A new model for the formation of earthworms granules

Understanding the mechanisms of nucleation, stabilization and aggregation of amorphous calcium carbonate (ACC) and factors controlling its further transformation into crystalline phases is fundamental for elucidation of biogenic mineralization.

Some species of earthworms create millimeter-sized calcareous granules from amorphous calcium carbonate, which crystallize to a more stable mineral phase (mostly calcite). This study investigates the mechanisms of ACC stabilization by the incorporation of trace elements, like manganese, and the ulterior precipitation of calcareous granules by a coupled process of amorphous particle attachment and ion-by-ion growth. The study highlights also potential threat that chemical pollution of soil poses to the normal development of earthworm granules.