average three single units of magnetite-based nanoparticles. Analysis of the temperature dependence of the HF resonance linewidths supports the model picture of isolated magnetite nanostructures of ∼13 nm in diameter with a magnetic energy of 544 K. These particles are shown to present a superparamagnetic behavior at room temperature. The use of these superparamagnetic particle properties for the magnetoreception process of the ants is suggested.