Stores iron in a soluble, non-toxic, readily available form. Important for iron homeostasis. Has ferroxidase activity. Iron is taken up in the ferrous form and deposited as ferric hydroxides after oxidation (By similarity). 4 Fe(2+) + 4 H(+) + O2 = 4 Fe(3+) + 2 H2O Oligomer of 12 or 24 subunits. The functional molecule is roughly spherical and contains a central cavity into which the polymeric ferric iron core is deposited (By similarity). Midgut gland and bloodstream. First detected during pregastrulation stage, levels increase up to the hatching stage, and is still present at the late veliger stage. Contains an 'insertion' sequence of 42 residues which is not present in other ferritins. Belongs to the ferritin family.