Elemental composition of biomineralized amorphous mineral granules isolated from ants: correlation with ingested mineral particles from the soil.
Amorphous mineral granules are formed by concentric mineral layers containing polyphosphate, pyrophosphate and/or orthophosphate and several metallic cations such as Mg(2+), Ca(2+), K(+), Mn(2+), Fe(3+), Cu(2+), and Zn(2+). In this work, we analyzed amorphous mineral granules isolated from the ant species Camponotus abdominalis, Camponotus sp., Acromyrmex subterraneus and Pachycondyla marginata by energy-dispersive X-ray analysis. The elemental composition of the granules was compared to that of mineral particles, probably soil particles, to access the influence of the environment and of specific characteristics of each ant species in the elemental composition of the amorphous mineral granules. Both the granules and mineral particles presented Mg, Ca, Fe, and Zn in the four species. Additionally, Al tended to be present in both (or none) of the two types of material in a given ant species, suggesting that the aluminum found in the amorphous mineral granules could be derived from ingested soil particles. On the other hand, Sr was found in the amorphous mineral granules of some of the studied ant species, but not in the mineral particles. The fact that 3/4 of the elements found in the granules were found also in the mineral particles suggests that the mineral composition of the soil plays a fundamental role in the accumulation of some elements in the amorphous mineral granules of ants. These results suggest a major role of soil particles as a source of micronutrients for the four ant species.